黄龙山林区不同演替时期典型树种光诱导的气孔动力学研究

光诱导的气孔动力学响应快慢是影响植物叶水分利用效率的重要因素,为探索黄土高原不同演替阶段树种水分利用效率差异的生理机制,该研究以黄龙山林区典型树种(演替早期种山杨和白桦、演替后期种辽东栎)的幼龄实生苗为材料,采用盆栽试验,研究了叶片光诱导的气孔导度动力学参数差异及其与气孔特征、叶长期水分利用效率的关系。结果表明：(1)山杨和白桦气孔开放过程中气孔导度(g_s)增加的时间常数(K_i)小于辽东栎,但气孔关闭过程中气孔导度降低的时间常数(K_d)则大于辽东栎,表明山杨和白桦气孔开放更快,而辽东栎的气孔关闭更快。同时,气孔开放过程中山杨和白桦的g_s响应幅度均大于辽东栎,气孔关闭过程中山杨的g_s响应幅度亦大于辽东栎。(2)3种树种中,辽东栎的气孔密度最大,气孔最小,气孔指数最大,辽东栎气孔特征无法解释其慢速的气孔开放过程。 (3)山杨和白桦具有高的光合速率、最大羧化效率和最大电子传递速率,3种树种碳同位素比率(δ¹³C)表征的长期水分利用效率表现为山杨>白桦>辽东栎。研究认为,演替早期种山杨和白桦的高水分利用效率与其快速的气孔开放有关,而演替后期种辽东栎快速的气孔关闭并未增加其水分利用效率,且长期水分利用效率低于山杨和白桦,可能与辽东栎慢速的气孔开放限制了其光合速率有关。     

光照和水分对四季米仔兰幼苗生长的影响

四季米仔兰栽培历史悠久,是重要的造景树种。以1年生四季米仔兰幼苗为研究对象,设置3个光照处理(透光度为70%、50%、30%)和3个水分处理(田间持水量为70%、50%、30%),以透光度90%、田间持水量90%为对照,分析不同环境条件下四季米仔兰幼苗的生长状况和光合生理指标。结果表明：干旱胁迫和遮光抑制四季米仔兰幼苗的生长,且干旱胁迫的影响大于遮光。随着土壤水分的减少,株高增量、地径增量、净光合速率、蒸腾速率、气孔导度和叶绿素含量均显著降低,最大降幅分别为71.4%、81.2%、93.2%、71.5%、70.6%、30.4%;适当遮光(透光度50%)可缓解严重水分亏缺(田间持水量30%)对四季米仔兰幼苗生长的不利影响。透光度70%和田间持水量70%条件下株高增量、叶面积、净光合速率、蒸腾速率和气孔导度最大。最大荧光、可变荧光、PSⅡ潜在活性、PSⅡ最大光能转化效率随着水分减少呈先上升后下降趋势。四季米仔兰幼苗能够通过调整生长、提高叶绿素含量和调节光合系统来维持光合作用以适应胁迫环境。透光度70%和田间持水量70%有利于四季米仔兰幼苗光合作用的发挥,对其生长有积极影响。     

亚低温与干旱胁迫对番茄植株水分传输和形态解剖结构的影响

为探讨亚低温和干旱对植株水分传输的影响机制,以番茄幼苗为试材,利用人工气候室设置常温(昼25 ℃/夜18 ℃)和亚低温(昼15 ℃/夜8 ℃)环境,采用盆栽进行正常灌水(75%～85%田间持水量)和干旱处理(55%～65%田间持水量),分析了温度和土壤水分对番茄植株水分传输、气孔和木质部导管形态解剖结构的影响。结果表明: 与常温正常灌水处理相比,干旱处理使番茄叶水势、蒸腾速率、气孔导度、水力导度、茎流速率、气孔长度和叶、茎、根导管直径显著减小,而使叶、茎、根导管细胞壁厚度和抗栓塞能力增强;亚低温处理下番茄叶水势、蒸腾速率、气孔导度、水力导度和叶、茎、根导管直径显著降低,但气孔变大,叶、根导管细胞壁厚度和叶、茎、根抗栓塞能力显著升高。亚低温条件下土壤水分状况对番茄叶水势、蒸腾速率、气孔导度、水力导度、气孔形态、叶、根导管结构均无显著影响。总之,干旱处理下番茄通过协同调控叶、茎、根结构使植株水分关系重新达到稳态;亚低温处理下番茄植株水分关系的调控主要通过改变叶和根导管结构实现,且受土壤水分状况的影响较小。     

