Rice is one of the most important cereal crops in the world, and a substantial increase in grain yield is necessary for food security. However, high yields of semidwarf modern rice varieties are heavily dependent on t...Rice is one of the most important cereal crops in the world, and a substantial increase in grain yield is necessary for food security. However, high yields of semidwarf modern rice varieties are heavily dependent on the application of mineral nitrogenous fertilizer (Tilman et al., 2002;Sun et al., 2014). Nitrogen (N)-insensitive sponses associated with reduced N-use efficiency (NUE) is a major characteristic of the green revolution varieties (GRVs), in which the growth-inhibiting protein SLENDER RICE1 (SLR1) accumulates (Li et al., 2018). Unfortunately, increasing the level of N fertilizer use to reach the full yield potential of GRVs is subject to diminishing returns, quite apart from its deleterious effect on the environments (Rahn et al., 2009;Liu et al., 2015). Therefore, there is an urgent need to develop new rice GRVs that increase NUE while maintaining their high yields. Recently, several genes (e.g., DEP1, OsNRTl.lB, OsNRT2.3b, ARE1 and GRF4) responsible for improved NUE have been identified in rice (Sun et al.. 2014;Hu et al., 2015;Fan et al., 2016;Wang et al., 2018;Li et al., 2018). More importantly, boosting the activity of the transcription factor GRF4 overcomes the ability of SLR1 to prevent the GRF4-GIF1 interaction, which in turn promotes the coordinated expression of the genes involved in N assimilation and carbon fixation and consequently enhances the NUE of rice GRVs, thereby improving our ability to grow crops sustainably (Li et al., 2018). However, current understanding of the genetic basis for improving NUE remains at the level of identification of a number of quantitative trait loci (QTLs), without any understanding of the nature of the gene products.展开更多
Selection of tree species with a high capacity to assimilate N and efficiently utilize N resources would facilitate the success of initial tree seedling establishment in infertile soils.The preference for N forms was ...Selection of tree species with a high capacity to assimilate N and efficiently utilize N resources would facilitate the success of initial tree seedling establishment in infertile soils.The preference for N forms was tested using three pine species(Pinus densata,Pinus tabuliformis and Pinus yunnanensis).Pinus densata is a natural diploid hybrid between P.tabuliformis and P.yunnanensis.Methods Seedlings of three pine species were supplied with nitrate-N,ammonium-N(at two different pH regimes)or combined ammonium and nitrate as a nitrogen source in perlite culture in a controlled environment.Important Findings Seedlings of P.densata had higher total biomass and net photosynthesis when supplied with nitrate-N and ammonium nitrate than with ammonium-N.In parental species,total biomass and net photosynthesis for P.yunnanensis seedlings was higher in ammonium-N than in nitrate-N,whereas the other parental species P.tabuliformis had the highest total biomass among species for all treatments except ammonium with CaCO_(3).Most morphological traits in P.densata seedlings were intermediate between its two parental species.However,N-use efficiency and photosynthetic N-use efficiency of P.densata significantly exceeded both parents when supplied with nitrate-N and ammonium nitrate.The results suggested that the diploid hybrid tree species P.densata has a preference for nitrate and is not well adapted to ammonium-N as a sole nitrogen source regardless of the growth medium pH.Based on changes in environmental conditions,such as predicted future temperature increases in high altitude areas associated with climate change,P.densata is likely to be increasingly competitive and have wide adaptation in high altitude regions.展开更多
Understanding the interactions between salinity and fertilizers is of significant importance for enhancing crop yield and fertilizeruse efficiency. In this study a complete block design experiment was performed in the...Understanding the interactions between salinity and fertilizers is of significant importance for enhancing crop yield and fertilizeruse efficiency. In this study a complete block design experiment was performed in the Hetao Irrigation District of Inner Mongolia,China, to evaluate the effects of interactions between soil salinity and nitrogen(N) application rate on sunflower photosynthesis and growth and to determine the optimum N application rate for sunflower growth in the district. Four levels of soil salinity expressed as electrical conductivity(0.33–0.60, 0.60–1.22, 1.2–2.44, and 2.44–3.95 dS m-1) and three application rates of N fertilization(90, 135,and 180 kg ha-1) were applied to 