The Physiology and Stability of Leaf Carbon Isotope Discrimination as a Measure of Water‐Use Efficiency in Barley on the Canadian Prairies

Temporal and seasonal water deficit is one of the major factors limiting crop yield on the Canadian prairie. Selection for low carbon isotope discrimination (Δ¹³C) or high water‐use efficiency (WUE) can lead to improved yield in some environments. To understand better the physiology and WUE of barley under drought conditions on the Canadian prairie, 12 barley (Hordeum vulgare L.) genotypes with contrasting levels of leaf Δ¹³C were investigated for performance stability across locations and years in Alberta, Canada. Four of those genotypes (‘CDC Cowboy’, ‘Niobe’, ‘170011’ and ‘Kasota’) were also grown in the greenhouse under well‐watered and water‐deficit conditions to examine genotypic variations in leaf Δ¹³C, WUE, gas exchange parameters and specific leaf area (SLA). The water‐deficit treatment was imposed at the jointing stage for 10 days followed by re‐watering to pre‐deficit level. Genotypic ranking in leaf Δ¹³C was highly consistent, with ‘170011’, ‘CDC Cowboy’ and ‘W89001002003’ being the lowest and ‘Kasota’‘160049’ and ‘H93174006’ being the highest leaf Δ¹³C. Under field and greenhouse (well‐watered) conditions, leaf Δ¹³C was significantly correlated with stomatal conductance (g_s). Water deficit significantly increased WUE, with ‘CDC Cowboy’– a low leaf Δ¹³C genotype with significantly higher WUE and lower percentage decline in assimilation rate (A) and g_s than the other three genotypes (‘Niobe’, ‘170011’ and ‘Kasota’). We conclude that leaf Δ¹³C is a stable trait in the genotypes evaluated. Low leaf Δ¹³C of ‘CDC Cowboy’ was achieved by maintaining a high A and a low g_s, with comparable biomass and grain yield to genotypes showing a high g_s under field conditions; hence, selection for a low leaf Δ¹³C genotype such as ‘CDC Cowboy’ maybe important for maintaining productivity and yield stability under water‐limited conditions on the Canadian prairie.     

The variation of relative water content,SPAD chlorophyll meter reading,stomatal conductance,leaf area,and specific leaf area of Jerusalem artichoke genotypes under different durations of terminal drought in tropical region

This work assessed the responses of Jerusalem artichoke (JA) genotypes experienced to different durations of terminal drought for relative water content (RWC), SPAD chlorophyll meter reading (SCMR), stomatal conductance (SC), leaf area (LA) and specific leaf area (SLA), investigated the significant contributor of physiological traits to yield and yield reduction and diversity of physiological traits in terminal drought tolerance genotypes. Field research was conducted during the late-rainy season for 2 years using a split-plot design with four replications. The three irrigation treatments involved no-drought (SD0), short (SD1) and long (SD2) durations of terminal drought were arranged as main plots, and sub-plots were six genotypes of JA. The current study revealed that RWC, SC, LA, and SLA, were drastically reduced whilst SCMR values slightly increased under SD1 and SD2 compared to SD0. According to multiple linear regression indicated that SLA (SD0), and RWC (SD1 and SD2) had high contributions to tuber fresh weight (TFW), whereas SC had a high contribution to TFW reduction under terminal drought. Principal component analysis also confirmed that the diversity of LA, RWC, and SLA had maximized contributing traits, followed by HI, SCMR and SC in these breeding materials of JA under three irrigation treatments. Our finding emphasized that JA125 (low SLA), HEL256 and JA37 (high SLA) lead to the high performance of TFW under SD0, and they exhibited high TFW under SD1 by performing medium RWC. Likewise, JA4 and JA37 had high TFW under SD2 caused by medium RWC. HEL253 and JA60 were identified as terminal drought-tolerant genotypes because of performed medium SC, which contributed to a low reduction in TFW. Our promising results are the basis for further studies, SLA, RWC and SC are an important keys for screening drought tolerance (low economic yield reduction) and these genotypes studied could be used for parental lines to improved drought tolerance progenies through breeding programs under different durations of terminal drought-prone areas.     