高温干旱复合胁迫及复水对刺槐幼苗水分运输的影响

近年来, 随着全球变暖, 部分地区干旱情况加重, 且高温干旱同时发生的概率增加, 对植物的生长与分布产生重要影响。采用室内模拟方法, 研究高温干旱复合胁迫对刺槐幼苗水分运输的影响。主要结果表明: 随胁迫程度增加, 比导率(K_s)、导水率(K_h)下降, 刺槐幼苗水分运输受阻, 40 ℃下田间持水量40%时 K_h、K_s 仅为对照的3.6%和5.3%; 气孔导度、蒸腾速率则在33 ℃下田间持水量70%时达到最大, 40 ℃下田间持水量40%时有所下降但仍高于对照; 复水后的补偿效应随胁迫的增加而降低, 轻度单一胁迫下各项指标在复水后均有所恢复, 但胁迫程度过大以及复合胁迫下补偿效应不明显。单一胁迫与复合胁迫之间存在差异, 高温干旱复合胁迫对刺槐幼苗水分运输影响较大, 且复水之后补偿效应不明显。     

耐冬山茶对不同光照和水分的生理生态学响应

耐冬山茶作为第三纪孑遗植物,是山茶自然分布最北缘的种群,具有丰富的形态特征与独特的遗传特性.以野生耐冬山茶幼苗为对象,设置2个光照梯度(全光照的65%、15%)、3个干旱梯度(田间持水量的75%、50%、25%),研究耐冬山茶在不同光照、水分条件下生理生态学响应机制,验证现存的4个理论假设是否能够解释耐冬山茶幼苗对遮荫与干旱的响应.结果表明:15%全光照限制了耐冬山茶幼苗的生长.与65%全光照相比,15%全光照使叶片的净光合速率、蒸腾速率和叶绿素含量下降,最大降幅分别为63.3%、82.9%和17.5%,显著提高了叶片的比叶面积、叶片含水量和PSⅡ最大光化学效率,最大分别提高了60.3%、8.3%和6.4%.干旱抑制耐冬山茶的生长,使株高、基径下降.随着干旱胁迫的加重,植株叶片的净光合速率、蒸腾速率和气孔导度显著降低,最小值分别为0.83μmol·m^-2·s^-1、0.30μmol·m^-2·s^-1和11.56 mmol·m-2·s-1.随干旱胁迫的加重,过氧化物酶和过氧化氢酶含量总体呈下降趋势,而丙二醛和脯氨酸含量显著上升.15%全光照缓解了干旱对耐冬山茶幼苗的消极影响,遮荫与干旱对耐冬山茶幼苗的交互作用符合"促进理论".耐冬山茶幼苗能够通过多种调节机制适应环境变化,且能适应较大的光照和水分范围.此外,通过改善耐冬山茶生长的光照和水分条件,为其提供理想的生长环境,可以扩大其园林应用.     

