Machine picking in cotton is an emerging practice in India,to solve the problems of labour shortages and production costs increasing.Cotton production has been declining in recent years;however,the high density planti...Machine picking in cotton is an emerging practice in India,to solve the problems of labour shortages and production costs increasing.Cotton production has been declining in recent years;however,the high density planting system(HDPS)offers a viable method to enhance productivity by increasing plant populations per unit area,optimizing resource utilization,and facilitating machine picking.Cotton is an indeterminate plant that produce excessive vegeta-tive growth in favorable soil fertility and moisture conditions,which posing challenges for efficient machine picking.To address this issue,the application of plant growth retardants(PGRs)is essential for controlling canopy architecture.PGRs reduce internode elongation,promote regulated branching,and increase plant compactness,making cotton plants better suited for machine picking.PGRs application also optimizes photosynthates distribution between veg-etative and reproductive growth,resulting in higher yields and improved fibre quality.The integration of HDPS and PGRs applications results in an optimal plant architecture for improving machine picking efficiency.However,the success of this integration is determined by some factors,including cotton variety,environmental conditions,and geographical variations.These approaches not only address yield stagnation and labour shortages but also help to establish more effective and sustainable cotton farming practices,resulting in higher cotton productivity.展开更多
Background Thidiazuron(TDZ)is a widely used chemical defoliant in commercial cotton production and is often combined with the herbicide Diuron to form the commercial defoliant mixture known as TDZ·Diuron(T·D...Background Thidiazuron(TDZ)is a widely used chemical defoliant in commercial cotton production and is often combined with the herbicide Diuron to form the commercial defoliant mixture known as TDZ·Diuron(T·D,540 g·L^(-1)suspension).However,due to increasing concerns about the environmental and biological risks posed by Diuron,there is an urgent need to develop safer and more effective alternatives.Jasmonic acid(JA)and its derivatives are key phytohormones in organ senescence and abscission.Results Greenhouse experiments at the seedling stage revealed that Me-JA(0.8 mmol·L^(-1))alone did not induce defoliation.However,its co-application with TDZ(0.45 mmol·L^(-1))at concentrations of 0.6,0.8,and 1.0 mmol·L^(-1)significantly enhanced defoliation efficacy.The most effective combination—TDZ with 0.8 mmol·L^(-1)Me-JA—achieved a 100%defoliation rate at 5 days after treatment(DAT),23.7 percentage points higher than TDZ alone,and comparable to the commercial TDZ·Diuron formulation with equivalent TDZ content.Field trials conducted in Beijing(Shangzhuang),Hebei(Hejian),and Xinjiang(Shihezi)confirmed that the combination of 0.6 mmol·L^(-1)Me-JA with 1.70 mmol·L^(-1)TDZ provided optimal defoliation performance.At 21 DAT,the defoliation rate increased by 13.5–16.3 percentage points compared with TDZ alone.Furthermore,boll opening rates improved by 5.7–12.7 percentage points relative to TDZ-only treatments.Phytohormonal analyses from the Shangzhuang site showed that the combined treatment significantly altered hormone levels in both leaves and petioles.Compared with TDZ alone,the mixture reduced concentrations of auxin(IAA),cytokinins(Z+ZR,iP+iPA,DHZ+DHZR),and gibberellic acid(GA3),while increasing levels of JA,abscisic acid(ABA),and brassinosteroids(BR).These hormonal shifts may underlie the enhanced defoliation observed with the combined treatment.Importantly,the TDZ-Me-JA combination did not adversely affect cotton yield,yield components,or fiber quality.Conclusion The combination of Me-JA and TDZ has a good defoliation effect without affecting crop yield or fiber quality.And it provides a promising foundation for the development of novel,environmentally friendly cotton defoliants.展开更多
Forest ecosystems within national parks are threatened by various biotic and abiotic factors.To deter-mine the causes of the desiccation and death of trees in mixed coniferous and deciduous forests of Tara National Pa...Forest ecosystems within national parks are threatened by various biotic and abiotic factors.To deter-mine the causes of the desiccation and death of trees in mixed coniferous and deciduous forests of Tara National Park(TNP),Serbia,we monitored defoliation and mortality of individual trees in permanent experimental plots.Data on the desiccation of a large number of trees were gathered by determining the total volume of dry trees and areas of forests under drying stress.The two sets of data were combined to determine the impact of climatic events,primarily drought periods,on the desiccation of forests.Combining data from the International Co-operative Program on Assessment and Monitoring of Air Pollution Effects on Forests(ICP Forests)with TNP data helped relate forest desiccation to climate events.Key climate signals were identified by monitoring tree defoliation changes in two permanent experimental plots,and then assessed for their influence on tree desicca-tion in the entire national park.The standardized precipita-tion evapotranspiration index(SPEI)was used for a more detailed analysis of the drought period.Despite the lack of climate data for a certain period,the SPEI index revealed a link between climate variables and the defoliation and desic-cation of forests.Furthermore,the desiccation of trees was preceded by a long drought period.Although mixed conifer-ous-deciduous forests are often considered less vulnerable to natural influences,this study suggests that forest ecosystems can become vulnerable regardless of tree species composi-tion due to multi-year droughts.These findings contribute to a better understanding of important clues for predicting pos-sible future desiccation of forests.Continuous monitoring of the state of forests and of more permanent experimental plots in national parks could provide better quality data and timely responses to stressful situations.展开更多
Leaves are important‘source’organs that synthesize organic matter,providing carbon sources for plant growth.Here,we used Populus talassica×Populus euphratica,the dominant species in ecological and timber forest...Leaves are important‘source’organs that synthesize organic matter,providing carbon sources for plant growth.Here,we used Populus talassica×Populus euphratica,the dominant species in ecological and timber forests,to simulate carbon limitation through artificial 25%,50%,and 75%defoliation treatments and explore the effects on root,stem,and leaf morphology,biomass accumulation,and carbon allocation strategies.At the 60th d after treat-ment,under 25%defoliation treatment,the plant height,specific leaf weight,root surface area and volume,and concentrations of non-structural carbohydrates in stem and root were significantly increased by 9.13%,20.00%,16.60%,31.95%,5.12%,and 9.34%,respectively,relative to the control.There was no significant change in the growth indicators under 50%defoliation treatment,but the concentrations of non-structural carbohydrates in the leaf and stem significantly decreased,showing mostly a negative correlation between them.The opposite was observed in the root.Under 75%defoliation treatment,the plant height,ground diameter,leaf number,single leaf area,root,stem,and total biomass were significantly reduced by 14.15%,10.24%,14.86%,11.31%,11.56%,21.87%,and 16.82%,respectively,relative to the control.The concentrations of non-structural carbohydrates in various organs were significantly reduced,particularly in the consumption of the starch concentrations in the stem and root.These results indicated that carbon allocation strategies can be adjusted to increase the con-centration of non-structural carbohydrates in root and meet plant growth needs under 25%and 50%defoliation.However,75%defoliation significantly limited the distribution of non-structural carbohydrates to roots and stems,reduced carbon storage,and thus inhibited plant growth.Defoliation-induced carbon limitation altered the carbon allocation pattern of P.talassica×P.euphratica,and the relationship between carbon reserves in roots and tree growth recovery after defoliation was greater.This study provides a theoretical basis for the comprehen-sive management of P.talassica×P.euphratica plantations,as well as a reference for the study of plantation car-bon allocation strategies in the desert and semi-desert regions of Xinjiang under carbon-limitation conditions.展开更多
Ice storms can cause substantial damage to tree crowns and lead to growth reduction.However,in uneven-aged stands,the growth of an individual tree may also increase due to crown release caused by the damage or mortali...Ice storms can cause substantial damage to tree crowns and lead to growth reduction.However,in uneven-aged stands,the growth of an individual tree may also increase due to crown release caused by the damage or mortality of neighboring trees.Three years after the devastating ice storm in 2014 in mixed uneven-aged Dinaric forests(Croatia),we cored 156 European beech(Fagus sylvatica)and 85 silver fir(Abies alba)trees across 20 permanent sample plots to study the post-storm growth response as a function of tree,stand,site,spatial arrangement and local competition factors.The ice storm damaged over 84% of trees on the sampled plots.Among the cored trees,52.7% exhibited growth reduction,which on average amounted to3.1%relative to the pre-disturbance average.Trees with less than 40% crown damage maintained their pre-disturbance growth rates or experienced only minor growth suppression.While 60% of beech trees suffered a growth reduction at an average rate of 7.2%,the average radial increment of fir after the storm was 14.0% higher compared to the pre-storm rate.A linear mixedeffects model suggests that the growth response can largely be explained by the focal and neighboring tree species identity,tree competition pressure,focal and neighboring tree damage,crown size,slenderness index and stoniness.Growth release was positively associated with fir,inverse distance-weighted crown damage of the nearest neighbor,shorter crowns,slenderness,less stony sites and less damaged trees.The analysis suggests that at the same level of local competition load,trees with a broadleaved and damaged nearest neighbor are more likely to experience growth release than those with a coniferous or undamaged nearest neighbor.This implies that unevenaged stands with a substantial presence and mingling of both conifers and broadleaves are expected to be more resilient to ice storms and are less likely to suffer growth reduction.展开更多