水分和CO2浓度对冬小麦气孔特征、气体交换参数和生物量的影响

利用可精准控制CO₂浓度([CO₂])的大型人工气候室, 研究了水分亏缺和[CO₂]升高对冬小麦气孔特征、气体交换参数及生物量的影响。结果表明, 水分亏缺导致冬小麦气孔开度减小和气孔空间分布的规则程度降低, 提高[CO₂]能够减缓水分亏缺时气孔开度和气孔分布规则程度的下降幅度。与充分灌溉相比, 不同水分亏缺条件下冬小麦的净光合速率、气孔导度和蒸腾速率均显著降低(P<0.05), [CO₂]仅可缓解轻度亏水对气体交换过程的影响, 该缓解能力随水分亏缺程度的加剧而降低。水分亏缺降低冬小麦生物量, 但[CO₂]升高对水分亏缺时生物量产生的影响不显著(P>0.05)。水分亏缺条件下, 冬小麦通过调整气孔开度和气孔空间分布格局改变叶片的气体交换效率, [CO₂]升高对冬小麦产生的“施肥效应”受土壤水分条件的限制。     

Antioxidant and Photosynthetic Responses of Cotton to Soil Drought Stress during Flowering and Fruiting Stage

[Objective] The purpose of this study was to examine potential drought tolerance mechanisms in cotton (Gossypium hirsutum L.). Biochemical (antioxidant, protein and compatible osmolyte) and physiological (photosynthesis) responses to drought stress during the flowering and fruiting stages were examined. [Method] Using two cotton genotypes (A001 and A705) with different drought tolerance, a pot study was conducted in 2016 with treatments consisting of control (well-watered) and water stress. Water stress treatment was designed as withholding water from the pots until stomatal closure followed by limited water supply for 25 days where water-stressed plants received 40% of the optimum quantity of water. Measurements were made on soluble protein, proline and malonaldehyde (MDA) concentrations, peroxidase (POD) activity and photosynthetic characteristics (net photosynthetic rate P_n, transpiration rate E, stomatal conductance G_s) during the period of water stress. [Result] The soluble protein concentration was decreased and POD activity and MDA level were increased in the leaf subtending cotton boll of A001 under water deficit when compared with the control, but no response was observed in A705. Proline level responded to water deficit inconsistently between the two genotypes and across all sampling dates. Water stress significantly decreased P_n, E and G_s in the main stem leaves for both A001 and A705. [Conclusion] The results indicated that POD, soluble protein and MDA are involved in A001 and A705 responses to water deficit, and A705 is more tolerant to soil drought than A001.     

高丹草水分利用效率与叶片生理特性的关系

在不同土壤供水条件下,研究了高丹草水分利用效率（WUE）与叶片光合速率（P_n）、蒸腾速率（T_r）、气孔导度（G_s）、叶温（T_l）、叶片相对含水量（RWC）的关系。结果表明,WUE随RWC、P_n呈二次曲线变化,P_n在27 µmol CO₂ m^-2 s^-1时,WUE值最大 (8.7 µmol CO₂ mmol^-1 H₂O);Tr在3.5~4 mmol H₂O m^-2 s^-1时WUE达最大值(8.4 µmol CO₂ mmol^-1 H₂O);Pn与Tr的非线性关系可以用抛物线方程表述,其中P_n最高时的Tr为临界值,超出该值即为奢侈蒸腾。G_s在0.4 molH₂O m^-2 s^-1时,WUE达到峰值8.39 µmol CO₂ mmol^-1 H₂O。实施提高气孔阻力并抑制蒸腾的措施,既节约水分,又促进光合作用,增加产量。P_n和T_r随温度的增加而增加,在35~36℃时P_n达最高值,表明在一定温度范围内,温度升高对提高WUE有利。WUE随RWC的升高而上升,RWC在84%~86%时WUE最大。适量增施氮肥,可提高Pn和Gs,进而提高WUE。     

