Changes In Stomatal Conductance Research Articles

Unexpected Connections between Humidity and Ion Transport Discovered Using a Model to Bridge Guard Cell-to-Leaf Scales.

Stomatal movements depend on the transport and metabolism of osmotic solutes that drive reversible changes in guard cell volume and turgor. These processes are defined by a deep knowledge of the identities of the key transporters and of their biophysical and regulatory properties, and have been modeled successfully with quantitative kinetic detail at the cellular level. Transpiration of the leaf and canopy, by contrast, is described by quasilinear, empirical relations for the inputs of atmospheric humidity, CO2, and light, but without connection to guard cell mechanics. Until now, no framework has been available to bridge this gap and provide an understanding of their connections. Here, we introduce OnGuard2, a quantitative systems platform that utilizes the molecular mechanics of ion transport, metabolism, and signaling of the guard cell to define the water relations and transpiration of the leaf. We show that OnGuard2 faithfully reproduces the kinetics of stomatal conductance in Arabidopsis thaliana and its dependence on vapor pressure difference (VPD) and on water feed to the leaf. OnGuard2 also predicted with VPD unexpected alterations in K+ channel activities and changes in stomatal conductance of the slac1 Cl- channel and ost2 H+-ATPase mutants, which we verified experimentally. OnGuard2 thus bridges the micro-macro divide, offering a powerful tool with which to explore the links between guard cell homeostasis, stomatal dynamics, and foliar transpiration.

Climate signals in tree-ring δ18 O and δ13 C from southeastern Tibet: insights from observations and forward modelling of intra- to interdecadal variability.

Stable isotopes in tree rings are increasingly used as proxies for climatic and ecophysiological changes. However, uncertainties remain about the strength and consistency of their response to environmental variation at different temporal (i.e. seasonal to inter-decadal) scales. We developed 5yr of intra-seasonal and 62yr of early- and late-wood δ13 C and δ18 O series of Smith fir (Abies georgei var. smithii) on the southeastern Tibetan Plateau, and used a process-based forward model to examine the relative importance of environmental and physiological controls on the isotopic data. In this temperate high-altitude region, the response, both δ18 O and δ13 C, is primarily to variations in relative humidity, but by different processes. In δ18 O, the response is via source water δ18 O but also arises from leaf water 18 O enrichment. In δ13 C, the response is via changes in stomatal conductance but is modified by carry-over effects from prior periods. We conclude that tree-ring δ18 O may be a more robust climate proxy than δ13 C, and δ13 C may be more suited to studies of site-related physiological responses to the local environment.

Temporal network analysis identifies early physiological and transcriptomic indicators of mild drought in Brassica rapa.

The dynamics of local climates make development of agricultural strategies challenging. Yield improvement has progressed slowly, especially in drought-prone regions where annual crop production suffers from episodic aridity. Underlying drought responses are circadian and diel control of gene expression that regulate daily variations in metabolic and physiological pathways. To identify transcriptomic changes that occur in the crop Brassica rapa during initial perception of drought, we applied a co-expression network approach to associate rhythmic gene expression changes with physiological responses. Coupled analysis of transcriptome and physiological parameters over a two-day time course in control and drought-stressed plants provided temporal resolution necessary for correlation of network modules with dynamic changes in stomatal conductance, photosynthetic rate, and photosystem II efficiency. This approach enabled the identification of drought-responsive genes based on their differential rhythmic expression profiles in well-watered versus droughted networks and provided new insights into the dynamic physiological changes that occur during drought.

Effect of waterlogging on carbon isotope discrimination during photosynthesis in Larix gmelinii

ABSTRACTSoil moisture is a major factor controlling carbon isotope discrimination (Δ13C), which has been demonstrated to decrease under dry conditions in many studies; however, few studies on Δ13C under waterlogging condition have been conducted. In this study, a pot experiment was conducted with Larix gmelinii, a major larch species in the east Siberian Taiga, to investigate the effect of waterlogging on Δ13C during photosynthesis. Assimilation rate and Δ13CRD (instantaneous Δ13C calculated with Rayleigh distillation equation) decreased drastically soon after waterlogging, followed by recovery in their values, which was caused by a change in stomatal conductance. Thereafter, assimilation rate decreased gradually, whereas Δ13CRD decreased more gently. These results were thought to be caused by the decrease in both stomatal conductance and carboxylation. Our results indicate that extreme wet events may cause a decrease in Δ13C, which is important information for detecting flooding events in the past using tree-ring isotope analyses and for studying impacts of flooding on plants in areas where waterlogging might occur.