36 micro-plots. Soil salinity inhibited the photosynthetic rate, stomatal conductance, transpiration rate, plant height, leaf area, and aboveground dry matter of sunflowers. The intercellular CO2 concentration first decreased and then increased with increasing soil salinity in the seedling stage, and the instantaneous leaf water-use efficiency fluctuated with soil salinity. The stomatal and non-stomatal limitations of sunflowers alternated in the seedling stage; however, in the bud, blooming,and mature stages, the stomatal limitation was prevalent when the salinity level was lower than 2.44 dS m-1, whereas the nonstomatal limitation was predominant above the salinity level. The application of N fertilizer alleviated the adverse effects of salinity on sunflower photosynthesis and growth to some extent. During some key growth periods, such as the seedling and bud stages, a moderate N application rate(135 kg ha-1) resulted in the maximum photosynthetic rate and yielded the maximum dry matter. We suggest a moderate N application rate(135 kg ha-1) for the Hetao Irrigation District and other sunflower-growing areas with similar ecological conditions.展开更多
The need to maintain high rice yields and improve fertilizer nitrogen(N)-use efficiency has fueled the use of tools such as leaf colour chart(LCC) and chlorophyll meter(SPAD meter) in managing fertilizer N based on co...The need to maintain high rice yields and improve fertilizer nitrogen(N)-use efficiency has fueled the use of tools such as leaf colour chart(LCC) and chlorophyll meter(SPAD meter) in managing fertilizer N based on colour of the leaf. Field experiments were conducted during 2011 to 2013 at Ludhiana, India to assess the need for basal N application and to establish critical threshold values of leaf greenness as measured by LCC and SPAD meter for formulating strategies for in-season management of fertilizer N in dry direct-seeded rice(DDSR). Avoiding application of N at sowing did not adversely affect rice grain yield, indicating that basal N application in DDSR was not necessary and might lead to reduced N-use efficiency. Monitoring N uptake rate during the growing season of DDSR suggested that N uptake rate peaked at the two growth stages: maximum tillering(42 to 56 days after sowing(DAS))and panicle initiation stages(70 to 84 DAS). Using the Cate-Nelson procedure, critical LCC and SPAD meter values for fertilizer N application worked out to be 4 and 37, respectively. Real-time fertilizer N management strategy based on applying 30 kg N ha-1whenever SPAD meter or LCC readings fell below the critical values maintained optimum rice yields along with higher N-use efficiency than that observed by following blanket recommendation for fertilizer N in the region. The fixed-time variable-dose strategy consisted of applying prescriptive doses of 20 kg N ha-1at 14 DAS and 30 kg N ha-1at 28 DAS and corrective doses of 30, 40 or 50 kg N ha-1at 49 and 70 DAS depending upon LCC shade to be ≥ 4, 4–3.5, or < 3.5 and SPAD meter readings to be ≥ 40, 40–35, or< 35, respectively. This strategy also resulted in optimal rice yield along with higher N-use efficiency as compared to the blanket recommendation. This study revealed that in DDSR, fertilizer N could be managed more efficiently using the tools of LCC and SPAD meter than the current blanket recommendation.展开更多
Zero-tillage has become increasingly attractive in rice production in China.This study was conducted to determine the feasibility of two possible improved N management practices with fewer N applications in zero-tilla...Zero-tillage has become increasingly attractive in rice production in China.This study was conducted to determine the feasibility of two possible improved N management practices with fewer N applications in zero-tillage rice:(1)two split applications of urea at75 kg N ha^(-1)at mid-tillering and 45 kg N ha^(-1)at panicle initiation(U_(120–2)),and(2)a single application of cross-linked polyacrylamide-coated urea(a slow-release fertilizer)at midtillering at a rate of 150 kg N ha^(-1)(PCU_(150–1)).Three field experiments were conducted to compare grain yield and N-use efficiency among several N treatments:a zero-N control(CK),U_(120–2),PCU_(150–1),a single application of urea at mid-tillering at a rate of 150 kg N ha^(-1)(U_(150–1)),and a commonly recommended N management practice for conventional tillage rice(three split applications of urea with 75 kg N ha^(-1)as basal,30 kg N ha^(-1)at mid-tillering,and 45 kg N ha^(-1)at panicle initiation)(U_(150–3)).Treatments with N application(U_(120–2),PCU_(150–1),U_(150–1),and U_(150–3))produced 1.08–3.16 t ha^(-1)higher grain yields than CK.Grain yields under both U_(120–2)and PCU_(150–1)were comparable to that in U_(150–3).Recovery efficiency of N(RE_N),agronomic N-use efficiency(AE_N)and partial factor productivity of applied N(PFP_N)were increased under U_(120–2)and were similar under PCU_(150–1)to those under U_(150–3).U_(150–1)showed lower grain yield,RE_N,AE_N,and PFP_Nthan U_(150–3).These results suggest that U_(150–3)can be replaced with U_(120–2)to achieve both an increase in N-use efficiency and a reduction in number of N applications and or by PCU_(150–1)to achieve a maximum reduction in number of N applications in zero-tillage rice production in China.展开更多