Thresholds for leaf expansion and transpiration response to soil water deficit in a range of sunflower genotypes

The sunflower (Helianthus annuus L.) crop in southern Europe suffers from intense and frequent periods of water deficit. Minimisation of water loss in response to water deficit is a major aspect of drought tolerance and can be achieved through the lowering of either leaf area expansion rate or transpiration per unit leaf area (stomatal conductance). During three greenhouse pot experiments, leaf expansion (LE) and transpiration (TR) rates were monitored as the soil dried progressively for about 15 days. This study aimed to quantify the response of these two physiological processes to water deficit, expressed as the fraction of transpirable soil water (FTSW): response thresholds (onset of decline) were estimated on 25 sunflower genotypes from different generations of selection history. From these relationships, the thresholds below which LE and TR started to decrease from the control were calculated: little change was observed until FTSW was close to 0.6 for leaf expansion and 0.4 for daily transpiration. Variability in the response of all genotypes for expansion and transpiration control was better described using specific thresholds for each genotype rather than generic thresholds for sunflower. The ranking of genotypes was found to be unaffected for transpiration rate control, but this was not the case for leaf expansion. Identified response thresholds were not mutually correlated, suggesting that sunflower controls leaf expansion and transpiration rate independently. Neither was correlated with the release date of the genotype, suggesting that these traits were not subject to selection within evaluation environments.     

大气CO_2倍增条件下冬小麦气体交换对高温干旱及复水过程的响应

探究大气CO_2浓度倍增条件下冬小麦气体交换参数对高温干旱及复水过程的生理响应机制,有助于提高生态过程模型的模拟精度,更加准确地预测全球气候变化对农田生态系统初级生产力及其生态服务功能的影响。利用4个可精准控制CO_2浓度和温度的大型人工气候室,研究了CO_2浓度倍增条件下高温干旱及复水过程对冬小麦气孔特征和气体交换参数的影响。结果表明, CO_2浓度倍增(E)导致冬小麦远轴面气孔密度增加、气孔宽度减小、气孔空间分布规则程度降低,但提高叶片的净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)和水分利用效率(WUE)。高温干旱(HD)使叶片气孔长度、密度、周长和面积减小,导致叶片气体交换参数均显著下降。然而,高CO_2浓度及高温干旱(EHD)导致气体交换参数下降幅度相对较小,表明高CO_2浓度对高温干旱具有一定的缓解作用。此外,干旱复水后,不同处理条件下冬小麦叶片气体交换参数均有所升高,但高温干旱下叶片的气体交换参数仍未能恢复到对照水平,暗示光合器官可能在高温干旱时遭到损伤和破坏。     

Relationships between leaf morpho‐anatomy,water status and cell membrane stability in leaves of wheat seedlings subjected to severe soil drought

The impact of the genotype‐specific leaf morphological and anatomical characteristics on the ability of wheat plants to preserve leaf water balance and cell membranes stability under drought stress was investigated. Seedlings of six modern semi‐dwarf (carriers of Rht, Reduced height genes) and six old tall bread wheat varieties were subjected to soil drought by withholding watering for 6 days. Morpho‐anatomical traits (leaf area, perimeter, thickness, stomata and trichome density) of daily watered (control) plants were characterized by light microscopy, scanning and image analyses. The leaf water status in both control and stressed plants was determined by measuring the relative water content (RWC). The leaf cell membranes stability in stressed plants was estimated by conductometric determination of the membranes injury index. On average, the modern semi‐dwarf varieties had less leaf area and leaf perimeter, and less dissection index, a parameter characterizing the leaf shape. Under drought stress, the modern genotypes maintained better water balance evidenced by significantly higher leaf RWC and better‐preserved the cell membranes stability supported by significantly lower Injury index. The correlations between morpho‐anatomical traits in control plants and drought tolerance‐related traits showed that the higher the leaf dissection index (i.e. more oblong leaves), the greater the water loss and the leaf membrane damages after desiccation were. The effect of shape of the evaporating surface on the water loss was modelled using wet filter paper. Similar to plant leaves, the evaporation and, respectively, water loss from paper pieces of more oblong shape (i.e. higher dissection index) was more intensive. The elucidation of the impact of the leaf shape on transpiration might contribute to better understanding of the mechanisms used by plants to maintain water reserves during drought stress and could be a basis for developing of simple and fast screening methods aiding the selection of drought tolerant genotypes.     

