Background:The spring phenology and growth strategy of temperate tree species can be strongly linked to their sensitivity to frosts,which deserve more profound investigations under the background of climate warming pa...Background:The spring phenology and growth strategy of temperate tree species can be strongly linked to their sensitivity to frosts,which deserve more profound investigations under the background of climate warming particularly considering the advancement of spring phenology as well as the increase in frequency and intensity of spring cold waves.Methods:Spring phenologies,stem radial growth characteristics,frost sensitivity of leaves and stem hydraulic systems were studied in five diffuse-porous and five ring-porous temperate tree species under a common garden condition.Results:The results showed that the spring leaf phenology of the diffuse-porous species was one to two weeks earlier than that of the ring-porous species.The ring-porous species had significantly higher stem hydraulic conductivity than the diffuse-porous species(1.81 and 0.95 kg·m^(-1)·s^(-1)·MPa^(-1),P<0.05)but were more vulnerable to freeze-thaw induced xylem embolism than the latter.After a simulated freeze-thaw event,the average percentage loss of hydraulic conductivity in the current year shoots increased from 26.0%(native embolism)to 86.7%in the ring-porous species,while it only increased from 21.3%to 38.3%in the diffuse-porous species.The spring phenology was clearly correlated with vulnerability to freeze-thaw induced embolism,with the more vulnerable ring-porous species exhibited substantially delayed phenology to reduce risks of catastrophic hydraulic dysfunction during spring frosts.Nevertheless,ring-porous species can offset the postponed onset of growth and gained even higher annual growth due to significantly higher hydraulic efficiency and leaf gas exchange rates.Conclusions:Contrasts between ring-porous and diffuse-porous species in resistance to freeze-thaw induced embolism suggest that they face different selective pressures from early spring frosts,which may at least be partially responsible for their divergence in spring phenology and growth strategy and can potentially lead to different responses to climate regime shifts.展开更多
Ultrasonic acoustic emissions （AEs） from leaf xylem of both water stressed and well watered potted winter wheat （Triticum aestivum L.） plants during drought and rewatering cycle were investigated with a ‘PCI-2 Ba...Ultrasonic acoustic emissions （AEs） from leaf xylem of both water stressed and well watered potted winter wheat （Triticum aestivum L.） plants during drought and rewatering cycle were investigated with a ‘PCI-2 Based AE System＇ （Physical Acoustics Corp. New Jersey, USA） for estimation of leaf xylem cavitation and embolism. Very few AEs occurred in xylem of wheat leaves in well-watered plant, and also in plant subject to mild and moderate soil water stress conditions over the first 4 d of the drought cycle. Great amounts of AEs have occurred since d 5 of the drought cycle as plant showed obvious leaf curling, indicating significant cavitation in leaf xylem on plant exposed to severe soil water deficit. At this point, relative soil water content （RSWC） and leaf xylem pressure （ψ1） dropped to 24.0-26.5% and -1.92 MPa, respectively, with reductions in leaf stomatal conductance （gs）, leaf transpiration （Tr） and leaf CO2 assimilation rate （A） of as much as 69.8, 60.7 and 46.5%, respectively. The effect of soil water deficit was in the order gs 〉 Tr 〉 A 〉 AE. Waveform physical property parameters such as amplitude, counts, rise time, duration, absolute energy and signal strength were analyzed. These parameters varied within very broad ranges, with frequency distribution of most parameters being well fitted by the exponential function y = yo- A exp （-x/t）. The proportion of stronger AE signals rose as soil dehydrated. While AEs occurrence in water stressed plant remained higher than in well-watered control at the following day after rewatering, waveform signal strength and related physical property parameters dropped immediately to that of control. Difference in AEs occurrence characterization between field-grown and potted wheat leaves was discussed.展开更多