More intense, more frequent, and longer heat-waves are expected in the future due to global warming, which could have dramatic ecological impacts. Increasing nitrogen （N） availability and its dynamics will likely im...More intense, more frequent, and longer heat-waves are expected in the future due to global warming, which could have dramatic ecological impacts. Increasing nitrogen （N） availability and its dynamics will likely impact plant responses to heat stress and carbon （C） sequestration in terrestrial ecosystems. This field study examined the effects of N availability on plant response to heat-stress （HS） treatment in naturally-occurring vegetation. HS （5 d at ambient or 40.5 ℃） and N treatments （±N） were applied to 16 1 m^2 plots in restored prairie vegetation dominated by Andropogon gerardii （warm-season C4 grass） and Solidago canadensis （warm-season C3 forb）. Before, during, and after HS, air, canopy, and soil temperature were monitored; net CO2 assimilation （Pn）, quantum yield of photosystem Ⅱ （ФpsⅡ）, stomatal conductance （gs）, and leaf water potential （ψw） of the dominant species and soil respiration （Rsoll） of each plot were measured daily during HS. One week after HS, plots were harvested, and C% and N% were determined for rhizosphere and bulk soil, and above-ground tissue （green/senescent leaf, stem, and flower）. Photosynthetic N-use efficiency （PNUE） and N resorption rate （NRR） were calculated. HS decreased Pn, gs, ψw, and PNUE for both species, and ＋N treatment generally increased these variables （±HS）, but often slowed their post-HS recovery. Aboveground biomass tended to decrease with HS in both species （and for green leaf mass in S. canadensis）, but decrease with ＋N for A. gerardii and increase with ＋N for S. canadensis. For A. gerardii, HS tended to decrease N% in green tissues with ＋N, whereas in S. canadensis, HS increased N% in green leaves. Added N decreased NRR for A. gerardii and HS increased NRR for S. canadensis. These results suggest that heat waves, though transient, could have significant effects on plants, communities, and ecosystem N cycling, and N can influence the effect of heat waves.展开更多
基金supported by grants from the National Natural Science Foundation of China (31830082)the National Key Research and Development Program of China (2016YFD0100401)the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB27010000)
文摘Rice is one of the most important cereal crops in the world, and a substantial increase in grain yield is necessary for food security. However, high yields of semidwarf modern rice varieties are heavily dependent on the application of mineral nitrogenous fertilizer (Tilman et al., 2002;Sun et al., 2014). Nitrogen (N)-insensitive sponses associated with reduced N-use efficiency (NUE) is a major characteristic of the green revolution varieties (GRVs), in which the growth-inhibiting protein SLENDER RICE1 (SLR1) accumulates (Li et al., 2018). Unfortunately, increasing the level of N fertilizer use to reach the full yield potential of GRVs is subject to diminishing returns, quite apart from its deleterious effect on the environments (Rahn et al., 2009;Liu et al., 2015). Therefore, there is an urgent need to develop new rice GRVs that increase NUE while maintaining their high yields. Recently, several genes (e.g., DEP1, OsNRTl.lB, OsNRT2.3b, ARE1 and GRF4) responsible for improved NUE have been identified in rice (Sun et al.. 2014;Hu et al., 2015;Fan et al., 2016;Wang et al., 2018;Li et al., 2018). More importantly, boosting the activity of the transcription factor GRF4 overcomes the ability of SLR1 to prevent the GRF4-GIF1 interaction, which in turn promotes the coordinated expression of the genes involved in N assimilation and carbon fixation and consequently enhances the NUE of rice GRVs, thereby improving our ability to grow crops sustainably (Li et al., 2018). However, current understanding of the genetic basis for improving NUE remains at the level of identification of a number of quantitative trait loci (QTLs), without any understanding of the nature of the gene products.
基金This study has been supported by National Natural Science Foundation of China(grant no:30671666)University Key Teacher funds from the Ministry of Education,People’s Republic of China.