Modern agronomic concepts such as high-density planting systems are emerging in cotton-based cropping systems. Agronomic practices specific to new cotton varieties made in specific niches, management of the vegetation...Modern agronomic concepts such as high-density planting systems are emerging in cotton-based cropping systems. Agronomic practices specific to new cotton varieties made in specific niches, management of the vegetation cover using growth regulators (retardants and defoliants) for better quality and above all the improvement of crop health through integrated nutrient management with an emphasis on the foliar feeding pattern, can significantly increase cotton productivity and improve the socio-economic status of farmers of cotton. It is in this context that studies on cotton sowing densities, the supplementation of mineral fertilization with trace elements and the management of the resumption of vegetation of cotton plants at the end of the cycle have been carried out in a farming environment and in research stations. The results of the survey in the farmer’s environment, of the trials conducted in stations and on observation posts showed a positive correlation between sowing densities and seed cotton yield. About 22% of the variations in seed cotton yield are related to sowing density. The best seed cotton yields are obtained with the high sowing densities in the north and the low densities in the south of the Ivorian cotton basin. Studies on the supplementation of base fertilizer with trace elements have shown that the combined application of 200 kg/ha of NPK + 50 kg/ha of urea + 2 kg/ha of ZnS04 increases the seed cotton yield and provides a monetary gain of 36,622 CFA francs/ha. The study on the management of vegetation resumption at the end of the cycle showed that the application of 4 l/ha of Ethephon and 62.5 ml/ha of Diuron at 100 days after emergence improves defoliation and capsule opening for better management of vegetation recovery at the end of the season. Studies have shown that seeding density is a factor in seed cotton yield. Seed cotton yields were improved by supplementing with mineral fertilizer with zinc and adding desiccants and defoliants at the end of the cycle.展开更多
[ Objective ] The research aimed to discuss the occurrence regularity of apple early defoliation disease and control effects of fungicides in west Sichuan plateau. [ Method ] Apple early defoliation disease in west Si...[ Objective ] The research aimed to discuss the occurrence regularity of apple early defoliation disease and control effects of fungicides in west Sichuan plateau. [ Method ] Apple early defoliation disease in west Sichuan plateau was systematically investigated during 2009 and 2011, and the control effects of different fungicides during different spraying periods were studied. [ Result] The species of pathogen mainly was Marssonina ma/i （ P. Henn）, accounting for 32.5%, Phyl-losticta Pirina Sa accounted for 29.9%, and Alternaria mali Roberts accounted for 25.7%. The field fluctuation regularity was as follows ： the disease generally be- gan in the mid-May and ended in early and middle October with only one damage peak during the whole year, the fluctuation had positive correlation with rainfall （ R2 =0.891 8 ＊ ＊ ）. Control test showed that 40% flusilazole had the best control effect （86.5%）, which was best to apply after anthesis. [ Conclusion ] The paper provided theoretical basis for the effective control against apple early defoliation disease.展开更多
[Objective] It aimed to find an optimum condition for compensatory growth of peony.[Method] The different defoliation intensies and frequencies of penoy were implemented to observe accumulated aboveground biomass, reg...[Objective] It aimed to find an optimum condition for compensatory growth of peony.[Method] The different defoliation intensies and frequencies of penoy were implemented to observe accumulated aboveground biomass, regenerated bud number,stem-leaf ratio and the chlorophyll concentration change in residual leaves.[Result] When the defoliation frequency was conducted every 20 d once and defoliaton intensity was from 40%-60%,the accumulated biomass was biggest, when the defoliation frequency was conducted every 10 d once and defoliation intensity was from 60%-80% the regenerated bud number was maximum.The stem-leaf ratio of mild and moderate defoliation intensities(20%-60%) was significantly lower than that of control group.When the defoliation frequency was conducted every 20 d once and defoliation intensity was from 40%-60%,the chlorophyll concentration in residual leaves was obviously higher than that of control group.[Conclusion] The proper defoliation intensity(60%) and lower defoliation frequency(defoliation was conducted every 20 d once) were most favorable to the growth and regenerated of peony which was the compensatory growth.展开更多
Objective:To determine the biological effects of essential oils(EOs) isolated from Cymbopogon iiardus,Cymbopogon Jlexuosus and Cvrnbopogon marlinii grown in Colombia against two Lepidoptera larvae,common pests in the ...Objective:To determine the biological effects of essential oils(EOs) isolated from Cymbopogon iiardus,Cymbopogon Jlexuosus and Cvrnbopogon marlinii grown in Colombia against two Lepidoptera larvae,common pests in the oil palm.Methods:Specimens were captured in the field and the antifeedant activity and dermal contact lethality of EOs were measured against Acharia fusca and Euprosterna elaeasa(Lepidoptera:I.imacodidae) at various concentrations 0.002-0.600 μL/cm^3 and 0.002-8 μL/g,respectively.Results:All EOs exhibited strong antifeedant and toxicity activity toward Acharia fusca and Euprosterna elaeasa larvae.Cymbopogon marlinii oil was llie most active againsl both pest insect species,although all tested EOs were better than the synthetic;repellent IR535 on both insects.Conclusions:Colombian EOs have potential for integrated pest management programs in the oil palm industry.展开更多
The aim of this study was to elucidate the effects of different machine-harvested cotton-planting patterns on defoliation,yield,and fiber quality in cotton and to provide support for improving the quality of machine-h...The aim of this study was to elucidate the effects of different machine-harvested cotton-planting patterns on defoliation,yield,and fiber quality in cotton and to provide support for improving the quality of machine-harvested cotton.In the 2015 and 2016 growing seasons,the Xinluzao 45(XLZ45)and Xinluzao 62(XLZ62)cultivars,which are primarily cultivated in northern Xinjiang,were used as study materials.Conventional wide-narrow row(WNR),wide and ultra-narrow row(UNR),wide-row spacing with high density(HWR),and wide-row spacing with low density(LWR)planting patterns were used to assess the effects of planting patterns on defoliation,yield,and fiber quality.Compared with WNR,the seed cotton yields were significantly decreased by 2.06–5.48%for UNR and by 2.50–6.99%for LWR,respectively.The main cause of reduced yield was a reduction in bolls per unit area.The variation in HWR yield was–1.07–1.07%with reduced bolls per unit area and increased boll weight,thus demonstrating stable production.In terms of fiber quality indicators,the planting patterns only showed significant effects on the micronaire value,with wide-row spacing patterns showing an increase in the micronaire values.The defoliation and boll-opening results showed that the number of leaves and dried leaves in HWR was the lowest among the four planting patterns.Prior to the application of defoliating agent and before machine-harvesting,the numbers of leaves per individual plant in HWR were decreased by 14.45 and 25.00%on average,respectively,compared with WNR,while the number of leaves per unit area was decreased by 27.44 and 36.21%on average,respectively.The rates of boll-opening and defoliation in HWR were the highest.Specifically,the boll-opening rate before defoliation and machine-harvesting in HWR was 44.54 and 5.94%higher on average than in WNR,while the defoliation rate prior to machine-harvesting was 3.45%higher on average than in WNR.The numbers of ineffective defoliated leaves and leaf trash in HWR were the lowest,decreased by 33.40 and 32.43%,respectively,compared with WNR.In conclusion,the HWR planting pattern is associated with a high and stable yield,does not affect fiber quality,promotes early maturation,and can effectively decrease the amount of leaf trash in machine-picked seed cotton,and thus its use is able to improve the quality of machine-harvested cotton.展开更多
Timing of harvest is critical for mechanical picking in cotton production, especially in those regions with double cropping system. Appropriate and safe harvest aids will improve timing and facilitate harvest of cotto...Timing of harvest is critical for mechanical picking in cotton production, especially in those regions with double cropping system. Appropriate and safe harvest aids will improve timing and facilitate harvest of cotton in the double cropping system. Three defoliants （dimethipin, thidiazuron, and thidiazuron-diuron） and one boll opener （ethephon） were included in this research. They were evaluated for their effects on defoliation, boll opening, seedcotton yield, seed quality, and fiber quality of field grown cotton when used alone or as a mixture in 2009 and 2010. Defoliation and/or boll opening were increased by all three defoliants and ethephon, especially by mixtures of a defoliant and ethephon. First harvest of seedcotton was significantly increased with defoliant-ethephon mixtures. No significant adverse effects were observed on boll weight, lint percentage, seed quality, and fiber properties. It was estimated that tank mixes of ethephon and one of the three defoliants can improve the adjusted gross revenue. Boll opening can be used as an alternative indicator for the adjusted gross revenue, because, it was linearly and positively correlated with the relative adjusted gross revenue and convenient in measurements. Wheat seedling growth was not affected by thidiazuron, whereas its seedling emergence, root dry weight, relative water content, and electrolyte leakage were adversely affected by dimethipin and thidiazuron- diuron when concentration was above 340 and 100 g （a.i.） ha-1, respectively. 90% defoliation and 80% boll opening were observed with the high rate of thidiazuron-ethephon mixture, but no adverse effects on winter wheat. The results suggested that tank mixes of ethephon with thidiazuron can be used effectively and safely in the cotton-winter wheat double cropping system to improve yield without adverse effects on seed quality and fiber quality.展开更多