Reproductive response of two morphologically different pea cultivars to drought

Water use by semi-leafless peas (Pisum sativum L.) is usually less than that of conventional peas because of their reduced surface leaf area, suggesting that semi-leafless peas would be less sensitive to drought because drought develops later. This work aimed to study the reproductive response of peas cv. Solara (semi-leafless) and cv. Frilene (conventional) subjected to similar controlled soil drought during the critical period occurring between flowering and initial seed filling. Plants were subjected to drought by watering with a fraction of water used in the evapotranspiration of control plants. Soil, pod and seed water contents, leaf water status parameters, dry matter (DM) partitioning, seed yield, yield components and water use efficiency (WUE) were measured. Although soil water content decreased in a similar way in both cultivars, leaf Ψ_w and RWC only decreased significantly in Solara. Well-watered Frilene plants produced higher shoot and pod DM, but lower seed DM. Well-watered Solara plants produced lower pod DM and higher seed DM than Frilene. Under drought, Frilene increased partitioning of total plant DM to vegetative organs, particularly roots, and decreased DM allocation to pods and seeds increasing flower abortion. By contrast, droughted Solara interrupted vegetative growth and increased leaf senescence but maintained similar partitioning of total plant DM to pods and seeds as in well-watered conditions. For both cultivars there was a close relationship between the percentage of total DM partitioned into seeds and WUE_y (water use efficiency on seed yield basis). Results demonstrate that when plants suffered the same level of drought in the soil, the reproductive response of the two cultivars was linked to differences in their WUE.     

探讨品种间差异改良作物水分利用效率

提高水分利用效率是缓解水资源危机实现作物可持续生产的重要策略。本文对叶片尺度的瞬时WUE和单株尺度WUE的品种间差异,瞬时WUE到田间尺度WUE的尺度转换,以及瞬时WUE与产量之间的关系进行了讨论。瞬时WUE具有较大的遗传变异性,在亏水条件下品种间差异更显著。在禾谷类作物上,气孔导度与瞬时WUE密切相关。单株尺度WUE在亏水条件下品种间差异显著,足水条件下差异相对较小。气孔导度是影响单株尺度WUE的重要性状,品种之间气孔对水分亏缺的敏感性差异较大。瞬时WUE向田间尺度WUE的尺度转换不仅受到冠层阻力和边界层阻力的制约,还受土壤蒸发与作物蒸腾比率以及同化物分配模式的影响。瞬时WUE与产量的关系决定于环境的水分条件,在作物生长发育主要依靠土壤中储存水分的干旱条件下,瞬时WUE高对获得高产有利。相反,在水分条件较适宜的地区,高瞬时WUE性状不利于高产。     

Leaf Carbon Isotope Discrimination as an Accurate Indicator of Water‐Use Efficiency in Sunflower Genotypes Subjected to Five Stable Soil Water Contents

