两种南亚热带林下灌木叶片水分特性的比较研究

鼎湖山南亚热带针叶—阔叶混交林下灌木桃金娘和三叉苦叶片气孔导度的日进程多为单峰形。一天中出现气孔导度高值的时间随季节而异,从3月到10月逐渐提前。夏季气孔导度最大,冬季最小。8月份生长于坡顶群落中的两种灌木叶片气孔出现“午睡”现象。不同生长地点中,桃金娘的气孔导度均明显高于三叉苦。叶片水势从早晨起逐渐降低,中午达最低值,随后有所回升。 3月和8月的水势较高,12月水势最低。水势与气孔导度间呈双曲线关系。压力—体积曲线的测定表明叶片水势低值时仍能维持正膨压。     

豆科复叶和单叶树种的光合-水分关系分析北大核心CSCD

以豆科(Fabaceae)11个复叶树种和6个单叶树种为材料,测定他们的气孔导度、叶片水力导度、水势、相对含水量等指标,分析叶型对枝叶光合水分关系的影响。结果显示,复叶树种正午叶轴水势(-0.91MPa)与单叶树种正午枝条水势(-0.88MPa)间无显著差异,但正午枝条水势(-0.60MPa)显著高于单叶树种。复叶树种正午气孔导度降低的百分比(55.3%)显著高于单叶树种(34.1%)。叶片、叶轴和枝条正午水势两两之间均显著正相关,但与正午气孔导度之间均不存在相关性。本研究中,17个树种的正午叶片水力导度与气孔导度间显著正相关(r=0.79,P<0.001),但他们与气孔导度降低百分比间呈负相关(r=-0.81,P<0.001),说明叶片导水率对日间气孔导度的维持具有重要作用。研究结果表明单叶和复叶树种在光合水分关系上存在明显差异,说明他们对环境条件具有不同的适应策略。     

豆科复叶和单叶树种的光合-水分关系分析

以豆科（Fabaceae）11个复叶树种和6个单叶树种为材料,测定他们的气孔导度、叶片水力导度、水势、相对含水量等指标,分析叶型对枝叶光合水分关系的影响。结果显示,复叶树种正午叶轴水势（-0.91 MPa）与单叶树种正午枝条水势（-0.88 MPa）间无显著差异,但正午枝条水势（-0.60 MPa）显著高于单叶树种。复叶树种正午气孔导度降低的百分比（55.3%）显著高于单叶树种（34.1%）。叶片、叶轴和枝条正午水势两两之间均显著正相关,但与正午气孔导度之间均不存在相关性。本研究中,17个树种的正午叶片水力导度与气孔导度间显著正相关（r=0.79,P<0.001）,但他们与气孔导度降低百分比间呈负相关（r=-0.81,P<0.001）,说明叶片导水率对日间气孔导度的维持具有重要作用。研究结果表明单叶和复叶树种在光合水分关系上存在明显差异,说明他们对环境条件具有不同的适应策略。     

成熟马占相思水力导度对水分利用和光合响应的季节性差异

通过测定成熟马占相思叶片的水势、气孔导度、蒸腾速率(Tr)、叶面积指数、边材面积等参数,研究了湿季(5月)和干季(11月)叶片的水力导度(K1)、水分和光合特性的关系.结果表明:高大植株(平均树高20 m、胸径0.26 m)的边材面积与叶面积的比率(Asp/Acl)比较小植株(平均树高14.5 m、胸径0.19m)高8.5％,前者的木质部水分通量大于后者,以支持冠层叶片的水分利用.对木质部易损曲线进行分析,K1降低50％时,湿、干季的叶片水势(Ψ1)分别为-1.41和-1.55 MPa,且干季的木质部空穴化的易损性高于湿季.湿、干季的K1峰值分别为5.5和4.5 mmol·m-2·s-1·MPa-1,最大蒸腾速率(Trmax)分别为3.6和1.8 mmol·m-2·s-1,且湿季的K1和Trmax明显大于干季.一天中K1和Tr的多次波动反映了木质部空穴化和修复的往复循环,叶片气孔在K降低超过50％或Ψ1达到-1.6MPa时关闭,气孔导度在K1达到50％前仍保持较高水平.干季的水力导度与光合速率的相关性较湿季明显.季节更迭导致叶片水力导度损失是Tr和CO2交换下降的原因.     