Identifying a superior soybean variety with high defoliator resistance is important to avoid yield loss. Cotton bollworm(Helicoverpa armigera Hübner) is one of the major defoliators of soybean(Glycine max [L.] Me...Identifying a superior soybean variety with high defoliator resistance is important to avoid yield loss. Cotton bollworm(Helicoverpa armigera Hübner) is one of the major defoliators of soybean(Glycine max [L.] Merr.) worldwide. In this study, we evaluated the effect of H. armigera larvae on ED059, a wild soybean(Glycine soja Sieb. et Zucc.), and three cultivated soybean varieties: Tianlong 2, PI 535807, and PI 533604, in choice and no-choice assays. The percentage of ED059 leaflets consumed by H. armigera was lower than that of the three cultivated soybeans. Larvae that fed on ED059 exhibited low weight gain and high mortality rate.Waldbauer nutritional indices suggested that ED059 reduced the growth, consumption, and frass production of H. armigera larvae. Larvae that fed on ED059 showed lower efficiency of conversion of ingested and of digested food than those that fed on Tianlong 2 and PI 533604.However, they showed statistically similar consumption index and approximate digestibility compared with those fed on the three cultivated soybeans. Quantitative real-time PCR analysis revealed that 24 h after insect attack, ED059 had higher transcript levels of Kunitz trypsin inhibitor 3, Cysteine proteinase inhibitor 2, and Nerolidol synthase 1 but a lower transcript level of Pathogenesis-related protein 1 than Tianlong 2. The gene expression results were consistent with the presence of higher levels of jasmonic acid(JA) and transcript levels of the JA biosynthesis enzyme allene oxide cyclase 3 in ED059 than in Tianlong 2. Our findings indicate that ED059 is a superior soybean line with strong insect resistance that may be mediated via the JA pathway.展开更多
Defoliation is an indispensable step in cotton production with mechanical harvesting,especially in the North China Plain(NCP)where mechanical harvesting is limited by a large proportion of green leaves and unopened bo...Defoliation is an indispensable step in cotton production with mechanical harvesting,especially in the North China Plain(NCP)where mechanical harvesting is limited by a large proportion of green leaves and unopened bolls at harvest time due to insufficient thermal resources.It is essential to quantify the optimal use of defoliation products while minimizing yield and quality loss in China.The objective of this study was to test the effect of a new defoliant Xinsaili(XSL,a compound of 10% thidiazuron and 40% ethephon)on the spatial distribution of cotton leaves and bolls,yield and quality in the NCP.There were four treatments:XSL 1800 m L ha^(-1),XSL 2700 m L ha^(-1),XSL splitted into two equal applications(1350 m L ha^(-1) for each),and XSL-free(water)control.Field experiments were conducted in Hebei,China in 2016-2017.All the defoliant treatments did not significantly affect cotton yield and fiber quality compared with the water control.At harvest time,the rate of open bolls under XSL 2700 m L ha^(-1) was 13.5% higher than that under XSL-free control,while the other two treatments showed no significant difference,across the two years.Defoliation percentage of the three XSL treatments showed no difference,but they were on average 42.2% higher than that of XSL-free control.The year-round effect of the defoliant XSL was significant,indicating that climate factors would affect its application.It was concluded that the optimal dose of XSL in the NCP was 2700 m L ha^(-1),and it was unnecessary to split it into two applications.These results would promote cotton mechanical harvesting and reduce the labor cost of cotton production in China.展开更多
Early maturity, complete defoliation and boll opening are essential for the efficient machine harvesting of cotton. Chemical topping, involving one extra application of mepiquat chloride(MC) in addition to its traditi...Early maturity, complete defoliation and boll opening are essential for the efficient machine harvesting of cotton. Chemical topping, involving one extra application of mepiquat chloride(MC) in addition to its traditional multipleapplication strategy, may be able to replace manual topping. However, it is not known whether this chemical topping technique will influence maturity or cotton responses to harvest aids. In this 2-yr field study, we determined the effects of the timing of chemical topping using various rates of MC on boll opening percentage(BOP) before application of harvest aids(50% thidiazuron··ethephon suspension concentrate, referred to as TE), and the defoliation percentage(DP) and BOP 14 days after TE application. The results indicated that late chemical topping(near the physiological cutout, when the nodes above white flower is equal to 5.0) significantly decreased BOP before TE by 5.9–11.2% compared with early(at peak bloom) or middle(seven days after peak bloom) treatments in 2019, which was a relatively normal year based on crop condition. Also, a high MC rate(270 g ha) showed a significantly lower(22.0%) BOP before TE than low(90 g ha) or medium(180 g ha) rates. In 2020, which was characterized by stronger vegetative growth in the late season, the late chemical topping reduced the number of leaves before TE application relative to early or middle treatments, but had lower DP(23.2–27.2%) 14 days after TE application. The high MC rate showed a leaf count before TE application that was similar to the low and medium rates, but it showed the most leaves after TE and much lower(15.0–21.7%) DP in 2020. These results suggest that late timing of chemical topping and a high MC rate decreased the sensitivity of leaves to harvest aids. Further analysis indicated that the late chemical topping mainly affected the leaf drop from the mainstem and fruiting branches where the late regrowth occurred, and the high MC rate reduced leaf shedding from these parts and also from the vegetative branches. In conclusion, chemical topping with MC during the bloom period affected cotton maturity and responses to harvest aids in different ways according to the crop condition. To avoid the risks of delayed maturity and poor defoliation after the application of harvest aids, chemical topping should not be performed too late(i.e., near the physiological cutout) by using MC at more than 180 g ha. The optimum timing of chemical topping probably varies from peak bloom to around seven days later, and the safest MC rates for chemical topping should be less than 180 g ha.展开更多
Larch caterpillars are widely distributed in the Great Xing’an boreal forests;however,the relationship between caterpillar defoliation dynamics and climatic factors is poorly understood.The aims of this study are to ...Larch caterpillars are widely distributed in the Great Xing’an boreal forests;however,the relationship between caterpillar defoliation dynamics and climatic factors is poorly understood.The aims of this study are to investigate the primary weather conditions that might influence forest defoliation and to identify the most important life stage of the larch caterpillar at which forest defoliation might be mitigated by incorporating more inhibitory influences from climatic factors.The life cycle of the larch caterpillar was partitioned into four stages and multiple linear regression and mixed effect models were combined with a relative weight analysis approach to evaluate the importance and influence of meteorological variables on defoliation dynamics.The results show that warmer temperatures in growing seasons and overwintering periods can increase the defoliation area,while rainy and humid growing seasons decrease the defoliation area.Total precipitation during the early instar larval period had the greatest power to explain the variance in defoliation dynamics and had a very strong inhibitory effect,followed by the accumulative temperatures of the late instar larval period which had a positive impact,and precipitation during the middle instar larval period which had a negative impact.Weather conditions during the early instar larval period had the greatest influence on the area defoliated and accounted for 40%of the explained variance.This study demonstrates that climatic warming and drying will increase the risk of larch caterpillar outbreaks in the Great Xing’an Mountains.展开更多