Herbivore perception decreases photosynthetic carbon assimilation and reduces stomatal conductance by engaging 12-oxo-phytodienoic acid, mitogen-activated protein kinase 4 and cytokinin perception.

Herbivory-induced changes in photosynthesis have been documented in many plant species; however, the complexity of photosynthetic regulation and analysis has thwarted progress in understanding the mechanism involved, particularly those elicited by herbivore-specific elicitors. Here, we analysed the early photosynthetic gas exchange responses in Nicotiana attenuata plants after wounding and elicitation with Manduca sexta oral secretions and the pathways regulating these responses. Elicitation with M. sexta oral secretions rapidly decreased photosynthetic carbon assimilation (AC ) in treated and systemic (untreated, vascularly connected) leaves, which were associated with changes in stomatal conductance, rather than with changes in Rubisco activity and 1-5 ribulose-1,5-bisphosphate turnover. Phytohormone profiling and gas exchange analysis of oral secretion-elicited transgenic plants altered in phytohormone regulation, biosynthesis and perception, combined with micrografting techniques, revealed that the local photosynthetic responses were mediated by 12-oxo-phytodienoic acid, while the systemic responses involved interactions among jasmonates, cytokinins and abscisic acid signalling mediated by mitogen-activated protein kinase 4. The analysis also revealed a role for cytokinins interacting with mitogen-activated protein kinase 4 in CO2 -mediated stomatal regulation. Hence, oral secretions, while eliciting jasmonic acid-mediated defence responses, also elicit 12-oxo-phytodienoic acid-mediated changes in stomatal conductance and AC , an observation illustrating the complexity and economy of the signalling that regulates defence and carbon assimilation pathways in response to herbivore attack.

Cell-level anatomical characteristics explain high mesophyll conductance and photosynthetic capacity in sclerophyllous Mediterranean oaks.

Leaf mass per area (LMA) has been suggested to negatively affect the mesophyll conductance to CO2 (gm ), which is the most limiting factor for area-based photosynthesis (AN ) in many Mediterranean sclerophyll species. However, despite their high LMA, these species have similar AN to plants from other biomes. Variations in other leaf anatomical traits, such as mesophyll and chloroplast surface area exposed to intercellular air space (Sm /S and Sc /S), may offset the restrictions imposed by high LMA in gm and AN in these species. Seven sclerophyllous Mediterranean oaks from Europe/North Africa and North America with contrasting LMA were compared in terms of morphological, anatomical and photosynthetic traits. Mediterranean oaks showed specific differences in AN that go beyond the common morphological leaf traits reported for these species (reduced leaf area and thick leaves). These variations resulted mainly from the differences in gm , the most limiting factor for carbon assimilation in these species. Species with higher AN showed increased Sc /S, which implies increased gm without changes in stomatal conductance. The occurrence of this anatomical adaptation at the cell level allowed evergreen oaks to reach AN values comparable to congeneric deciduous species despite their higher LMA.

Significant contribution from foliage-derived ABA in regulating gas exchange in Pinus radiata.

The complex regulatory system controlling stomata involves physical and chemical signals that affect guard cell turgor to bring about changes in stomatal conductance (gs). Abscisic acid (ABA) closes stomata, yet the mechanisms controlling foliar ABA status in tree species remain unclear. The importance of foliage-derived ABA in regulating gas exchange was evaluated under treatments that affected phloem export through girdling and reduced water availability in the tree species, Pinus radiata (D. Don). Branch- and whole-plant girdling increased foliar ABA levels leading to declines in gs, despite no change in plant water status. Changes in gs were largely independent of the more transient increases in foliar non-structural carbohydrates (NSC), suggesting that gradual accumulation of foliar ABA was the primary mechanism for reductions in gs and assimilation. Whole-plant girdling eventually reduced root NSC, hindering root water uptake and decreasing foliar water potential, causing a dramatic increase in ABA level in leaves and concentrations in the xylem sap of shoots (4032 ng ml-1), while root xylem sap concentrations remained low (43 ng ml-1). Contrastingly, the drought treatment caused similar increases in xylem sap ABA in both roots and shoots, suggesting that declines in water potential result in relatively consistent changes in ABA along the hydraulic pathway. ABA levels in plant canopies can be regulated independently of changes in root water status triggered by changes by both phloem export and foliar water status.