羊草叶片气孔导度特征及数值模拟

对松嫩平原草地羊草叶片气孔导特征及与环境因子关系的研究结果表明,羊草叶片气孔导度日变化与环境因子密切相关,晴天表现为双峰曲线,阴天为单峰曲线,同时叶片气孔导度（gs)对瞬时光合有效辐射（PAR）,叶片与空气间的水汽压亏损（VPD）,空气温度（Ta）反应十分明显,依据野外实测资料,在对国际上两类代表性气孔导度模型验证比较的基础上,建立了适用于羊草草原的羊草叶片气孔导度对环境因子的响应模型gs=PAR(2.01Ta^2 147.74Ta-2321.11)/(444.62 PAR)(-538.04 VPD).     

长白山阔叶红松林叶片气孔导度与环境因子的关系

通过对阔叶红松林主要树种叶片的野外测定,研究了长白山阔叶红松林叶片气孔导度对环境因子的响应,结果表明,阔叶红松林叶片的气孔导度与瞬时光合有效辐射（PAR）和温度（Ta）呈正相关,而与水汽压亏损（PVD）呈负相关。对气孔导度模型的验证表明：Jarvis的非线性模型比Ball的线性模型更适于阔叶红松林叶片的气孔导度模拟。长白山阔叶红松林叶片的气孔导度对环境因子的响应模型为：gs=PAR（1.606T2a＋118.19Ta-1878.67）/（355.70＋PAR）（-430.433＋VPD）。此模型有助于进一步估算叶片光合作用,通过尺度化模拟阔叶红松林群落生产力以及土壤-植物-大气系统之间的水热交换奠定了基础。     

豆科复叶和单叶树种的光合-水分关系分析

以豆科(Fabaceae) 11个复叶树种和6个单叶树种为材料,测定他们的气孔导度、叶片水力导度、水势、相对含水量等指标,分析叶型对枝叶光合水分关系的影响。结果显示,复叶树种正午叶轴水势(-0. 91 MPa)与单叶树种正午枝条水势(-0.88 MPa)间无显著差异,但正午枝条水势(-0.60 MPa)显著高于单叶树种。复叶树种正午气孔导度降低的百分比(55.3%)显著高于单叶树种(34.1%)。叶片、叶轴和枝条正午水势两两之间均显著正相关,但与正午气孔导度之间均不存在相关性。本研究中,17个树种的正午叶片水力导度与气孔导度间显著正相关(r=0.79,P 0.001),但他们与气孔导度降低百分比间呈负相关(r=-0.81,P 0. 001),说明叶片导水率对日间气孔导度的维持具有重要作用。研究结果表明单叶和复叶树种在光合水分关系上存在明显差异,说明他们对环境条件具有不同的适应策略。     

荷木整树蒸腾对干湿季土壤水分的水力响应

降雨在时间上的非均匀分配导致森林土壤含水量呈现明显的干、湿季变化,并可能在干季形成水分胁迫,引起植物蒸腾变化。在监测环境因子的同时,利用Granier热消散探针连续监测荷木(Schima superba)的树干液流,以液流密度值计算整树蒸腾,并结合水力导度与叶片/土壤的水势差,探讨环境因子和水力导度对荷木整树蒸腾的协同控制。结果表明,华南地区的季节性降雨形成的干、湿季并未引起荷木蒸腾在季节上的显著差异,但对产生蒸腾的水力生理产生了显著影响。荷木蒸腾在干、湿季均与主要驱动环境因子(光合有效辐射PAR和水汽压亏缺VPD)呈显著正相关。在水热充足的湿季,荷木蒸腾主要受气孔导度调节;在干季,当空气水汽压亏缺达2.132 MPa时,水力导度与气孔导度协同控制蒸腾。整树水力导度对整树蒸腾的水力补偿出现在15:00—17:00,平均补偿值为0.08 g/s。利用蒸腾的估测值与实测值之间的差值量化荷木的水力补偿效应,是对水力导度与气孔导度协同控制树木蒸腾机理的深入探索。研究结果对于掌握季节性降雨不均背景下华南地区主要造林树种需水和耗水规律,有效发挥森林保水功能具有重要意义。     

干旱和复水对膜下滴灌棉花根系及叶片内源激素含量的影响

新疆气候生态条件下,采用膜下滴灌技术,在棉花不同生育时期设置不同程度干旱处理,研究干旱和复水对棉花根系及叶片内源激素含量和叶片气孔导度的影响.结果表明:在不同生育阶段,随土壤含水率的降低,根系及叶片脱落酸(ABA)含量显著增加,玉米素(ZRs)含量减少,叶片气孔导度(gs)和光合速率(Pn)显著降低,以初花-盛花期土壤相对含水率为40％ ～ 45％处理降幅较大.土壤干旱处理结束后复水,根系及叶片ABA含量并未随土壤水分条件的改善而降低,根系ZRs含量在复水后1～3d均可恢复或超过对照,与叶片gs呈正相关,其中以盛蕾-初花期土壤相对含水率为50％～55％处理棉株叶片ZRs含量和gs恢复速度快、强度大.说明干旱后复水根系较高的ZRs含量是导致其叶片gs和Pn较高的主要原因.     