Remote sensing(RS) technologies provide robust techniques for quantifying net primary productivity(NPP) which is a key component of ecosystem production management. Applying RS, the confounding effects of carbon consu...Remote sensing(RS) technologies provide robust techniques for quantifying net primary productivity(NPP) which is a key component of ecosystem production management. Applying RS, the confounding effects of carbon consumed by livestock grazing were neglected by previous studies, which created uncertainties and underestimation of NPP for the grazed lands. The grasslands in Xinjiang were selected as a case study to improve the RS based NPP estimation. A defoliation formulation model(DFM) based on RS is developed to evaluate the extent of underestimated NPP between 1982 and 2011. The estimates were then used to examine the spatiotemporal patterns of the calculated NPP. Results show that average annual underestimated NPP was 55.74 gC·m^(-2)yr^(-1) over the time period understudied, accounting for 29.06% of the total NPP for the Xinjiang grasslands. The spatial distribution of underestimated NPP is related to both grazing intensity and time. Data for the Xinjiang grasslands show that the average annual NPP was 179.41 gC·m^(-2)yr^(-1), the annual NPP with an increasing trend was observed at a rate of 1.04 gC·m^(-2)yr^(-1) between 1982 and 2011. The spatial distribution of NPP reveals distinct variations from high to low encompassing the geolocations of the Tianshan Mountains, northern and southern Xinjiang Province and corresponding with mid-mountain meadow, typical grassland, desert grassland, alpine meadow, and saline meadow grassland types. This study contributes to improving RS-based NPP estimations for grazed land and provides a more accurate data to support the scientific management of fragile grassland ecosystems in Xinjiang.展开更多
The leaf phenology of trees has received particular attention for its crucial role in the global water and carbon balances,ecosystem,and species distribution.However,current studies on leaf phenology have mainly focus...The leaf phenology of trees has received particular attention for its crucial role in the global water and carbon balances,ecosystem,and species distribution.However,current studies on leaf phenology have mainly focused on temperate trees,while few studies including tropical trees.Little attention has been paid to globally extensive industrial plantations.Rubber plantations are important to both the local and global economies.In this study,we investigated the legacy effects of defoliation phenology on the following year’s leaf flushing,leaf disease,and also latex yield of rubber trees,an economically important tree to local people and the world.Results show that extended duration of defoliation increased the subsequent duration of refoliation and rates of infection by powdery mildew disease,but led to reduced latex yield in March.This legacy effect of rubber defoliation may relate to the carbohydrate reserved in the trees.A longer duration of defoliation would consume more reserved carbohydrates,reducing available reserves for disease defense and latex production.Extended duration of defoliation period was associated with either a lower temperature before the cessation of latex tapping in October-November and/or a higher temperature after the cessation of latex tapping in December-January.Leaf falling signals the end of photosynthetic activities in deciduous trees.Thus,the leaf falling phenology will impact ecological processes involving rubber trees.Our findings indicated that the inclusion of defoliation periods in future rubber trees’ research,will be crucial to furthering our understanding of leaf flushing,powdery mildew disease,and latex yield.展开更多
Early defoliation,which usually occurs during summer in pear trees,is gradually becoming a major problem that poses a serious threat to the pear industry in southern China.However,there is no system for evaluating the...Early defoliation,which usually occurs during summer in pear trees,is gradually becoming a major problem that poses a serious threat to the pear industry in southern China.However,there is no system for evaluating the responses of different cultivars to early defoliation,and our knowledge of the potential molecular regulation of the genes underlying this phenomenon is still limited.In this study,we conducted field investigations of 155 pear accessions to assess their resistance or susceptibility to early defoliation.A total of 126 accessions were found to be susceptible to early defoliation,and only 29 accessions were resistant.Among them,19 resistant accessions belong to the sand pear species(Pyrus pyrifolia).To identify the resistance genes related to early defoliation,the healthy and diseased samples of two sand pear accessions,namely,the resistant early defoliation accession‘Whasan’and the susceptible early defoliation accession‘Cuiguan’,were used to perform RNA sequencing.Compared with‘Cuiguan’,a total of 444 genes were uniquely differentially expressed in‘Whasan’.Combined with GO and KEGG enrichment analyses,we found that early defoliation was closely related to the stress response.Furthermore,a weighted gene co-expression network analysis revealed a high correlation of WRKY and ethylene responsive factor(ERF)transcription factors with early defoliation resistance.This study provides useful resistant germplasm resources and new insights into potentially essential genes that respond to early defoliation in pears,which may facilitate a better understanding of the resistance mechanism and molecular breeding of resistant pear cultivars.展开更多
Spruce budworm (SBW) outbreaks are one of the most devastating natural disturbances in spruce-balsam fir forests of eastern North America. Both early intervention strategy (EIS) and foliage protection strategy (FP) ar...Spruce budworm (SBW) outbreaks are one of the most devastating natural disturbances in spruce-balsam fir forests of eastern North America. Both early intervention strategy (EIS) and foliage protection strategy (FP) are being tested to limit forest losses, but the quantitative impact on forest carbon (C) dynamics is still unclear. In this study, we designed 19 separate scenarios of no intervention or varying success of EIS, FP, and their combination on SBW caused defoliation and mortality. We then used the TRIPLEX-Insect model to quantify their effects on forest C dynamics in the forests of the four provinces of Atlantic Canada. A scenario applying FP to 10%of the area with the greatest potential C losses of living biomass, protecting foliage in 10%of the forests is more realistic than higher proportion of FP given the high cost and large areas involved, resulted in reducing average cumulative net ecosystem productivity (NEP) from 2020 to 2039 by 56%–127%compared to a no outbreak scenario.Our results showed that FP would have to be applied everywhere to reduce tree mortality and increase NEP more than 8 years of successful EIS applied. However, if EIS can be successfully implemented for 12 years, it will maintain more forest C than FP applied everywhere during a moderate outbreak. We also found that the combination of EIS followed by FP in 10%of the areas disturbed by the SBW could maintain average cumulative NEP at similar levels to no defoliation in every province of Atlantic Canada. Black/red spruce forests younger than 60years old underwent the smallest changes in C dynamics whether using EIS, FP, or both. This highlights the importance of forest species, forest age, and their interactions on the effectiveness of a treatment during SBW outbreak. Overall, 31%–76%of the study area in Atlantic Canada could convert from a C sink to a source by 2039,if no protective measures are used under the worst-case scenarios, thus contributing to future climate warming.展开更多
Picea mongolica W. D. Xu. is an endemic species in China. The spruce forest is only found in semi-arid habitat in Inner Mongolia Autonomous Region of China. Based on the simulative defoliation experiment, it was prove...Picea mongolica W. D. Xu. is an endemic species in China. The spruce forest is only found in semi-arid habitat in Inner Mongolia Autonomous Region of China. Based on the simulative defoliation experiment, it was proved that Picea mongolica seedlings had the compensatory and overcompensatory effects under the certain defoliation rate. The results of variance analysis on growth indexes showed that in PM Ⅰ(natural regeneration seedlings under Picea mongolica forest), the differences of H 1(height in June 23) and H 2(height in September 3) were extremely significant, and the difference of D(diameter at the breast height) were not significant. In PM Ⅱ(artificial regeneration seedlings under Betula platyphylla Suk. forest), the difference of H 1 was significant, the difference of H 2 was not significant, and the difference of D was extremely significant. The regression equations were established and the compensatory and overcompensatory points were obtained. In PM Ⅰ, the compensatory points of H 1, H 2, and D were 0.7628, 0.7436, 0.5725, and the overcompensatory points were 0.6056, 0.5802 and 0.2909 respectively. In PM Ⅱ, the compensatory points of H 1, H 2, and D are 0.5012, 0.3421, 0.2488, and the overcompensatory points are 0.4137, 0.2633 and 0.0747 respectively. These results suggested that the induction of compensatory growth mechanisms in spruce seedlings required a threshold level of defoliation, and the insects in Picea mongolica forest could be controlled in a certain degree.展开更多
文摘Machine picking in cotton is an emerging practice in India,to solve the problems of labour shortages and production costs increasing.Cotton production has been declining in recent years;however,the high density planting system(HDPS)offers a viable method to enhance productivity by increasing plant populations per unit area,optimizing resource utilization,and facilitating machine picking.Cotton is an indeterminate plant that produce excessive vegeta-tive growth in favorable soil fertility and moisture conditions,which posing challenges for efficient machine picking.To address this issue,the application of plant growth retardants(PGRs)is essential for controlling canopy architecture.PGRs reduce internode elongation,promote regulated branching,and increase plant compactness,making cotton plants better suited for machine picking.PGRs application also optimizes photosynthates distribution between veg-etative and reproductive growth,resulting in higher yields and improved fibre quality.The integration of HDPS and PGRs applications results in an optimal plant architecture for improving machine picking efficiency.However,the success of this integration is determined by some factors,including cotton variety,environmental conditions,and geographical variations.These approaches not only address yield stagnation and labour shortages but also help to establish more effective and sustainable cotton farming practices,resulting in higher cotton productivity.