Contrasting hydraulic strategies in Salix psammophila and Caragana korshinskii in the southern Mu Us Desert, China

AbstractSalix psammophila and Caragana korshinskii are two common shrubs in the southern Mu Us Desert, China. Their hydraulic strategies for adapting to this harsh, dry desert environment are not yet clear. This study examined the hydraulic transport efficiency, vulnerability to cavitation, and daily embolism refilling in the leaves and stems of these two shrubs during the dry season. In order to gain insight into water use strategies of whole plants, other related traits were also considered, including daily changes in stomatal conductance, leaf mass per area, leaf pressure–volume parameters, wood density and the Huber value. The leaves and stems of S. psammophila had greater hydraulic efficiency, but were more vulnerable to drought‐induced hydraulic dysfunction than C. korshinskii. The difference between leaf and stem water potential at 50 % loss of conductivity was 0.12 MPa for S. psammophila and 0.81 MPa for C. korshinskii. Midday stomatal conductance decreased by 74 % compared to that at 8:30 in S. psammophila, whereas no change occurred in C. korshinskii. Daily embolism and refilling occurred in the stems of S. psammophila and leaves of C. korshinskii. These results suggest that a stricter stomatal regulation, daily embolism repair in stems, and a higher stem water capacitance could be partially compensating for the greater susceptibility to xylem embolism in S. psammophila, whereas higher leaf elastic modulus, greater embolism resistance in stems, larger difference between leaf and stem hydraulic safety, and drought‐induced leaf shedding in C. korshinskii were largely responsible for its more extensive distribution in arid and desert steppes.

Disentangling the Effects of Precipitation Amount and Frequency on the Performance of 14 Grassland Species.

Climate change is causing shifts in the amount and frequency of precipitation in many regions, which is expected to have implications for plant performance. Most research has examined the impacts of the amount of precipitation on plants rather than the effects of both the amount and frequency of precipitation. To understand how climate-driven changes in precipitation can affect grassland plants, we asked: (i) How does the amount and frequency of precipitation affect plant performance? (ii) Do plant functional groups vary in their response to variable precipitation? To answer these questions we grew 14 monocot and eudicot grassland species and conducted a factorial manipulation of the amount (70 vs 90mm/month) and frequency (every 3, 15, or 30 days) of precipitation under rainout shelters. Our results show that both the amount and frequency of precipitation impact plant performance, with larger effects on eudicots than monocots. Above- and below-ground biomass were affected by the amount of precipitation and/or the interaction between the amount and frequency of precipitation. Above-ground biomass increased by 21–30% when the amount of precipitation was increased. When event frequency was decreased from 3 to 15 or 30 days, below-ground biomass generally decreased by 18–34% in the 70 mm treatment, but increased by 33–40% in the 90 mm treatment. Changes in stomatal conductance were largely driven by changes in event frequency. Our results show that it is important to consider changes in both the amount and frequency of precipitation when predicting how plant communities will respond to variable precipitation.

Response of tree growth and wood structure of Larix kaempferi, Kalopanax septemlobus and Betula platyphylla saplings to elevated CO2 concentration for 5 years exposure in a FACE system