文摘Selection of tree species with a high capacity to assimilate N and efficiently utilize N resources would facilitate the success of initial tree seedling establishment in infertile soils.The preference for N forms was tested using three pine species(Pinus densata,Pinus tabuliformis and Pinus yunnanensis).Pinus densata is a natural diploid hybrid between P.tabuliformis and P.yunnanensis.Methods Seedlings of three pine species were supplied with nitrate-N,ammonium-N(at two different pH regimes)or combined ammonium and nitrate as a nitrogen source in perlite culture in a controlled environment.Important Findings Seedlings of P.densata had higher total biomass and net photosynthesis when supplied with nitrate-N and ammonium nitrate than with ammonium-N.In parental species,total biomass and net photosynthesis for P.yunnanensis seedlings was higher in ammonium-N than in nitrate-N,whereas the other parental species P.tabuliformis had the highest total biomass among species for all treatments except ammonium with CaCO_(3).Most morphological traits in P.densata seedlings were intermediate between its two parental species.However,N-use efficiency and photosynthetic N-use efficiency of P.densata significantly exceeded both parents when supplied with nitrate-N and ammonium nitrate.The results suggested that the diploid hybrid tree species P.densata has a preference for nitrate and is not well adapted to ammonium-N as a sole nitrogen source regardless of the growth medium pH.Based on changes in environmental conditions,such as predicted future temperature increases in high altitude areas associated with climate change,P.densata is likely to be increasingly competitive and have wide adaptation in high altitude regions.
基金Supported by the National Natural Science Foundation of China(Nos.51279142 and 51379151)the Fundamental Research Fund for the Central Universities,China(No.204206020201)
文摘Understanding the interactions between salinity and fertilizers is of significant importance for enhancing crop yield and fertilizeruse efficiency. In this study a complete block design experiment was performed in the Hetao Irrigation District of Inner Mongolia,China, to evaluate the effects of interactions between soil salinity and nitrogen(N) application rate on sunflower photosynthesis and growth and to determine the optimum N application rate for sunflower growth in the district. Four levels of soil salinity expressed as electrical conductivity(0.33–0.60, 0.60–1.22, 1.2–2.44, and 2.44–3.95 dS m-1) and three application rates of N fertilization(90, 135,and 180 kg ha-1) were applied to 36 micro-plots. Soil salinity inhibited the photosynthetic rate, stomatal conductance, transpiration rate, plant height, leaf area, and aboveground dry matter of sunflowers. The intercellular CO2 concentration first decreased and then increased with increasing soil salinity in the seedling stage, and the instantaneous leaf water-use efficiency fluctuated with soil salinity. The stomatal and non-stomatal limitations of sunflowers alternated in the seedling stage; however, in the bud, blooming,and mature stages, the stomatal limitation was prevalent when the salinity level was lower than 2.44 dS m-1, whereas the nonstomatal limitation was predominant above the salinity level. The application of N fertilizer alleviated the adverse effects of salinity on sunflower photosynthesis and growth to some extent. During some key growth periods, such as the seedling and bud stages, a moderate N application rate(135 kg ha-1) resulted in the maximum photosynthetic rate and yielded the maximum dry matter. We suggest a moderate N application rate(135 kg ha-1) for the Hetao Irrigation District and other sunflower-growing areas with similar ecological conditions.
基金supported by the Indian Council of Cultural Relations and Egypt Government through the Cultural Exchange Programme
文摘The need to maintain high rice yields and improve fertilizer nitrogen(N)-use efficiency has fueled the use of tools such as leaf colour chart(LCC) and chlorophyll meter(SPAD meter) in managing fertilizer N based on colour of the leaf. Field experiments were conducted during 2011 to 2013 at Ludhiana, India to assess the need for basal N application and to establish critical threshold values of leaf greenness as measured by LCC and SPAD meter for formulating strategies for in-season management of fertilizer N in dry direct-seeded rice(DDSR). Avoiding application of N at sowing did not adversely affect rice grain yield, indicating that basal N application in DDSR was not necessary and might lead to reduced N-use efficiency. Monitoring N uptake rate during the growing season of DDSR suggested that N uptake rate peaked at the two growth stages: maximum tillering(42 to 56 days after sowing(DAS))and panicle initiation stages(70 to 84 DAS). Using the Cate-Nelson procedure, critical LCC and SPAD meter values for fertilizer N application worked out to be 4 and 37, respectively. Real-time fertilizer N management strategy based on applying 30 kg N ha-1whenever SPAD meter or LCC readings fell below the critical values maintained optimum rice yields along with higher N-use efficiency than that observed by following blanket recommendation for fertilizer N in the region. The fixed-time variable-dose strategy consisted of applying prescriptive doses of 20 kg N ha-1at 14 DAS and 30 kg N ha-1at 28 DAS and corrective doses of 30, 40 or 50 kg N ha-1at 49 and 70 DAS depending upon LCC shade to be ≥ 4, 4–3.5, or < 3.5 and SPAD meter readings to be ≥ 40, 40–35, or< 35, respectively. This strategy also resulted in optimal rice yield along with higher N-use efficiency as compared to the blanket recommendation. This study revealed that in DDSR, fertilizer N could be managed more efficiently using the tools of LCC and SPAD meter than the current blanket recommendation.