基金funded by the China Agriculture Research System(CARS–15–16)。
文摘Background Thidiazuron(TDZ)is a widely used chemical defoliant in commercial cotton production and is often combined with the herbicide Diuron to form the commercial defoliant mixture known as TDZ·Diuron(T·D,540 g·L^(-1)suspension).However,due to increasing concerns about the environmental and biological risks posed by Diuron,there is an urgent need to develop safer and more effective alternatives.Jasmonic acid(JA)and its derivatives are key phytohormones in organ senescence and abscission.Results Greenhouse experiments at the seedling stage revealed that Me-JA(0.8 mmol·L^(-1))alone did not induce defoliation.However,its co-application with TDZ(0.45 mmol·L^(-1))at concentrations of 0.6,0.8,and 1.0 mmol·L^(-1)significantly enhanced defoliation efficacy.The most effective combination—TDZ with 0.8 mmol·L^(-1)Me-JA—achieved a 100%defoliation rate at 5 days after treatment(DAT),23.7 percentage points higher than TDZ alone,and comparable to the commercial TDZ·Diuron formulation with equivalent TDZ content.Field trials conducted in Beijing(Shangzhuang),Hebei(Hejian),and Xinjiang(Shihezi)confirmed that the combination of 0.6 mmol·L^(-1)Me-JA with 1.70 mmol·L^(-1)TDZ provided optimal defoliation performance.At 21 DAT,the defoliation rate increased by 13.5–16.3 percentage points compared with TDZ alone.Furthermore,boll opening rates improved by 5.7–12.7 percentage points relative to TDZ-only treatments.Phytohormonal analyses from the Shangzhuang site showed that the combined treatment significantly altered hormone levels in both leaves and petioles.Compared with TDZ alone,the mixture reduced concentrations of auxin(IAA),cytokinins(Z+ZR,iP+iPA,DHZ+DHZR),and gibberellic acid(GA3),while increasing levels of JA,abscisic acid(ABA),and brassinosteroids(BR).These hormonal shifts may underlie the enhanced defoliation observed with the combined treatment.Importantly,the TDZ-Me-JA combination did not adversely affect cotton yield,yield components,or fiber quality.Conclusion The combination of Me-JA and TDZ has a good defoliation effect without affecting crop yield or fiber quality.And it provides a promising foundation for the development of novel,environmentally friendly cotton defoliants.
基金supported by the Ministry of Science,Technological Development and Innovation(Contract No.451-03-66/2024-03/200027)the Ministry of Agriculture,Forestry,and Water Management of the Republic of Serbia’s Forest Directorate within the project“Monitoring and Assessment of Air Pollution Impacts and its Effects on Forest Ecosystems in Republic of Serbia-Forest Condition Monitoring”.
文摘Forest ecosystems within national parks are threatened by various biotic and abiotic factors.To deter-mine the causes of the desiccation and death of trees in mixed coniferous and deciduous forests of Tara National Park(TNP),Serbia,we monitored defoliation and mortality of individual trees in permanent experimental plots.Data on the desiccation of a large number of trees were gathered by determining the total volume of dry trees and areas of forests under drying stress.The two sets of data were combined to determine the impact of climatic events,primarily drought periods,on the desiccation of forests.Combining data from the International Co-operative Program on Assessment and Monitoring of Air Pollution Effects on Forests(ICP Forests)with TNP data helped relate forest desiccation to climate events.Key climate signals were identified by monitoring tree defoliation changes in two permanent experimental plots,and then assessed for their influence on tree desicca-tion in the entire national park.The standardized precipita-tion evapotranspiration index(SPEI)was used for a more detailed analysis of the drought period.Despite the lack of climate data for a certain period,the SPEI index revealed a link between climate variables and the defoliation and desic-cation of forests.Furthermore,the desiccation of trees was preceded by a long drought period.Although mixed conifer-ous-deciduous forests are often considered less vulnerable to natural influences,this study suggests that forest ecosystems can become vulnerable regardless of tree species composi-tion due to multi-year droughts.These findings contribute to a better understanding of important clues for predicting pos-sible future desiccation of forests.Continuous monitoring of the state of forests and of more permanent experimental plots in national parks could provide better quality data and timely responses to stressful situations.
基金funded by the Talents ans its Youth Project of Xinjiang Production and Construction Corps(38000020924,380000358).
文摘Leaves are important‘source’organs that synthesize organic matter,providing carbon sources for plant growth.Here,we used Populus talassica×Populus euphratica,the dominant species in ecological and timber forests,to simulate carbon limitation through artificial 25%,50%,and 75%defoliation treatments and explore the effects on root,stem,and leaf morphology,biomass accumulation,and carbon allocation strategies.At the 60th d after treat-ment,under 25%defoliation treatment,the plant height,specific leaf weight,root surface area and volume,and concentrations of non-structural carbohydrates in stem and root were significantly increased by 9.13%,20.00%,16.60%,31.95%,5.12%,and 9.34%,respectively,relative to the control.There was no significant change in the growth indicators under 50%defoliation treatment,but the concentrations of non-structural carbohydrates in the leaf and stem significantly decreased,showing mostly a negative correlation between them.The opposite was observed in the root.Under 75%defoliation treatment,the plant height,ground diameter,leaf number,single leaf area,root,stem,and total biomass were significantly reduced by 14.15%,10.24%,14.86%,11.31%,11.56%,21.87%,and 16.82%,respectively,relative to the control.The concentrations of non-structural carbohydrates in various organs were significantly reduced,particularly in the consumption of the starch concentrations in the stem and root.These results indicated that carbon allocation strategies can be adjusted to increase the con-centration of non-structural carbohydrates in root and meet plant growth needs under 25%and 50%defoliation.However,75%defoliation significantly limited the distribution of non-structural carbohydrates to roots and stems,reduced carbon storage,and thus inhibited plant growth.Defoliation-induced carbon limitation altered the carbon allocation pattern of P.talassica×P.euphratica,and the relationship between carbon reserves in roots and tree growth recovery after defoliation was greater.This study provides a theoretical basis for the comprehen-sive management of P.talassica×P.euphratica plantations,as well as a reference for the study of plantation car-bon allocation strategies in the desert and semi-desert regions of Xinjiang under carbon-limitation conditions.
基金supported by the Croatian Science Foundation(project number IP-2018-01-8820)the Slovenian Research Agency core funding(grant number P4-0059).