Elevated CO 2 concentration affected biomass partitioning in above-ground biomass, but size and number of water-conducting cells were unchanged in Larix kaempferi, Kalopanax septemlobus and Betula platyphylla. Using a Free-Air CO2 Enrichment (FACE) system, we studied the effect of elevated CO2 on the growth, leaf gas exchange and xylem anatomy of a conifer, Larix kaempferi, and two angiospermous tree species, Kalopanax septemlobus and Betula platyphylla. Two-year-old seedlings were grown at control sites (ambient; 370 ppm) and FACE sites (elevated; 500 ppm) for 5 years. We measured the lumen area and number of water-conducting cells, as well as biomass and leaf gas exchange, and visualized the functional region of water transport using a dye injection experiment. Elevated CO2 did not induce any significant changes in growth or in leaf gas exchange or lumen area of earlywood tracheids in L. kaempferi relative to ambient CO2. In two other tree species, elevated CO2 was found to enhance tree height and total leaf area (LA), with no change in stomatal conductance. In K. septemlobus, there were no changes in lumen area or number of earlywood vessels, or in the functional region of water transport. B. platyphylla also underwent no changes in lumen area or number of vessels, although there was a yearly variation in the size of the vessels. Our results show that 5 years of CO2 exposure did not notably affect the anatomical features of water-conducting cells. This finding suggests that, under elevated CO2, trees respond to changes in water balance due to changes in LA by extending the hydraulically active area of xylem.

The effect of vapour pressure deficit on stomatal conductance, sap pH and leaf-specific hydraulic conductance in Eucalyptus globulus clones grown under two watering regimes.

Stomatal conductance has long been considered of key interest in the study of plant adaptation to water stress. The expected increase in extreme meteorological events under a climate change scenario may compromise survival in Eucalyptus globulus plantations established in south-western Spain. We investigated to what extent changes in stomatal conductance in response to high vapour pressure deficits and water shortage are mediated by hydraulic and chemical signals in greenhouse-grown E. globulus clones. Rooted cuttings were grown in pots and submitted to two watering regimes. Stomatal conductance, shoot water potential, sap pH and hydraulic conductance were measured consecutively in each plant over 4 weeks under vapour pressure deficits ranging 0·42 to 2·25 kPa. Evapotranspiration, growth in leaf area and shoot biomass were also determined. There was a significant effect of both clone and watering regime in stomatal conductance and leaf-specific hydraulic conductance, but not in sap pH. Sap pH decreased as water potential and stomatal conductance decreased under increasing vapour pressure deficit. There was no significant relationship between stomatal conductance and leaf-specific hydraulic conductance. Stomata closure precluded shoot water potential from falling below -1·8 MPa. The percentage loss of hydraulic conductance ranged from 40 to 85 %. The highest and lowest leaf-specific hydraulic conductances were measured in clones from the same half-sib families. Water shortage reduced growth and evapotranspiration, decreases in evapotranspiration ranging from 14 to 32 % in the five clones tested. Changes in sap pH seemed to be a response to changes in atmospheric conditions rather than soil water in the species. Stomata closed after a considerable amount of hydraulic conductance was lost, although intraspecific differences in leaf-specific hydraulic conductance suggest the possibility of selection for improved productivity under water-limiting conditions combined with high temperatures in the early stages of growth.

Comprehensive tissue-specific proteome analysis of drought stress responses in Pennisetum glaucum (L.) R. Br. (Pearl millet)

Pearl millet is the fifth most important cereal crop worldwide and cultivated especially by small holder farmers in arid and semi-arid regions because of its drought and salt tolerance. The molecular mechanisms of drought stress tolerance in Pennisetum remain elusive. We have used a shotgun proteomics approach to investigate protein signatures from different tissues under drought and control conditions. Drought stressed plants showed significant changes in stomatal conductance and increased root growth compared to the control plants. Root, leaf and seed tissues were harvested and 2281 proteins were identified and quantified in total. Leaf tissue showed the largest number of significant changes (120), followed by roots (25) and seeds (10). Increased levels of root proteins involved in cell wall-, lipid-, secondary- and signaling metabolism and the concomitantly observed increased root length point to an impaired shoot–root communication under drought stress. The harvest index (HI) showed a significant reduction under drought stress. Proteins with a high correlation to the HI were identified using sparse partial least square (sPLS) analysis. Considering the importance of Pearl millet as a stress tolerant food crop, this study provides a first reference data set for future investigations of the underlying molecular mechanisms. Biological significanceDrought stress is the most limiting factor for plant growth and crop production worldwide. At the same time drought susceptible cereal crops are among the largest producers worldwide. In contrast, Pearl millet is a drought and salt tolerant cereal crop especially used in arid and semi-arid regions by small farmers. The multifactorial molecular mechanisms of this unique drought tolerance are not known. Here, we employ shotgun proteomics for a first characterization of the Pearl millet drought stress proteome. The experimental setup and the data set generated from this study reveal comprehensive physiological and proteomic responses of the drought stressed Pearl millet plants. Our study reveals statistically significant tissue-specific protein signatures during the adaptation to drought conditions. Thus, the work provides a first reference study of the drought stress proteome and related drought responsive proteins (DRP's) in Pearl millet.