在高CO2浓度下四种亚热带幼树光合作用对水分胁迫的响应

在较高CO2浓度(700μl/L)下,随着光强(PAR)增高,来自高林密度林地植物罗伞的光合速率(Pn)增高,当叶片水势(Ψ)从-0.92kPa降低至-2.0kPa,Pn/PAR斜率从0.037降至0.017,即表观量子产率(αA)降低54.0%;而来自林密度中等林地的九节和荷木,当叶片水势分别从-0.80kPa降至-2.00和-1.20kPa,αA分别降低22.2%和19.4%;来自开阔林地的桃金娘叶片水势降低时,αA亦见明显降低.当叶片水势降低1kPa,罗伞叶片的光能转换效率(δ)降低0.10电子/量子或39.2%,九节和荷木,以及桃金娘相应降低0.033至0.05电子/量子.来自高林密度林地罗伞叶片水势从-0.92kPa降低至-2.00kPa,最大羧化速率(Vcmax)降低24.3%,来自林密度中等林地的九节叶片水势低1kPa,Vcmax降低7.08μmol/m2s,荷木和疏林桃金娘则有明显高的Vcmax.叶片水势降低,Vcmax亦受明显抑制(P＜0.01).结果表明,来自林密度中等林地的荷木和来自开阔林地的桃金娘有着高的Rubisco激活特性,叶片水势降低明显影响Rubisco的激活特性.来自较稀疏林地的荷木和桃金娘有较高电子传递速率(J),叶片水势降低1kPa,J分别降低52.5和58.1μmolm2/s,而来自高林密度林地的罗伞,J降低仅为8.9～9.0μmolm2/s.表明阳生树种的J对水分胁迫响应敏感.研究结果表明,阳生树种有较高的Vcmax,J,δ和Γ*.叶片水势降低引起光合参数不同程度降低,但阳生树种仍维持较高的光合参数值,这有利于阳生植物生物量的积累和保持种群的优势,从而有利于亚热带常绿阔叶林阳生植物群落向中生性和耐荫顶极植物群落的演替.     

北京山区侧柏林冠层-大气蒸腾导度模拟及环境因子响应

蒸腾导度模型是衡量冠层-大气界面水汽输出的重要阻力模型,研究其特征及对环境因子的响应,为揭示森林冠层-大气界面水汽输出阻力机制提供理论依据。以首都圈森林生态系统定位观测研究站侧柏林为研究对象,采用TDP热探针法测定侧柏林树干液流密度,同步监测光合有效辐射、饱和水汽压差、气温、风速等主要环境因子,分析冠层导度和空气动力学导度的动态变化,构建冠层-大气蒸腾导度模型并模拟,明确冠层-大气蒸腾导度对各环境因子的响应关系。结果表明:蒸腾导度季节变化表现为非生长季与冠层导度趋势一致,生长季与空气动力学导度趋势一致,全年均为单峰趋势。冬季蒸腾导度与冠层导度保持较稳定差值(45 mol m^(-2 )s^-1左右),其他季节蒸腾导度与冠层导度、空气动力学导度的最大差值,均在各季节冠层导度、空气动力学导度的峰值水平。全年日均蒸腾导度冬季最大(86.92 mol m^(-2 )s^-1),其他季节较小且稳定(40—50 mol m^(-2 )s^-1之间)。在非生长季各环境因子对蒸腾导度的影响与对冠层导度的影响基本一致,温度为主要影响因子(r=-0.198),其他环境因子影响较小(r<0.1);在生长季中风速为主要影响因子(r=0.488),光合有效辐射(r=0.228)和饱和水汽压差(r=-0.299)的影响明显升高,温度的影响降低(r=0.114)。蒸腾导度模型较好的模拟了冠层-大气界面侧柏蒸腾不同季节的变化规律,阐明了各环境因子和冠层导度、空气动力学导度对蒸腾导度的影响机制,证实在生长季应重视空气动力学导度对蒸腾的影响。     