文摘Ice storms can cause substantial damage to tree crowns and lead to growth reduction.However,in uneven-aged stands,the growth of an individual tree may also increase due to crown release caused by the damage or mortality of neighboring trees.Three years after the devastating ice storm in 2014 in mixed uneven-aged Dinaric forests(Croatia),we cored 156 European beech(Fagus sylvatica)and 85 silver fir(Abies alba)trees across 20 permanent sample plots to study the post-storm growth response as a function of tree,stand,site,spatial arrangement and local competition factors.The ice storm damaged over 84% of trees on the sampled plots.Among the cored trees,52.7% exhibited growth reduction,which on average amounted to3.1%relative to the pre-disturbance average.Trees with less than 40% crown damage maintained their pre-disturbance growth rates or experienced only minor growth suppression.While 60% of beech trees suffered a growth reduction at an average rate of 7.2%,the average radial increment of fir after the storm was 14.0% higher compared to the pre-storm rate.A linear mixedeffects model suggests that the growth response can largely be explained by the focal and neighboring tree species identity,tree competition pressure,focal and neighboring tree damage,crown size,slenderness index and stoniness.Growth release was positively associated with fir,inverse distance-weighted crown damage of the nearest neighbor,shorter crowns,slenderness,less stony sites and less damaged trees.The analysis suggests that at the same level of local competition load,trees with a broadleaved and damaged nearest neighbor are more likely to experience growth release than those with a coniferous or undamaged nearest neighbor.This implies that unevenaged stands with a substantial presence and mingling of both conifers and broadleaves are expected to be more resilient to ice storms and are less likely to suffer growth reduction.
文摘Modern agronomic concepts such as high-density planting systems are emerging in cotton-based cropping systems. Agronomic practices specific to new cotton varieties made in specific niches, management of the vegetation cover using growth regulators (retardants and defoliants) for better quality and above all the improvement of crop health through integrated nutrient management with an emphasis on the foliar feeding pattern, can significantly increase cotton productivity and improve the socio-economic status of farmers of cotton. It is in this context that studies on cotton sowing densities, the supplementation of mineral fertilization with trace elements and the management of the resumption of vegetation of cotton plants at the end of the cycle have been carried out in a farming environment and in research stations. The results of the survey in the farmer’s environment, of the trials conducted in stations and on observation posts showed a positive correlation between sowing densities and seed cotton yield. About 22% of the variations in seed cotton yield are related to sowing density. The best seed cotton yields are obtained with the high sowing densities in the north and the low densities in the south of the Ivorian cotton basin. Studies on the supplementation of base fertilizer with trace elements have shown that the combined application of 200 kg/ha of NPK + 50 kg/ha of urea + 2 kg/ha of ZnS04 increases the seed cotton yield and provides a monetary gain of 36,622 CFA francs/ha. The study on the management of vegetation resumption at the end of the cycle showed that the application of 4 l/ha of Ethephon and 62.5 ml/ha of Diuron at 100 days after emergence improves defoliation and capsule opening for better management of vegetation recovery at the end of the season. Studies have shown that seeding density is a factor in seed cotton yield. Seed cotton yields were improved by supplementing with mineral fertilizer with zinc and adding desiccants and defoliants at the end of the cycle.
基金Supported by Comprehensive Test Station in West Sichuan Plateau for National Apple's Industrial Technology System ( CARS-28)~~
文摘[ Objective ] The research aimed to discuss the occurrence regularity of apple early defoliation disease and control effects of fungicides in west Sichuan plateau. [ Method ] Apple early defoliation disease in west Sichuan plateau was systematically investigated during 2009 and 2011, and the control effects of different fungicides during different spraying periods were studied. [ Result] The species of pathogen mainly was Marssonina ma/i （ P. Henn）, accounting for 32.5%, Phyl-losticta Pirina Sa accounted for 29.9%, and Alternaria mali Roberts accounted for 25.7%. The field fluctuation regularity was as follows ： the disease generally be- gan in the mid-May and ended in early and middle October with only one damage peak during the whole year, the fluctuation had positive correlation with rainfall （ R2 =0.891 8 ＊ ＊ ）. Control test showed that 40% flusilazole had the best control effect （86.5%）, which was best to apply after anthesis. [ Conclusion ] The paper provided theoretical basis for the effective control against apple early defoliation disease.
文摘[Objective] It aimed to find an optimum condition for compensatory growth of peony.[Method] The different defoliation intensies and frequencies of penoy were implemented to observe accumulated aboveground biomass, regenerated bud number,stem-leaf ratio and the chlorophyll concentration change in residual leaves.[Result] When the defoliation frequency was conducted every 20 d once and defoliaton intensity was from 40%-60%,the accumulated biomass was biggest, when the defoliation frequency was conducted every 10 d once and defoliation intensity was from 60%-80% the regenerated bud number was maximum.The stem-leaf ratio of mild and moderate defoliation intensities(20%-60%) was significantly lower than that of control group.When the defoliation frequency was conducted every 20 d once and defoliation intensity was from 40%-60%,the chlorophyll concentration in residual leaves was obviously higher than that of control group.[Conclusion] The proper defoliation intensity(60%) and lower defoliation frequency(defoliation was conducted every 20 d once) were most favorable to the growth and regenerated of peony which was the compensatory growth.
基金Supported by the Vice-Prosidency for Research of theUniversity of Cartagena for the financial aid through the Program to Support Research Groups (2012-2013)K.Caballero is sponsored by the National Program for Doctoral Formation Colciencias,567-2012
文摘Objective:To determine the biological effects of essential oils(EOs) isolated from Cymbopogon iiardus,Cymbopogon Jlexuosus and Cvrnbopogon marlinii grown in Colombia against two Lepidoptera larvae,common pests in the oil palm.Methods:Specimens were captured in the field and the antifeedant activity and dermal contact lethality of EOs were measured against Acharia fusca and Euprosterna elaeasa(Lepidoptera:I.imacodidae) at various concentrations 0.002-0.600 μL/cm^3 and 0.002-8 μL/g,respectively.Results:All EOs exhibited strong antifeedant and toxicity activity toward Acharia fusca and Euprosterna elaeasa larvae.Cymbopogon marlinii oil was llie most active againsl both pest insect species,although all tested EOs were better than the synthetic;repellent IR535 on both insects.Conclusions:Colombian EOs have potential for integrated pest management programs in the oil palm industry.
基金supported by the National Natural Science Foundation of China(31560342)the Major Science and Technology Projects of Xinjiang Production and Construction Corps,China(2016AA001-2)the National Key Research and Development Program of China(2017YFD0201900)
文摘The aim of this study was to elucidate the effects of different machine-harvested cotton-planting patterns on defoliation,yield,and fiber quality in cotton and to provide support for improving the quality of machine-harvested cotton.In the 2015 and 2016 growing seasons,the Xinluzao 45(XLZ45)and Xinluzao 62(XLZ62)cultivars,which are primarily cultivated in northern Xinjiang,were used as study materials.Conventional wide-narrow row(WNR),wide and ultra-narrow row(UNR),wide-row spacing with high density(HWR),and wide-row spacing with low density(LWR)planting patterns were used to assess the effects of planting patterns on defoliation,yield,and fiber quality.Compared with WNR,the seed cotton yields were significantly decreased by 2.06–5.48%for UNR and by 2.50–6.99%for LWR,respectively.The main cause of reduced yield was a reduction in bolls per unit area.The variation in HWR yield was–1.07–1.07%with reduced bolls per unit area and increased boll weight,thus demonstrating stable production.In terms of fiber quality indicators,the planting patterns only showed significant effects on the micronaire value,with wide-row spacing patterns showing an increase in the micronaire values.The defoliation and boll-opening results showed that the number of leaves and dried leaves in HWR was the lowest among the four planting patterns.Prior to the application of defoliating agent and before machine-harvesting,the numbers of leaves per individual plant in HWR were decreased by 14.45 and 25.00%on average,respectively,compared with WNR,while the number of leaves per unit area was decreased by 27.44 and 36.21%on average,respectively.The rates of boll-opening and defoliation in HWR were the highest.Specifically,the boll-opening rate before defoliation and machine-harvesting in HWR was 44.54 and 5.94%higher on average than in WNR,while the defoliation rate prior to machine-harvesting was 3.45%higher on average than in WNR.The numbers of ineffective defoliated leaves and leaf trash in HWR were the lowest,decreased by 33.40 and 32.43%,respectively,compared with WNR.In conclusion,the HWR planting pattern is associated with a high and stable yield,does not affect fiber quality,promotes early maturation,and can effectively decrease the amount of leaf trash in machine-picked seed cotton,and thus its use is able to improve the quality of machine-harvested cotton.