Response of Quercus velutina growth and water use efficiency to climate variability and nitrogen fertilization in a temperate deciduous forest in the northeastern USA.

Nitrogen (N) deposition and changing climate patterns in the northeastern USA can influence forest productivity through effects on plant nutrient relations and water use. This study evaluates the combined effects of N fertilization, climate and rising atmospheric CO2on tree growth and ecophysiology in a temperate deciduous forest. Tree ring widths and stable carbon (δ(13)C) and oxygen (δ(18)O) isotopes were used to assess tree growth (basal area increment, BAI) and intrinsic water use efficiency (iWUE) ofQuercus velutinaLamb., the dominant tree species in a 20+ year N fertilization experiment at Harvard Forest (MA, USA). We found that fertilized trees exhibited a pronounced and sustained growth enhancement relative to control trees, with the low- and high-N treatments responding similarly. All treatments exhibited improved iWUE over the study period (1984-2011). Intrinsic water use efficiency trends in the control trees were primarily driven by changes in stomatal conductance, while a stimulation in photosynthesis, supported by an increase in foliar %N, contributed to enhancing iWUE in fertilized trees. All treatments were predominantly influenced by growing season vapor pressure deficit (VPD), with BAI responding most strongly to early season VPD and iWUE responding most strongly to late season VPD. Nitrogen fertilization increasedQ. velutinasensitivity to July temperature and precipitation. Combined, these results suggest that ambient N deposition in N-limited northeastern US forests has enhanced tree growth over the past 30 years, while rising ambient CO2has improved iWUE, with N fertilization and CO2having synergistic effects on iWUE.

Measuring and modelling CO2 effects on sugarcane

In order to fully capture the benefits of rising CO2 in adapting agriculture to climate change, we first need to understand how CO2 affects crop growth. Several recent studies reported unexpected increases in sugarcane (C4) yields under elevated CO2, but it is difficult to distinguish direct leaf-level effects of rising CO2 on photosynthesis from indirect water-related responses. A simulation model of CO2 effects, based purely on changes in stomatal conductance (indirect mechanism), showed transpiration was reduced by 30% (initially) to 10% (closed canopy) and yield increased by 3% even in a well-irrigated crop. The model incorporated the results of a field experiment, and a glasshouse experiment designed to disentangle the mechanisms of CO2 response: whole-plant transpiration and stomatal conductance were both 28% lower for plants growing with high-frequency demand-based watering at 720 vs 390 ppm CO2, but there was no increase in biomass, indicating that indirect mechanisms dominate CO2 responses in sugarcane.