Internal conductance does not scale with photosynthetic capacity: implications for carbon isotope discrimination and the economics of water and nitrogen use in photosynthesis

Central paradigms of ecophysiology are that there are recognizable and even explicit and predictable patterns among species, genera, and life forms in the economics of water and nitrogen use in photosynthesis and in carbon isotope discrimination (delta). However most previous examinations have implicitly assumed an infinite internal conductance (gi) and/or that internal conductance scales with the biochemical capacity for photosynthesis. Examination of published data for 54 species and a detailed examination for three well-characterized species--Eucalyptus globulus, Pseudotsuga menziesii and Phaseolus vulgaris--show these assumptions to be incorrect. The reduction in concentration of CO2 between the substomatal cavity (Ci) and the site of carbon fixation (Cc) varies greatly among species. Photosynthesis does not scale perfectly with gi and there is a general trend for plants with low gi to have a larger draw-down from Ci to Cc, further confounding efforts to scale photosynthesis and other attributes with gi. Variation in the gi-photosynthesis relationship contributes to variation in photosynthetic 'use' efficiency of N (PNUE) and water (WUE). Delta is an information-rich signal, but for many species only about two-thirds of this information relates to A/gs with the remaining one-third related to A/gi. Using data for three well-studied species we demonstrate that at common WUE, delta may vary by up to 3 per thousand. This is as large or larger than is commonly reported in many interspecific comparisons of delta, and adds to previous warnings about simplistic interpretations of WUE based on delta. A priority for future research should be elucidation of relationships between gi and gs and how these vary in response to environmental conditions (e.g. soil water, leaf-to-air vapour pressure deficit, temperature) and among species.     

黄土高原苹果园蒸腾导度大气驱动规律比较

植物蒸腾导度是表征土壤-植物-大气连续体（SPAC）中植物-大气间水汽传导过程、反映植物水分调控能力的一类重要变量,常见有冠层导度（G_c）、冠层气孔导度（G_s）与叶片气孔导度（g_s）,明确三者在反映冠层蒸腾过程时的异同或关联性对于理解植物水分利用机制具有重要意义。本研究基于对黄土高原果园苹果树生长季内树干液流（J_s）及环境因子的连续观测,计算了G_c、G_s及脱耦联系数（Ω）等变量,并与短期连续观测的叶片气孔导度（g_s）比较,分析了G_c、G_s和g_s在反映冠层蒸腾特征方面的异同及其关系。结果表明,日变化过程中G_s、g_s呈"单峰"型曲线,而G_c则呈"先增后减,午后抬升"的"双峰"型曲线。g_s与G_s存在较紧密的线性关系（R²=0.80）,但与G_c的线性关系较弱（R²=0.02）。G_c、G_s均随大气水汽压亏缺（VPD）的变化呈现确定的规律,其中,上边界函数呈递减的对数函数关系,平均值则符合先增后减的Log-Normal函数关系（R²>0.95）,拐点对应的VPD值分别为1.33和1.16 kPa。在一日内,G_s对VPD变化的响应过程与g_s对VPDL （基于叶片温度计算的水汽压亏缺）变化的响应过程总体一致,其一致性高于G_c对VPD变化的响应。整个生长季（4-10月）中果树的Ω平均值为0.12,随着Ω递减,G_c与G_s的线性相关性愈趋紧密,其斜率呈递增趋势,G_c越来越趋近于G_s。研究结果表明,在北方地区,基于树干液流的监测能较准确的推导整株并估算林分的冠层蒸腾导度。与实测g_s的变化过程比较,G_s比G_c具有更高的一致性,G_s可以作为描述苹果树水分利用过程响应大气驱动的更为恰当的变量。     

Transpiration and whole-tree conductance in ponderosa pine trees of different heights