基金supported by the National Natural Science Foundation of China(30825028)the Program of the National High-Tech R&D Program of China(2011AA10A206)the Innovation Fund for Graduate Student of China Agricultural University(KYCX2010032)
文摘Timing of harvest is critical for mechanical picking in cotton production, especially in those regions with double cropping system. Appropriate and safe harvest aids will improve timing and facilitate harvest of cotton in the double cropping system. Three defoliants （dimethipin, thidiazuron, and thidiazuron-diuron） and one boll opener （ethephon） were included in this research. They were evaluated for their effects on defoliation, boll opening, seedcotton yield, seed quality, and fiber quality of field grown cotton when used alone or as a mixture in 2009 and 2010. Defoliation and/or boll opening were increased by all three defoliants and ethephon, especially by mixtures of a defoliant and ethephon. First harvest of seedcotton was significantly increased with defoliant-ethephon mixtures. No significant adverse effects were observed on boll weight, lint percentage, seed quality, and fiber properties. It was estimated that tank mixes of ethephon and one of the three defoliants can improve the adjusted gross revenue. Boll opening can be used as an alternative indicator for the adjusted gross revenue, because, it was linearly and positively correlated with the relative adjusted gross revenue and convenient in measurements. Wheat seedling growth was not affected by thidiazuron, whereas its seedling emergence, root dry weight, relative water content, and electrolyte leakage were adversely affected by dimethipin and thidiazuron- diuron when concentration was above 340 and 100 g （a.i.） ha-1, respectively. 90% defoliation and 80% boll opening were observed with the high rate of thidiazuron-ethephon mixture, but no adverse effects on winter wheat. The results suggested that tank mixes of ethephon with thidiazuron can be used effectively and safely in the cotton-winter wheat double cropping system to improve yield without adverse effects on seed quality and fiber quality.
基金funded by the China Agriculture Research System (CAAS-04-PS08)the National Transgenic Project of China (2014ZX08004-005)the Agricultural Science and Technology Innovation Program of China
文摘Identifying a superior soybean variety with high defoliator resistance is important to avoid yield loss. Cotton bollworm(Helicoverpa armigera Hübner) is one of the major defoliators of soybean(Glycine max [L.] Merr.) worldwide. In this study, we evaluated the effect of H. armigera larvae on ED059, a wild soybean(Glycine soja Sieb. et Zucc.), and three cultivated soybean varieties: Tianlong 2, PI 535807, and PI 533604, in choice and no-choice assays. The percentage of ED059 leaflets consumed by H. armigera was lower than that of the three cultivated soybeans. Larvae that fed on ED059 exhibited low weight gain and high mortality rate.Waldbauer nutritional indices suggested that ED059 reduced the growth, consumption, and frass production of H. armigera larvae. Larvae that fed on ED059 showed lower efficiency of conversion of ingested and of digested food than those that fed on Tianlong 2 and PI 533604.However, they showed statistically similar consumption index and approximate digestibility compared with those fed on the three cultivated soybeans. Quantitative real-time PCR analysis revealed that 24 h after insect attack, ED059 had higher transcript levels of Kunitz trypsin inhibitor 3, Cysteine proteinase inhibitor 2, and Nerolidol synthase 1 but a lower transcript level of Pathogenesis-related protein 1 than Tianlong 2. The gene expression results were consistent with the presence of higher levels of jasmonic acid(JA) and transcript levels of the JA biosynthesis enzyme allene oxide cyclase 3 in ED059 than in Tianlong 2. Our findings indicate that ED059 is a superior soybean line with strong insect resistance that may be mediated via the JA pathway.
基金supported by the National Key Research and Development Program of China(2018YFD0100306)the National Natural Science Foundation of China(31301257)。
文摘Defoliation is an indispensable step in cotton production with mechanical harvesting,especially in the North China Plain(NCP)where mechanical harvesting is limited by a large proportion of green leaves and unopened bolls at harvest time due to insufficient thermal resources.It is essential to quantify the optimal use of defoliation products while minimizing yield and quality loss in China.The objective of this study was to test the effect of a new defoliant Xinsaili(XSL,a compound of 10% thidiazuron and 40% ethephon)on the spatial distribution of cotton leaves and bolls,yield and quality in the NCP.There were four treatments:XSL 1800 m L ha^(-1),XSL 2700 m L ha^(-1),XSL splitted into two equal applications(1350 m L ha^(-1) for each),and XSL-free(water)control.Field experiments were conducted in Hebei,China in 2016-2017.All the defoliant treatments did not significantly affect cotton yield and fiber quality compared with the water control.At harvest time,the rate of open bolls under XSL 2700 m L ha^(-1) was 13.5% higher than that under XSL-free control,while the other two treatments showed no significant difference,across the two years.Defoliation percentage of the three XSL treatments showed no difference,but they were on average 42.2% higher than that of XSL-free control.The year-round effect of the defoliant XSL was significant,indicating that climate factors would affect its application.It was concluded that the optimal dose of XSL in the NCP was 2700 m L ha^(-1),and it was unnecessary to split it into two applications.These results would promote cotton mechanical harvesting and reduce the labor cost of cotton production in China.
基金supported by the National Key Research and Development Program of China(2018YFD0100306)the China Agriculture Research System of MOF and MARA(CARS-15-16)。
文摘Early maturity, complete defoliation and boll opening are essential for the efficient machine harvesting of cotton. Chemical topping, involving one extra application of mepiquat chloride(MC) in addition to its traditional multipleapplication strategy, may be able to replace manual topping. However, it is not known whether this chemical topping technique will influence maturity or cotton responses to harvest aids. In this 2-yr field study, we determined the effects of the timing of chemical topping using various rates of MC on boll opening percentage(BOP) before application of harvest aids(50% thidiazuron··ethephon suspension concentrate, referred to as TE), and the defoliation percentage(DP) and BOP 14 days after TE application. The results indicated that late chemical topping(near the physiological cutout, when the nodes above white flower is equal to 5.0) significantly decreased BOP before TE by 5.9–11.2% compared with early(at peak bloom) or middle(seven days after peak bloom) treatments in 2019, which was a relatively normal year based on crop condition. Also, a high MC rate(270 g ha) showed a significantly lower(22.0%) BOP before TE than low(90 g ha) or medium(180 g ha) rates. In 2020, which was characterized by stronger vegetative growth in the late season, the late chemical topping reduced the number of leaves before TE application relative to early or middle treatments, but had lower DP(23.2–27.2%) 14 days after TE application. The high MC rate showed a leaf count before TE application that was similar to the low and medium rates, but it showed the most leaves after TE and much lower(15.0–21.7%) DP in 2020. These results suggest that late timing of chemical topping and a high MC rate decreased the sensitivity of leaves to harvest aids. Further analysis indicated that the late chemical topping mainly affected the leaf drop from the mainstem and fruiting branches where the late regrowth occurred, and the high MC rate reduced leaf shedding from these parts and also from the vegetative branches. In conclusion, chemical topping with MC during the bloom period affected cotton maturity and responses to harvest aids in different ways according to the crop condition. To avoid the risks of delayed maturity and poor defoliation after the application of harvest aids, chemical topping should not be performed too late(i.e., near the physiological cutout) by using MC at more than 180 g ha. The optimum timing of chemical topping probably varies from peak bloom to around seven days later, and the safest MC rates for chemical topping should be less than 180 g ha.
基金The work was supported by the National Key R&D Program of China(2017YFA0604403).
文摘Larch caterpillars are widely distributed in the Great Xing’an boreal forests;however,the relationship between caterpillar defoliation dynamics and climatic factors is poorly understood.The aims of this study are to investigate the primary weather conditions that might influence forest defoliation and to identify the most important life stage of the larch caterpillar at which forest defoliation might be mitigated by incorporating more inhibitory influences from climatic factors.The life cycle of the larch caterpillar was partitioned into four stages and multiple linear regression and mixed effect models were combined with a relative weight analysis approach to evaluate the importance and influence of meteorological variables on defoliation dynamics.The results show that warmer temperatures in growing seasons and overwintering periods can increase the defoliation area,while rainy and humid growing seasons decrease the defoliation area.Total precipitation during the early instar larval period had the greatest power to explain the variance in defoliation dynamics and had a very strong inhibitory effect,followed by the accumulative temperatures of the late instar larval period which had a positive impact,and precipitation during the middle instar larval period which had a negative impact.Weather conditions during the early instar larval period had the greatest influence on the area defoliated and accounted for 40%of the explained variance.This study demonstrates that climatic warming and drying will increase the risk of larch caterpillar outbreaks in the Great Xing’an Mountains.