Hydraulic vulnerability,the sensitivity of xylem embolism to water stress,is a major determinant trait associated with conifer mortality.This study investigated branch P50(50%hydraulic conductivity loss)of adult and j...Hydraulic vulnerability,the sensitivity of xylem embolism to water stress,is a major determinant trait associated with conifer mortality.This study investigated branch P50(50%hydraulic conductivity loss)of adult and juvenile ponderosa pines across multiple locations in the southwestern United States(SWUS),and examined relationships between P50 and climatic conditions,soil properties and forest management.Juvenile ponderosa pines had significantly more negative P50 values than adults on average.Both age groups exhibited a latitudinal pattern in P50 associated with regional climate conditions.Across the SWUS,juvenile P50 was positively correlated with growing season precipitation and temperature,and negatively correlated with soil pH and clay content.In some cases,significant differences in juvenile P50 between SWUS locations were associated with growing season moisture deficit,whereas other significant differences were less attributable to climate and may attest to potential genetic variation between populations.Climate variation,soil properties and population-level acclimation and/or adaptation may all influence the hydraulic vulnerability of juvenile ponderosa pines in the SWUS,promoting differences in stress tolerance of ponderosa pine forests across the region.展开更多
Variation in resistance of xylem to embolism among flowers,leaves,and stems strongly influences the survival and reproduction of plants.However,little is known about the vulnerability to xylem embolism under drought s...Variation in resistance of xylem to embolism among flowers,leaves,and stems strongly influences the survival and reproduction of plants.However,little is known about the vulnerability to xylem embolism under drought stress and their relationships to the anatomical traits of pits among reproductive and vegetative organs.In this study,we investigated the variation in xylem vulnerability to embolism in peduncles,petioles,and stems in a woody plant,Magnolia grandiflora.We analyzed the relationships between water potentials that induced 50%embolism(P50)in peduncles,petioles,and stems and the conduit pit traits hypothesized to influence cavitation resistance.We found that peduncles were more vulnerable to cavitation than petioles and stems,supporting the hypothesis of hydraulic vulnerability segmentation that leaves and stems are prioritized over flowers during drought stress.Moreover,P50 was significantly correlated with variation in the dimensions of inter-vessel pit apertures among peduncles,petioles and stems.These findings highlight that measuring xylem vulnerability to embolism in reproductive organs is essential for understanding the effect of drought on plant reproductive success and mortality under drought stress.展开更多
基金supported by the National Natural Science Foundation of China(Nos.31901284,31870593,31722013,32192431)the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences(No.ZDBS-LY-DQC019)National Key R&D Program of China(No.2020YFA0608100)。
文摘Background:The spring phenology and growth strategy of temperate tree species can be strongly linked to their sensitivity to frosts,which deserve more profound investigations under the background of climate warming particularly considering the advancement of spring phenology as well as the increase in frequency and intensity of spring cold waves.Methods:Spring phenologies,stem radial growth characteristics,frost sensitivity of leaves and stem hydraulic systems were studied in five diffuse-porous and five ring-porous temperate tree species under a common garden condition.Results:The results showed that the spring leaf phenology of the diffuse-porous species was one to two weeks earlier than that of the ring-porous species.The ring-porous species had significantly higher stem hydraulic conductivity than the diffuse-porous species(1.81 and 0.95 kg·m^(-1)·s^(-1)·MPa^(-1),P<0.05)but were more vulnerable to freeze-thaw induced xylem embolism than the latter.After a simulated freeze-thaw event,the average percentage loss of hydraulic conductivity in the current year shoots increased from 26.0%(native embolism)to 86.7%in the ring-porous species,while it only increased from 21.3%to 38.3%in the diffuse-porous species.The spring phenology was clearly correlated with vulnerability to freeze-thaw induced embolism,with the more vulnerable ring-porous species exhibited substantially delayed phenology to reduce risks of catastrophic hydraulic dysfunction during spring frosts.Nevertheless,ring-porous species can offset the postponed onset of growth and gained even higher annual growth due to significantly higher hydraulic efficiency and leaf gas exchange rates.Conclusions:Contrasts between ring-porous and diffuse-porous species in resistance to freeze-thaw induced embolism suggest that they face different selective pressures from early spring frosts,which may at least be partially responsible for their divergence in spring phenology and growth strategy and can potentially lead to different responses to climate regime shifts.
基金the support from the National Natural Science Foundation of China （NSFC） （30370848） Natural Science Foundation of Hebei Province, China （C2006000738）+1 种基金 A Special Program in Food Production Promotion of China： Integration and Extension of Crop Yielding-Promotion Management Techniques Under Wheat-Maize Double-Cropping System in Hebei Province, China （2004BA520A07） the Key Research Program of the Hebei Academy of Agricultural and Foestry Sciences, China （A03-1-02-14）.