Leaf carbon isotope discrimination (CID) has been suggested as an indirect tool for breeding for water‐use efficiency (WUE) in various crops. This work focused on assessing phenotypic correlations between WUE and leaf CID and analysing genotypic variability in four sunflower genotypes grown in a greenhouse in pots with five different stable levels of soil water content (SWC). We measured WUE at whole plant and leaf (intrinsic) level. At whole plant level, WUE was derived from the ratio of total dry aerial biomass (BM) to cumulative water transpired (CWT). At leaf level, intrinsic WUE was calculated as the ratio of light‐saturated CO₂ assimilation to stomatal conductance (A/g_s) in younger expanded leaves. Significant differences among the four genotypes and the five SWCs were observed for whole plant and leaf WUE and CID. Strong negative correlations were observed between whole plant WUE and CID as well as between intrinsic WUE and CID with decreasing water availability. No relationships appeared between BM production and WUE or CID. Our results can help agronomists and breeders to evaluate sunflower lines with high WUE for adaptation to drought conditions and for reducing water consumption and crop water needs. Leaf CID appears to be a pertinent and valuable trait to select sunflower genotypes with high WUE.     

移植和钾肥对降香黄檀(Dalbergia odorifera)比叶面积和水分利用效率的影响

为了解降香黄檀叶片性状和水分利用效率(water use efficiency,WUE)对移植和钾肥两种抚育措施的响应,以中幼龄降香黄檀为研究对象开展了移植和钾肥两组试验,测定了比叶面积(specificleafarea,SLA)、WUE及相关因子。结果显示:移植各处理中去半冠不移叶干重最大为0.0613 g,断根不移叶干重最低为0.0487 g,去半冠不移叶面积最大为12.072 cm2;SLA的大小顺序为断根不移>去半冠不移>去半冠移植>CK>全冠移植。随着钾肥用量的增加叶干重、叶面积、SLA均呈增大趋势。在光强为1800μmol·m-2·s-1下,各处理中全冠移的净光合速率(net photosynthetic rate,Pn)高于去半冠不移、去半冠移植和断根不移;蒸腾速率(transpiration rate,Tr)最大的为断根不移;WUE的大小顺序为全冠移植>CK>去半冠移植>去半冠不移>断根不移。WUE随钾肥用量的增加逐渐降低。移植和钾肥处理降香黄檀叶片的SLA、WUE均表现出显著的负相关关系。不同培育措施下,降香黄檀通过改变叶片形态,使SLA和WUE形成相反的趋势,反映了其适应光照、土壤等各种因素的资源利用策略和光合产物累积模式。本研究结果为人工培育降香黄檀提供一定的理论依据。     

玉米水分利用效率、碳稳定同位素判别值和叶面积之间的关系

通过盆栽试验,研究了水分胁迫对玉米各生育期叶面积(LA)、比叶面积(SLA)、水分利用效率(WUE)和碳稳定同位素判别值(Δ¹³C)的影响以及不同水分条件下WUE、茎叶Δ¹³C和SLA之间的关系。试验设4个水分处理, 分别为田间持水量的75%~100%(W1)、50%~75%(W2)、30%~50%(W3)和0~30%(W4)。W2和W3处理对生物量干重的影响在玉米拔节期明显,而W4处理导致各生育期生物量干重的极大降低。在W2和W3处理下,玉米各生育期的WUE随着水分胁迫程度的增加而增加;而W4处理下,WUE在孕穗期后则显著降低。SLA在孕穗期达到最大。玉米各生育期叶片Δ¹³C在W1、W2和W3处理中呈随水分胁迫的增加而降低的趋势,而W4处理下的叶片Δ¹³C则高于W2和W3处理。玉米叶片光合同化物质往茎秆转移时没有发生碳同位素的分馏作用。在玉米的各生育期,叶片Δ¹³C、茎秆Δ¹³C和玉米WUE呈一致性的负相关;各生育期的SLA与Δ¹³C呈正相关关系,而与WUE呈显著的负相关。     

The effect of nitrate nutrition on iron chlorosis and leaf growth in sunflower (Helianthus annuus L.)