基金supported by the National Natural Science Foundation of China(31301267)the China Agriculture Research System(CARS-01)
文摘Zero-tillage has become increasingly attractive in rice production in China.This study was conducted to determine the feasibility of two possible improved N management practices with fewer N applications in zero-tillage rice:(1)two split applications of urea at75 kg N ha^(-1)at mid-tillering and 45 kg N ha^(-1)at panicle initiation(U_(120–2)),and(2)a single application of cross-linked polyacrylamide-coated urea(a slow-release fertilizer)at midtillering at a rate of 150 kg N ha^(-1)(PCU_(150–1)).Three field experiments were conducted to compare grain yield and N-use efficiency among several N treatments:a zero-N control(CK),U_(120–2),PCU_(150–1),a single application of urea at mid-tillering at a rate of 150 kg N ha^(-1)(U_(150–1)),and a commonly recommended N management practice for conventional tillage rice(three split applications of urea with 75 kg N ha^(-1)as basal,30 kg N ha^(-1)at mid-tillering,and 45 kg N ha^(-1)at panicle initiation)(U_(150–3)).Treatments with N application(U_(120–2),PCU_(150–1),U_(150–1),and U_(150–3))produced 1.08–3.16 t ha^(-1)higher grain yields than CK.Grain yields under both U_(120–2)and PCU_(150–1)were comparable to that in U_(150–3).Recovery efficiency of N(RE_N),agronomic N-use efficiency(AE_N)and partial factor productivity of applied N(PFP_N)were increased under U_(120–2)and were similar under PCU_(150–1)to those under U_(150–3).U_(150–1)showed lower grain yield,RE_N,AE_N,and PFP_Nthan U_(150–3).These results suggest that U_(150–3)can be replaced with U_(120–2)to achieve both an increase in N-use efficiency and a reduction in number of N applications and or by PCU_(150–1)to achieve a maximum reduction in number of N applications in zero-tillage rice production in China.
基金Supported by a Grant from the National Science Foundation to S. A.Heckathorn and E. W. Hamilton.
文摘More intense, more frequent, and longer heat-waves are expected in the future due to global warming, which could have dramatic ecological impacts. Increasing nitrogen （N） availability and its dynamics will likely impact plant responses to heat stress and carbon （C） sequestration in terrestrial ecosystems. This field study examined the effects of N availability on plant response to heat-stress （HS） treatment in naturally-occurring vegetation. HS （5 d at ambient or 40.5 ℃） and N treatments （±N） were applied to 16 1 m^2 plots in restored prairie vegetation dominated by Andropogon gerardii （warm-season C4 grass） and Solidago canadensis （warm-season C3 forb）. Before, during, and after HS, air, canopy, and soil temperature were monitored; net CO2 assimilation （Pn）, quantum yield of photosystem Ⅱ （ФpsⅡ）, stomatal conductance （gs）, and leaf water potential （ψw） of the dominant species and soil respiration （Rsoll） of each plot were measured daily during HS. One week after HS, plots were harvested, and C% and N% were determined for rhizosphere and bulk soil, and above-ground tissue （green/senescent leaf, stem, and flower）. Photosynthetic N-use efficiency （PNUE） and N resorption rate （NRR） were calculated. HS decreased Pn, gs, ψw, and PNUE for both species, and ＋N treatment generally increased these variables （±HS）, but often slowed their post-HS recovery. Aboveground biomass tended to decrease with HS in both species （and for green leaf mass in S. canadensis）, but decrease with ＋N for A. gerardii and increase with ＋N for S. canadensis. For A. gerardii, HS tended to decrease N% in green tissues with ＋N, whereas in S. canadensis, HS increased N% in green leaves. Added N decreased NRR for A. gerardii and HS increased NRR for S. canadensis. These results suggest that heat waves, though transient, could have significant effects on plants, communities, and ecosystem N cycling, and N can influence the effect of heat waves.