Changes in leaf physiology with tree age and size could alter forest growth, water yield, and carbon fluxes. We measured tree water flux (Q) for 14 ponderosa pine trees in two size classes (12 m tall and ∼40 years old, and 36 m tall and ∼ 290 years old) to determine if transpiration (E) and whole-tree conductance (g _t) differed between the two sizes of trees. For both size classes, E was approximately equal to Q measured 2 m above the ground: Q was most highly correlated with current, not lagged, water vapor pressure deficit, and night Q was <12% of total daily flux. E for days 165–195 and 240–260 averaged 0.97 mmol m^–2 (leaf area, projected) s^–1 for the 12-m trees and 0.57 mmol m^–2 (leaf area) s^–1 for the 36-m trees. When photosynthetically active radiation (I _P) exceeded the light saturation for photosynthesis in ponderosa pine (900 μmol m^–2 (ground) s^–1), differences in E were more pronounced: 2.4 mmol m^–2 (leaf area) s^–1 for the 12-m trees and 1.2 mmol m^–2 s^–1 for the 36-m trees, yielding g _t of 140 mmol m^–2 (leaf area) s^–1 for the 12-m trees and 72 mmol m^–2 s^–1 for the 36-m trees. Extrapolated to forests with leaf area index =1, the 36-m trees would transpire 117 mm between 1 June and 31 August compared to 170 mm for the 12-m trees, a difference of 15% of average annual precipitation. Lower g _t in the taller trees also likely lowers photosynthesis during the growing season. Received: 19 April 1999 / Accepted: 23 March 2000     

Photosynthesis affects following night leaf conductance in Vicia faba

Night-time stomatal opening in C₃ plants may result in significant water loss when no carbon gain is possible. The objective of this study was to determine if endogenous patterns of night-time stomatal opening, as reflected in leaf conductance, in Vicia faba are affected by photosynthetic conditions the previous day. Reducing photosynthesis with low light or low CO₂ resulted in reduced night-time stomatal opening the following night, irrespective of the effects on daytime stomatal conductance. Likewise, increasing photosynthesis with enriched CO₂ levels resulted in increased night-time stomatal opening the following night. Reduced night-time stomatal opening was not the result of an inability to regulate stomatal aperture as leaves with reduced night-time stomatal opening were capable of greater night-time opening when exposed to low CO₂. After acclimating plants to long or short days, it was found that night-time leaf conductance was greater in plants acclimated to short days, and associated with greater leaf starch and nitrate accumulation, both of which may affect night-time guard cell osmotic potential. Direct measurement of guard cell contents during endogenous night-time stomatal opening will help identify the mechanism of the effect of daytime photosynthesis on subsequent night-time stomatal regulation.     

Gas exchange in a 20-year-old stand of Scots pine

The rates of net photosynthesis and transpiration of one-year-old shoots were measured in situ in five different positions within the crown of a young Scots pine ( Pinus sylvestris L.). Measurements were carried out on south- and north-facing shoots on the third and sixth whorls, respectively, and on an east-facing shoot on the ninth whorl. In another investigation the rates of gas exchange of one-year-old shoots on the third whorl of eight different trees were studied. The measurements were made during June and July, 1977, under non-limiting conditions of soil water. The daily rates of net photosynthesis in whorls three and six followed the light conditions closely, with higher rates for the south side of each whorl and higher for whorl three than six. On whorl nine the shoot had a higher light compensation point and a low rate of photosynthesis at light saturation compared to the other shoot positions. The quantum yield for the shoot on the lowest whorl, as estimated from the linear part of the light response curve, was 50% lower than for shoots on whorl three and six.
The variation in transpiration rates was pronounced within the crown as an effect of differences in the absolute value and diurnal course of stomatal conductance. The variation in net photosynthesis was small between different trees while the variation in transpiration was much higher. Thus the variation in water use efficiency was great. It is concluded that it is possible to extrapolate measurements of net photosynthesis from individual trees up to a stand level without introducing large errors in the estimate. More caution must be paid before extrapolating tree transpiration up to stand transpiration. However, before an extrapolation of gas exchange is made from tree to stand level the variation in net photosynthesis and transpiration rate within the crown must be known.     

Activation of chloride conductance in pig jejunal brush border vesicles

Summary Requirements for the activation of Cl conductance have been investigated in pig jejunal brush border vesicles. The stability of ATP as a substrate for protein kinase activity, the stability of the phosphoprotein product of protein kinase action, and the choice of buffer system used for vesicle preparation were studied as variables which affected the outcome of in vitro activation attempts. Arsenate was selected as the most effective agent in protecting ATP from hydrolysis by the phosphatase activity in this vesicle system. Brush border vesicle protein appeared to prevent the accumulation of phosphoprotein in a cAMP-dependent protein kinase reaction, and vesicle protein only had phosphate acceptor activity when KF was added as a presumptive inhibitor of phosphoprotein phosphatase.A Cl conductance response to a potassium gradient and valinomycin was present in vesicles prepared in buffers containing tetramethylammonium. Cl^– conductance activity was not increased in this system by the addition of ATP, dibutyryl cyclic AMP, and cyclic AMP-dependent protein kinase.There was no Cl conductance response to a potassium gradient in vesicles buffered with imidazolium-acetate. Incorporation of ATP, AsO ₄ ^3– , and F^– into these nonconductive vesicles by homogenization, followed by addition of dibutyryl cAMP, produced substantial conductance activity. Maximal activation of Cl^– conductance was obtained with vesicles prepared in imidazolium-acetate buffering, using precautions to stabilize ATP and phosphoprotein prior to conductance measurements.     