The objective of this work was to investigate the effects of nutrient solution pH, nitrogen form (NO₃, NH₄NO₃), bicarbonate and different Fe concentrations in the nutrient solution on the Fe concentration in roots and on the development of Fe deficiency symptoms in sunflower plants (Helianthus annuus L.). High pH in the nutrient solution induced by nitrate supply or by a pH-stat device led to increased Fe concentrations in roots and low leaf Fe concentrations associated with a significant decrease in leaf chlorophyll concentration manifested by yellow leaves. Plants of the nitrate fed treatments with 1 μM Fe in the nutrient solution were also characterized by reduced leaf growth and by the suppression of new leaf formation. The reduced leaf growth and the suppression of new leaves only occurred with nitrate and not with NH₄NO₃ in all treatments with 1 μM Fe in the nutrient solution. All symptoms were removed by a high Fe concentration in the nutrient solution (100 μM) at low external pH proving that suppression of leaf formation, reduced leaf growth and low chlorophyll concentration were caused by Fe deficiency. In the nitrate treatment with a low Fe supply (1 μM Fe) and pH 4 in the nutrient solution leaf chlorophyll concentrations similar to the controls were found. In comparison to control plants (NH₄NO₃, 1 μM Fe), leaf growth was still significantly reduced, and new leaf formation was suppressed. The chlorophyll concentration and CO₂ assimilation rate did not differ from those of the control plants. These results show that Fe deficiency is also characterized by small green leaves and the suppression of leaf formation. At the onset of leaf development, leaf growth and new leaf formation may respond more sensitively to poor Fe efficiency than chlorophyll concentration. In experiments with NO₃ plus HCO₃, simulating soil solution conditions prevailing in calcareous soils, the Fe efficiency of the youngest leaves was poor, showing retarded leaf growth and low chlorophyll concentration.     

Compensatory Growth Responses During Reproductive Phase of Cowpea after Relief of Water Stress

Unpredictable drought affects growth and yield of dryland cowpea ( Vigna unguiculata [L.] Walp.) during rainy season. With the objective of identifying compensatory growth responses after relief of water stress, pot-grown plants (cv. C-752) were water-stressed at flowering, and physiological responses, short term dry matter partitioning upon relief of water stress, and productivity at maturity were studied. Water stress decreased, to varying degrees, leaf water potential, stomatal conductance, photosynthesis rate and transpiration rate. Recovery in assimilation lagged behind that in water relations. Assimilate supply seemed to be limiting early pod growth upon relief of water stress due to low photosynthesis rate, reduced leaf area per pod, and increased partitioning to leaf expansion. However, later pod growth was not limited by assimilate supply and final dry matter per pod was similar in both non-stressed and stress-affected plant. Cowpea exhibited the following growth responses during pod-fill stage upon relief of water stress: 1. increase in leaf area, 2. shift in dry matter partitioning in favour of leaf expansion, 3. extended green leaf duration, and 4. increase in pod number. These partially compensating physiological responses probably ensure reasonable productivity of dryland cowpea during rainy season.     

Influence of Soil Moisture on Growth, Water Use and Yield of Mustard

A field experiment was conducted to study the influence of soil moisture on growth, water use and yield of mustard ( Brassica juncea L. cv. Rai 5 ). Two soil moisture regimes were rainfed and irrigated at 10 days interval throughout the growing season. The total amount of water received as irrigation was 110 mm and as rainfall was 15 mm. Total dry matter per unit ground area, leaf area index (LAI), crop growth rate (CGR) and net assimilation rate (NAR) were increased and leaf area ratio (LAR) and specific leaf area (SLA) were decreased by irrigation. Chlorophyll content and relative leaf water content (RLWC) were increased by irrigation, but proline content was greater in the rainfed crop at both the flowering and pod-filling stages. Time taken to first flowering, duration of flowering, number of seeds/pod and harvest index were unaffected by irrigation. Plant height at harvest, number of pods/plant, seed yield and oil content of seeds were increased and 1000-seed weight was decreased by irrigation. The consumptive use of water increased with an increase in water supply, but the water use efficiency (WUE) was decreased.     