文摘Ultrasonic acoustic emissions （AEs） from leaf xylem of both water stressed and well watered potted winter wheat （Triticum aestivum L.） plants during drought and rewatering cycle were investigated with a ‘PCI-2 Based AE System＇ （Physical Acoustics Corp. New Jersey, USA） for estimation of leaf xylem cavitation and embolism. Very few AEs occurred in xylem of wheat leaves in well-watered plant, and also in plant subject to mild and moderate soil water stress conditions over the first 4 d of the drought cycle. Great amounts of AEs have occurred since d 5 of the drought cycle as plant showed obvious leaf curling, indicating significant cavitation in leaf xylem on plant exposed to severe soil water deficit. At this point, relative soil water content （RSWC） and leaf xylem pressure （ψ1） dropped to 24.0-26.5% and -1.92 MPa, respectively, with reductions in leaf stomatal conductance （gs）, leaf transpiration （Tr） and leaf CO2 assimilation rate （A） of as much as 69.8, 60.7 and 46.5%, respectively. The effect of soil water deficit was in the order gs 〉 Tr 〉 A 〉 AE. Waveform physical property parameters such as amplitude, counts, rise time, duration, absolute energy and signal strength were analyzed. These parameters varied within very broad ranges, with frequency distribution of most parameters being well fitted by the exponential function y = yo- A exp （-x/t）. The proportion of stronger AE signals rose as soil dehydrated. While AEs occurrence in water stressed plant remained higher than in well-watered control at the following day after rewatering, waveform signal strength and related physical property parameters dropped immediately to that of control. Difference in AEs occurrence characterization between field-grown and potted wheat leaves was discussed.
基金supported by grants from the USDA Forest Service,Western Wildlands Environmental Threat Assessment Center(20-JV-11221634-190)the US Geological Survey Southwest Climate Adaptation Science Center(G20AC00440-01)the U.S.National Science Foundation(NSF 2020185).
文摘Hydraulic vulnerability,the sensitivity of xylem embolism to water stress,is a major determinant trait associated with conifer mortality.This study investigated branch P50(50%hydraulic conductivity loss)of adult and juvenile ponderosa pines across multiple locations in the southwestern United States(SWUS),and examined relationships between P50 and climatic conditions,soil properties and forest management.Juvenile ponderosa pines had significantly more negative P50 values than adults on average.Both age groups exhibited a latitudinal pattern in P50 associated with regional climate conditions.Across the SWUS,juvenile P50 was positively correlated with growing season precipitation and temperature,and negatively correlated with soil pH and clay content.In some cases,significant differences in juvenile P50 between SWUS locations were associated with growing season moisture deficit,whereas other significant differences were less attributable to climate and may attest to potential genetic variation between populations.Climate variation,soil properties and population-level acclimation and/or adaptation may all influence the hydraulic vulnerability of juvenile ponderosa pines in the SWUS,promoting differences in stress tolerance of ponderosa pine forests across the region.
基金the National Natural Science Foundation of China(31670415,31870385,31960224)the"Young Top Talents"Ten Thousands Plan in Yunnan Province(YNWR-QNBJ-2018-337)Science research of Yunnan Provincial Department of Education(2019J1068)and open funding from the CAS Key Laboratory of Tropical Forest Ecology to F.P.Zhang.
文摘Variation in resistance of xylem to embolism among flowers,leaves,and stems strongly influences the survival and reproduction of plants.However,little is known about the vulnerability to xylem embolism under drought stress and their relationships to the anatomical traits of pits among reproductive and vegetative organs.In this study,we investigated the variation in xylem vulnerability to embolism in peduncles,petioles,and stems in a woody plant,Magnolia grandiflora.We analyzed the relationships between water potentials that induced 50%embolism(P50)in peduncles,petioles,and stems and the conduit pit traits hypothesized to influence cavitation resistance.We found that peduncles were more vulnerable to cavitation than petioles and stems,supporting the hypothesis of hydraulic vulnerability segmentation that leaves and stems are prioritized over flowers during drought stress.Moreover,P50 was significantly correlated with variation in the dimensions of inter-vessel pit apertures among peduncles,petioles and stems.These findings highlight that measuring xylem vulnerability to embolism in reproductive organs is essential for understanding the effect of drought on plant reproductive success and mortality under drought stress.