Photosynthetic CO2 uptake byZea mays leaves as influenced by unilateral irradiation of adaxial and abaxial leaf surfaces

A study was made on the effect of increasing photon fluence rate (I) at a unilateral irradiation of adaxial (normal leaf position) and abaxial (inverse leaf position) blade surface of maize leaves of various insertion levels on net photosynthetic CO₂ uptake (P _n ) by the leaves, as well as the contribution of individual surfaces toP _n of the leaves, and the significance of, or relationship between the stomatal (g _s ) and intracellular (gm) conductances at the CO₂ transport.P _n of leaves of various age according to their insertion level was unaffected by the direction of incident irradiation. Upon irradiation of the leaves in normal and inverse position the contribution of the adaxial and abaxial surfaces toP _n ,g _s and g_m was different. On irradiating the leaves in normal position, the contribution of the irradiated adaxial surface to the characteristics mentioned made on the average 55% of total values, the contribution of the abaxial surface irradiated in inverse position made on the average 70% inP _n andg _m , and 80% ing _s . At lowerI’s g _m was higher thang _s both in irradiated and non-irradiated surfaces. The ratio ofg _s to g_m gradually got square with increasingI. In the irradiated adaxial surface the equilibrium (g _s /g _m = 1.0) took place at the highestI’s, in the irradiated abaxial surface between 500 to 1000 μmol m⁻² s⁻¹. The significance of the ratiog _m in the CO₂ transport through the individual surfaces is discussed.     

幼龄胡杨气孔行为对土壤质地和地下水埋深变化的响应

气孔调节是植物适应水分条件变化的关键途径,研究多变生境中植物气孔行为对认识植物的适应具有重要意义。洪水漫溢新形成的河漫滩是胡杨更新的自然生境,其土壤质地和地下水埋深具高度时空异质性。已有研究主要集中于胡杨对地下水埋深变化的生理生态响应,而对土壤质地与地下水变化交互作用影响植物水分关系的认识不足。通过设置土壤质地(砂土(S₁)、砂壤土(S₂)、黏壤土(S₃)与地下水埋深(W₁(30 cm)、W₂(60 cm)、W₃(90 cm))交互试验模拟幼龄胡杨自然生境,观测分析了不同条件下胡杨气孔导度(G_s)、气孔导度斜率(g₁)、光合的气孔限制(L_s)的变化。研究结果表明：(1)胡杨气孔行为对地下水变化的响应受土壤质地影响;(2)相同地下水埋深时不同土质间G_s具显著差异,W₁时S₂与S₃的G_s...     

Leaf responses to drought stress in Mediterranean accessions of Solanum lycopersicum: anatomical adaptations in relation to gas exchange parameters

In a previous study, important acclimation to water stress was observed in the Ramellet tomato cultivar (TR) from the Balearic Islands, related to an increase in the water‐use efficiency through modifications in both stomatal (g_s) and mesophyll conductances (g_m). In the present work, the comparison of physiological and morphological traits between TR accessions grown with and without water stress confirmed that variability in the photosynthetic capacity was mostly explained by differences in the diffusion of CO₂ through stomata and leaf mesophyll. Maximization of g_m under both treatments was mainly achieved through adjustments in the mesophyll thickness and porosity and the surface area of chloroplasts exposed to intercellular airspace (S_c). In addition, the lower g_m/S_c ratio for a given porosity in drought‐acclimated plants suggests that the decrease in g_m was due to an increased cell wall thickness. Stomatal conductance was also affected by drought‐associated changes in the morphological properties of stomata, in an accession and treatment‐dependent manner. The results confirm the presence of advantageous physiological traits in the response to drought stress in Mediterranean accessions of tomato, and relate them to particular changes in the leaf anatomical properties, suggesting specific adaptive processes operating at the leaf anatomical level.