内蒙古荒漠草原植物遗传多样性对模拟增温处理的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 内蒙古荒漠草原植物遗传多样性对模拟增温处理的响应 DOI: 10.5846/stxb201504220826 作者: 作者单位: 中国农业科学院草原研究所;内蒙古农业大学生命科学学院,中国农业科学院草原研究所：内蒙古农业大学生命科学学院,中国农业科学院草原研究所,中国农业科学院草原研究所,内蒙古农业大学生态与环境学院,中国农业科学院草原研究所;内蒙古农业大学生命科学学院 作者简介: 通讯作者: 中图分类号: 基金项目: 内蒙古自治区自然科学基金资助项目（2015MS0305）；中国科学院西部之光“人才培养”项目；中国农业科学院草原研究所科技创新工程资助项目 The response of genetic diversity in desert steppe plants to simulated warming in Inner Mongolia, China Author: Affiliation: Institute of Grassland Research, Chinese Academy of Agricultural Sciences;College of Life Sciences, Inner Mongolia Agricultural University,,,,,Institute of Grassland Research, Chinese Academy of Agricultural Sciences;College of Life Science, Inner Mongolia Agricultural University, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为探究全球变暖对温带荒漠草原地上种群的遗传影响，对已经接受模拟增温处理6年的短花针茅草原4种不同生活型植物，即半灌木、多年生禾草、多年生杂类草和一年生植物，应用AFLP分子标记方法研究了其遗传多样性和遗传结构。结果显示，对照处理与增温处理下的木地肤、短花针茅、细叶葱、猪毛菜4种植物的多态位点百分率（PPB）分别为11.32%，11.32%；40.83%，39.91%；14.29%，13.10%；19.85%，19.12%。Nei's基因多样性指数（He）分别为0.0274，0.0259；0.0812，0.0899；0.0131，0.0084；0.0506，0.0456。Shannon's信息指数值（I）分别为0.0447，0.0430；0.1354，0.1466；0.0267，0.0182；0.0811，0.0733。分子方差分析（AMOVA）显示4种植物的变异主要来源于实验处理内部，木地肤为85.03%，短花针茅为66.35%，细叶葱为70.00%，猪毛菜为66.52%；增温处理间的变异分别占-2.81%，-5.47%，-3.60%，2.53%（P>0.05）。4种植物增温处理与变异程度之间在统计学上并无相关性。研究表明虽然短时间的模拟增温并不足以使4种生活型植物种群遗传多样性和遗传结构发生显著变化，但相对于3种多年生植物，一年生植物猪毛菜更容易受到增温影响。多年生和一年生植物对增温具有不同的遗传响应。 Abstract:Climate is the most important factor that determines vegetation types and the distribution of species, and, accordingly, these features are two of the most prominent indicators of climate change. Currently, scientists generally agree that climate change will inevitably lead to changes in plant community structure and function, and if this change continues, the effects will be profound and enduring. Existing research shows that simulated warming causes an increase in biomass in Deschampsia caespitosa, Carex alrofusca, and Leymus chinensis; as climates change, these constructive species and their main companion species within a Kobresia humilis meadow have experienced an advancement in their spring phenology and a delay in their autumn phenophase. In addition, the photosynthetic rate of Deschampsia caespitosa in a Northwest Sichuan alpine meadow has increased. Although the change in stomatal conductance was irregular, a significant decrease has also been observed in the sodium, potassium, and phosphorus content of leaves. However, relatively little research has been conducted on the effects of simulated warming on the genetic structure and diversity of plant populations. Against the background of global climate change, the temperatures of the Inner Mongolian desert steppe have become unevenly elevated, with average annual temperatures increasing from 8.1℃ in the 1950s to 9.0℃ in the 1990s. The present study explores the effects of global warming on the genetics of wild forage plant populations with different life forms in desert steppe habitat, in an effort to elucidate their potential to adapt to environmental change. The study site was located in the desert steppe in Siziwangqi territory of Inner Mongolia. Suspension infrared radiators were used to create a controlled warming experiment under otherwise natural field conditions. Warming began on May 3, 2006. The average soil temperature at depths of 0, 7.5, 15, 30, and 50 cm increased by 1.32, 0.92, 0.88, 0.80, and 0.74℃, respectively, after warming for 1 year compared with the average in plots not exposed to warming. For this study, changes in genetic diversity and structure were analyzed in four plant populations: (1) small half shrubs, represented by Kochia prostrata; (2) perennial grasses, represented by Stipa breviflora; (3) perennial forbs, represented by Allium tenuissimum; and (4) annuals and biennials, represented by Salsola collina). The study was conducted under simulated warming pressure and genetic analysis was performed using amplified fragment length polymorphism. The percentages of polymorphic loci in K. prostrata, S. breviflora, A. tenuissimum, and S. collina under non-warming were 11.32%, 40.83%, 14.29%, and 19.85%, whereas those under simulated warming were 11.32%, 39.91%, 13.10%, and 19.12%, respectively. The genetic diversity of the four populations measured under control and simulated warming, measured by the Shannon's information index, were as follows: K. prostrata (0.0274, 0.0259), S. breviflora (0.0812, 0.0899), Allium tenuissimum (0.0131, 0.0084), and S. collina (0.0506, 0.0456). These findings exhibited the same distributional pattern as that of Nei's genetic diversity index for K. prostrata (0.0447, 0.0430), S. breviflora (0.1354, 0.1466), Allium tenuissimum (0.0267, 0.0182), and S. collina (0.0811, 0.0733). Cluster analysis of these four species showed that known of the species reacted significantly to the warming process, and that inter-individual clusters were not significantly different. The results of an analysis of molecular variance (AMOVA) indicated that the main source of variation among the four life form populations was within-population variation: K. prostrata (85.03%), S. breviflora (66.35%), A. tenuissimum (70.00%), and S. collina (66.52%). The among-groups variation was not significant and accounted for the following percentages of variation: K. prostrata (-2.81%), S. breviflora (-5.47%), Allium tenuissimum (-3.60%), and S. collina (2.53%). No statistically significant correlation was found between simulated warming and genetic differentiation. This study shows that a short period of simulated warming was not sufficient to create a significant change in genetic diversity and structure for the four life form populations studied here; however, compared with the three types of perennials studied, the annual plant S. collina, is more susceptible to the effects of warming. Perennials and annuals have different genetic responses to warming. This study provides experimental evidence that can reveal the potential adaptation of plants to environmental change for different life forms of wild forage plants of the desert steppe, and will help researchers to predict forage yield and changes in forage quality. 参考文献 相似文献 引证文献