Growth analyses of tomato genotypes grown under low night temperatures and low light intensity

Summary In three experiments the growth of 16 genotypes of tomato was examined. The plants were raised in growth rooms at a day temperature of 19°C and night temperatures of 14, 10 or 6°C respectively under a light intensity of 24 Wm^-2 visible radiation and a daylength of 8 hours. The results were analysed by a multivariate analysis of variance.Relative growth rate (RGR), leaf area ratio (LAR), specific leaf area (SLA) and leaf weight ratio (LWR) decreased with time. The change in net assimilation rate (NAR) was small. The decrease in RGR was mainly due to the decrease in LAR.RGR, LAR and SLA were lower and LWR slightly higher at lower night temperatures. NAR was hardly affected. The lower RGR at lower night temperatures was mainly due to a lower SLA.Significant differences between genotypes were found in total dry weight, NAR, LAR, SLA and LWR, but hardly in RGR. Significant genotype × temperature interactions occurred.LAR and SLA were positively, NAR and LAR, and NAR and SLA negatively correlated.     

气象因子与梨叶片水分亏缺的相关分析

对气象因子与梨叶片水分亏缺的研究结果表明，相对湿度对梨树各类枝叶片水分亏缺均呈显著或极显著的负相关关系。通径分析证实了湿度、温度的影响，肯定了气压对短枝叶片水分亏缺的影响。多元线性逐步回归分析与通径分析的结果完全一致，梨叶片水分亏缺的日变动态和季变动态的分析结果表明，在梨的生长季节前后期注意灌水对于减少水分亏缺，提高光合强度，增加产量具有现实意义。     

Genotypic Variability in Drought Performance and Recovery in Cowpea under Controlled Environment

Mid‐season drought is a factor frequently limiting crop production in the moist to dry savannah zones of the tropical and subtropical regions of the world. Ten cowpea genotypes were subjected to a cycle of drought at flowering followed by re‐watering to study variation in drought performance and recovery. Drought caused a reduction in leaf assimilation rate, transpiration rate and stomatal conductance with genotypic variances of 75.4, 57.9, and 83.3 %, respectively. Only genotypic variance in stomatal conductance increased appreciably under drought. Reductions in leaf water potential as a consequence of drought positively correlated with a decline in assimilation rate, which was associated with stomatal closure. One week after re‐watering, the three gas exchange parameters of stressed plants recovered fully and attained values 10–30 % higher than the well‐watered plants with increased genotypic variability. Reductions in the total dry matter during the drought interval varied from 11 to 50 % among genotypes, but were of minor importance for the total dry matter at maturity. After stress, the gain in dry matter varied considerably among the stressed genotypes, with stressed plants showing higher gain than the unstressed plants during this interval. This was associated with increased availability of assimilates due to enhanced green leaf area duration after stress release. Variability in drought recovery among genotypes was found, and appears to be more important for final yield than responses during drought.     

陇中半干旱区马铃薯集雨限灌效应研究

采用大田试验与实验室分析相结合的方法,研究了集雨限灌对旱作马铃薯田蒸散量、灌水利用率、产量、产量性状及薯块品质的影响。结果表明,集雨限灌45 mm条件下马铃薯水分利用效率(WUE)显著提高,在此基础上增加灌水量,WUE降低;苗期限灌处理的WUE和灌水利用效率(IWUE)均高于薯块膨大期;苗期限灌45 mm处理综合用水效率较高。限灌可提高旱作马铃薯产量、大薯率与中薯率,降低小薯率,苗期限灌有利于大薯率的提高,薯块膨大期限灌有利于中薯率的提高;限灌降低马铃薯单株结薯数,可提高单株薯产量;超过45 mm随限灌量的增加,产量增加不显著,绿薯率和烂熟率显著增加。限灌能降低马铃薯薯块淀粉含量,提高薯块蛋白质含量。苗期限灌45 mm为半干旱区马铃薯最佳集雨限灌模式。