基金supported by the international Partnership Program of the Chinese Academy of Science(Grant No.131965KYSB20160004)the National Natural Science Foundation of China(Grant No.U1803243)+1 种基金the Network Plan of the Science and Technology Service,Chinese Academy of Sciences(STS Plan)Qinghai innovation platform construction project(2017-ZJ-Y20)
文摘Remote sensing(RS) technologies provide robust techniques for quantifying net primary productivity(NPP) which is a key component of ecosystem production management. Applying RS, the confounding effects of carbon consumed by livestock grazing were neglected by previous studies, which created uncertainties and underestimation of NPP for the grazed lands. The grasslands in Xinjiang were selected as a case study to improve the RS based NPP estimation. A defoliation formulation model(DFM) based on RS is developed to evaluate the extent of underestimated NPP between 1982 and 2011. The estimates were then used to examine the spatiotemporal patterns of the calculated NPP. Results show that average annual underestimated NPP was 55.74 gC·m^(-2)yr^(-1) over the time period understudied, accounting for 29.06% of the total NPP for the Xinjiang grasslands. The spatial distribution of underestimated NPP is related to both grazing intensity and time. Data for the Xinjiang grasslands show that the average annual NPP was 179.41 gC·m^(-2)yr^(-1), the annual NPP with an increasing trend was observed at a rate of 1.04 gC·m^(-2)yr^(-1) between 1982 and 2011. The spatial distribution of NPP reveals distinct variations from high to low encompassing the geolocations of the Tianshan Mountains, northern and southern Xinjiang Province and corresponding with mid-mountain meadow, typical grassland, desert grassland, alpine meadow, and saline meadow grassland types. This study contributes to improving RS-based NPP estimations for grazed land and provides a more accurate data to support the scientific management of fragile grassland ecosystems in Xinjiang.
基金financially supported by the Key Research Program of Frontier Sciences,the Chinese Academy of Sciences (No.QYZDY-SSW-SMC014)the National Natural Science Foundation of China (No.32171576)。
文摘The leaf phenology of trees has received particular attention for its crucial role in the global water and carbon balances,ecosystem,and species distribution.However,current studies on leaf phenology have mainly focused on temperate trees,while few studies including tropical trees.Little attention has been paid to globally extensive industrial plantations.Rubber plantations are important to both the local and global economies.In this study,we investigated the legacy effects of defoliation phenology on the following year’s leaf flushing,leaf disease,and also latex yield of rubber trees,an economically important tree to local people and the world.Results show that extended duration of defoliation increased the subsequent duration of refoliation and rates of infection by powdery mildew disease,but led to reduced latex yield in March.This legacy effect of rubber defoliation may relate to the carbohydrate reserved in the trees.A longer duration of defoliation would consume more reserved carbohydrates,reducing available reserves for disease defense and latex production.Extended duration of defoliation period was associated with either a lower temperature before the cessation of latex tapping in October-November and/or a higher temperature after the cessation of latex tapping in December-January.Leaf falling signals the end of photosynthetic activities in deciduous trees.Thus,the leaf falling phenology will impact ecological processes involving rubber trees.Our findings indicated that the inclusion of defoliation periods in future rubber trees’ research,will be crucial to furthering our understanding of leaf flushing,powdery mildew disease,and latex yield.
基金supported by the earmarked fund for Jiangsu Agricultural Industry Technology System,China(JATS[2021]453)the National Key Research and Development Program of China(2021YFD1200200)the earmarked fund for China Agriculture Research System(CARS-28).
文摘Early defoliation,which usually occurs during summer in pear trees,is gradually becoming a major problem that poses a serious threat to the pear industry in southern China.However,there is no system for evaluating the responses of different cultivars to early defoliation,and our knowledge of the potential molecular regulation of the genes underlying this phenomenon is still limited.In this study,we conducted field investigations of 155 pear accessions to assess their resistance or susceptibility to early defoliation.A total of 126 accessions were found to be susceptible to early defoliation,and only 29 accessions were resistant.Among them,19 resistant accessions belong to the sand pear species(Pyrus pyrifolia).To identify the resistance genes related to early defoliation,the healthy and diseased samples of two sand pear accessions,namely,the resistant early defoliation accession‘Whasan’and the susceptible early defoliation accession‘Cuiguan’,were used to perform RNA sequencing.Compared with‘Cuiguan’,a total of 444 genes were uniquely differentially expressed in‘Whasan’.Combined with GO and KEGG enrichment analyses,we found that early defoliation was closely related to the stress response.Furthermore,a weighted gene co-expression network analysis revealed a high correlation of WRKY and ethylene responsive factor(ERF)transcription factors with early defoliation resistance.This study provides useful resistant germplasm resources and new insights into potentially essential genes that respond to early defoliation in pears,which may facilitate a better understanding of the resistance mechanism and molecular breeding of resistant pear cultivars.
基金part of an Early Intervention Strategy research project funded by Natural Resources Canada and the Healthy Forest Partnershipfinanced by the Fonds de Recherche du Québec (FQRNT) programNatural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant
文摘Spruce budworm (SBW) outbreaks are one of the most devastating natural disturbances in spruce-balsam fir forests of eastern North America. Both early intervention strategy (EIS) and foliage protection strategy (FP) are being tested to limit forest losses, but the quantitative impact on forest carbon (C) dynamics is still unclear. In this study, we designed 19 separate scenarios of no intervention or varying success of EIS, FP, and their combination on SBW caused defoliation and mortality. We then used the TRIPLEX-Insect model to quantify their effects on forest C dynamics in the forests of the four provinces of Atlantic Canada. A scenario applying FP to 10%of the area with the greatest potential C losses of living biomass, protecting foliage in 10%of the forests is more realistic than higher proportion of FP given the high cost and large areas involved, resulted in reducing average cumulative net ecosystem productivity (NEP) from 2020 to 2039 by 56%–127%compared to a no outbreak scenario.Our results showed that FP would have to be applied everywhere to reduce tree mortality and increase NEP more than 8 years of successful EIS applied. However, if EIS can be successfully implemented for 12 years, it will maintain more forest C than FP applied everywhere during a moderate outbreak. We also found that the combination of EIS followed by FP in 10%of the areas disturbed by the SBW could maintain average cumulative NEP at similar levels to no defoliation in every province of Atlantic Canada. Black/red spruce forests younger than 60years old underwent the smallest changes in C dynamics whether using EIS, FP, or both. This highlights the importance of forest species, forest age, and their interactions on the effectiveness of a treatment during SBW outbreak. Overall, 31%–76%of the study area in Atlantic Canada could convert from a C sink to a source by 2039,if no protective measures are used under the worst-case scenarios, thus contributing to future climate warming.
文摘Picea mongolica W. D. Xu. is an endemic species in China. The spruce forest is only found in semi-arid habitat in Inner Mongolia Autonomous Region of China. Based on the simulative defoliation experiment, it was proved that Picea mongolica seedlings had the compensatory and overcompensatory effects under the certain defoliation rate. The results of variance analysis on growth indexes showed that in PM Ⅰ(natural regeneration seedlings under Picea mongolica forest), the differences of H 1(height in June 23) and H 2(height in September 3) were extremely significant, and the difference of D(diameter at the breast height) were not significant. In PM Ⅱ(artificial regeneration seedlings under Betula platyphylla Suk. forest), the difference of H 1 was significant, the difference of H 2 was not significant, and the difference of D was extremely significant. The regression equations were established and the compensatory and overcompensatory points were obtained. In PM Ⅰ, the compensatory points of H 1, H 2, and D were 0.7628, 0.7436, 0.5725, and the overcompensatory points were 0.6056, 0.5802 and 0.2909 respectively. In PM Ⅱ, the compensatory points of H 1, H 2, and D are 0.5012, 0.3421, 0.2488, and the overcompensatory points are 0.4137, 0.2633 and 0.0747 respectively. These results suggested that the induction of compensatory growth mechanisms in spruce seedlings required a threshold level of defoliation, and the insects in Picea mongolica forest could be controlled in a certain degree.