The dynamics of radial sap flux density reflects changes in stomatal conductance in response to soil and air water deficit

Water scarcity in semiarid regions of Europe threatens the sustainability of fruit tree orchards unless irrigation water is optimized and scheduled in deficit irrigation strategies. Stomatal conductance (gs) is one of the best indicators of plant water stress, since it is placed in the crossroad between water and CO2 fluxes at the leaf level. Unfortunately, it is not possible to measure gs automatically and continuously, which reduces its potential for irrigation scheduling. In this work we examined the use of sap flux density (Js) in the outer rings of the sapwood of olive trees as a surrogate of gs. The working hypothesis was that as olive trees are well-coupled to atmosphere because of their small leaves, the ratio of Js to air vapor pressure deficit (D) should correlate well with the dynamics of gs in the canopy. It was also expected that current year, sun exposed leaves were mainly connected to the outer rings of the sapwood, and the oldest, shaded leaves to the inner rings. This was tested by measuring gs in new, sun-exposed leaves vs gs in old, shaded leaves. Both hypotheses were contrasted and our results confirmed that gs can be estimated from Js/D (R2 of the relationships were always higher than 0.8). A wide range of estimated gs values (0.350–0.025molm−2s−1) were derived from Js measurements in an olive orchard under three different irrigation regimes. Results were satisfactory and open the possibility of applying this method to estimate gs and use it either as a reliable water stress indicator or in transpiration and photosynthesis models applied to fruit tree orchards under a wide range of water stress conditions.

Improvement of water and light availability after thinning at a xeric site: which matters more? A dual isotope approach.

Thinning fosters individual tree growth by increasing the availability of water, light and nutrients. At sites where water rather than light is limiting, thinning also enhances soil evaporation and might not be beneficial. Detailed knowledge of the short- to long-term physiological response underlying the growth responses to thinning is crucial for the management of forests already suffering from recurrent drought-induced dieback. We applied a dual isotope approach together with mechanistic isotope models to study the physiological processes underlying long-term growth enhancement of heavily thinned Pinus sylvestris in a xeric forest in Switzerland. This approach allowed us to identify and disentangle thinning-induced changes in stomatal conductance and assimilation rate. At our xeric study site, the increase in stomatal conductance far outweighed the increase in assimilation, implying that growth release in heavily thinned trees is primarily driven by enhanced water availability rather than increased light availability. We conclude that in forests with relatively isohydric species (drought avoiders) that are growing close to their physiological limits, thinning is recommended to maintain a less negative water balance and thus foster tree growth, and ultimately the survival of forest trees under drought.

Water use efficiency in peach trees over a four-years experiment on the effects of irrigation and nitrogen application

The optimization of crop water productivity is a key objective in modern agriculture. Deficit irrigation is a widely used strategy when water and energy are scarce and/or expensive. However, in fruit tree crops, the severity and duration of water stress can affect yield and fruit size, thus imposing severe limitations on the effectiveness of production processes, and on fruit quality and water productivity. Here we analyzed water use efficiency (WUE) of peach trees over four years both in agronomic terms, as water productivity of fruits and biomass (WUEWPy,b), and in physiological terms, as intrinsic and instantaneous leaf WUE (WUEint and WUEins respectively). Our results show a positive and additive effect of water and nitrogen application on WUEWP, reflected by yield enhancement. WUEint and WUEins varied through changes in stomatal conductance and transpiration—two parameters that are determined by plant water status and nitrogen application. Our results suggest that the variation in WUEWPy was caused by complex regulation of plant growth and fruiting, related to water status and nitrogen availability, which both drive plant WUE. In order to evaluate WUE at the canopy scale, we studied δ13C and δ18O in wood. These parameters were found to be related to leaf stomatal conductance and transpiration and also to the effects of irrigation and nitrogen; however, no clear relationship was observed with WUEWPy. Plant water status was also dependent on crop load and vegetative growth and was strongly associated with WUEWPy and WUEWPb. Taken together, our results show that full irrigation and rational nitrogen application can improve WUEWPy, both in agronomic and economic terms. When water deficit conditions are foreseeable, deficit irrigation in fruit growth phase III (GSIII) is a more profitable strategy that when applied in phase II (GSII). In this regard, flexible deficit irrigation in GSIII is an affordable and practical tool to include in strategies aiming to improve water and nitrogen use efficiency in fruit crops when water is scarce.

Effects of kaolin-based particle film and fruit zone netting on Cabernet Sauvignon grapevine physiology and fruit quality

<p style="text-align: justify;"><strong>Aims</strong>: Long exposure to high temperatures or UV-radiation may induce negative effects on vine physiology and grape composition. Here, the effects of two methods to moderate radiation and temperature in the fruit zone of a Cabernet Sauvignon vineyard were evaluated against a control.</p><p style="text-align: justify;"><strong>Methods and results</strong>: The treatments assessed were: (a) periodical spraying of kaolin on leaves and bunches and (b) fruit zone netting with a Raschell’s type mesh. The kaolin-based treatment increased the reflectance of light and moderately reduced fruit temperature (~1ºC below the control), whilst the shading net caused a significant reduction in radiation and temperature in the fruit zone (~7ºC below the control). The Net treatment showed lower (more negative) stem water potential values than the control, but did not persist until the end of the trial. Also, none of the treatments led to significant changes in stomatal conductance, transpiration or CO<sub>2</sub> assimilation throughout the season. However, the incidence and severity of fruit dehydration was significantly lower in the treated plants compared to the control. Finally, no differences in fruit chemical composition were observed between the treatments and the control.</p><p style="text-align: justify;"><strong>Conclusion</strong>: Under the conditions of this trial, both treatments tested were sufficient in moderating the negative effects of excess radiation or high temperature on grape berries.</p><strong>Significance and impact of the study</strong>: Kaolin-based particle spraying and fruit zone netting were proved to be feasible practical alternatives to lessen the negative effects of excess radiation or high temperature on grape berries, under hot climate.

Diurnal changes in photosynthesis in Sclerocarya birrea from South Africa and Israel after introduction and acclimatization in Wenshan, Yunnan Province, China

Photosynthetic activity is one of the most important indicators for evaluating the introduction and acclimatization of trees to new geographies. The aim of this study was to investigate the photosynthetic characteristics of marula [Sclerocarya birrea (A. Rich.) Hochst. subsp. caffra (Sond.) Kokwaro (Anacardiaceae)] and the environmental conditions relevant to its growth in China. We analyzed the diurnal dynamics of photosynthesis in two S. birrea varieties, one from South Africa and one from Israel, after introduction into China using a portable photosynthesis measuring system. Our results showed that the diurnal net photosynthetic rate (Pn) exhibited an atypical double-peak pattern that was influenced mainly by stomatal factors. Moreover, the diurnal change in stomatal conductance (Gs) was consistent with that for Pn and showed an obvious double-peak curve, whereas the diurnal change in the transpiration rate (Tr) was opposite to that in intercellular CO2 concentration (Ci), which presented a single-peak curve. The extreme values of the environmental factors we monitored occurred at approximately the same time of day and influenced photosynthesis by affecting Ci, Tr, and leaf temperature (TL), with light intensity exerting an especially strong effect. The Pn of the S. birrea variety from Israel was higher than that of the S. birrea variety from South Africa, while South Africa S. birrea exhibited superior growth trait in southern China. We suggest that the photosynthetic performance of S. birrea can be acclimated to a new environment.