不同光环境下胡桃楸幼苗的形态可塑性及其响应研究

为了探求不同光环境对胡桃楸幼苗生长的影响,对全光照（100%光照）、中光照（60%光照）、低光照（30%光照）3种光环境下胡桃楸幼苗的生长、形态特征、生物量分配和水分特征开展研究。结果表明：胡桃楸幼苗的形态在不同光环境下存在明显的可塑性变化,生物量分配和水分特征均表现出不同程度的差异。低光照条件下,胡桃楸幼苗生长快,株高、地径分别为全光照的1.14、1.18倍;冠幅大,是全光照的1.40倍;叶片宽大,叶长和叶宽分别是全光照的1.25和1.36倍;分枝数明显少于全光照。3种光环境下胡桃楸幼苗地上部分生物量存在显著差异,地下部分差异不显著。叶片相对含水量随着光照的降低呈现逐渐增加的趋势;全光照条件下叶片饱和持水量与叶片干鲜比明显大于遮阴条件;3种光照条件下叶绿素含量差异显著。胡桃楸幼苗为适应不同光环境,在形态和生理方面都做出适应性调整,适当的遮阴处理有利于胡桃楸幼苗生长。     

外源脱落酸对干旱胁迫下滇润楠幼苗生长及生理特性的影响

以滇润楠一年生实生苗为试验材料,研究在良好水分条件(土壤含水量为70%～75%田间持水量)、轻度干旱胁迫及重度干旱胁迫处理下(50%～55%和30%～35%田间持水量)进行外源脱落酸(ABA)喷施对其生长及生理特性的影响。结果表明: 干旱胁迫使得滇润楠幼苗叶片的相对含水量、株高和生物量显著下降,净光合速率及叶绿素荧光参数(PSⅡ最大光化学效率,F_v/F_m)有不同程度的下降,而根冠比、膜脂过氧化产物丙二醛(MDA)含量显著增加。外源ABA的喷施可提高干旱胁迫下滇润楠幼苗的适应性,尤其是重度干旱下,外源ABA显著提高了叶片相对含水量21.0%,同时增加了植株株高和生物量的累积,提高了根冠比,为良好水分条件的2.1倍;减少了干旱下膜脂过氧化产物MDA的累积,提高了抗氧化酶过氧化氢酶、超氧化物岐化酶的活性,显著增加了脯氨酸的含量,为良好水分条件的7.7倍。外源ABA的喷施显著缓解了干旱胁迫对植株光合器官的不利影响,减少干旱引起的叶片净光合速率及气孔导度的下降,并且减轻了PSⅡ受到干旱的伤害程度,重度干旱下喷施ABA的植株的F_v/F_m显著高于未喷施ABA的植株。外源ABA的喷施可以减轻干旱对滇润楠植株的伤害,提高其抗旱性。     

异质性光对野牛草叶片解剖结构的影响

自然界中植物生长所需资源通常呈异质性分布, 具有发达匍匐茎的野牛草(Buchloe dactyloides)在蔓延过程中相连克隆分株常生活在异质性的光环境中。有研究证明, 在异质性光条件下, 植株幼叶的叶片解剖结构受成熟叶所处光照条件的影响, 而异质性光条件下克隆分株的叶片形态解剖结构是否也受相连分株所处光照条件的影响则未见报道。通过设置高光(全光照)和低光(遮阴)两个水平, 对由匍匐茎相连的野牛草克隆分株施以同质和异质性光处理, 研究了异质性光对野牛草叶片解剖结构的影响。结果发现: 在异质性光环境中, 遮阴的野牛草克隆分株的主脉直径、维管束鞘细胞个数、叶片厚度以及近轴侧和远轴侧叶肉细胞的厚度均显著降低; 同质性的低光处理对这些指标则没有显著影响。在异质性光处理下, 未遮阴姊株近轴侧和远轴侧叶肉细胞的厚度以及远轴侧的气孔大小显著增加, 而未遮阴的妹株近轴侧和远轴侧叶肉细胞的厚度、气孔密度和气孔大小、叶片厚度和维管束鞘细胞个数则会降低。同质高光处理下克隆分株近轴侧和远轴侧的气孔密度和气孔大小显著高于同质低光。野牛草克隆分株近轴侧和远轴侧叶肉细胞的厚度、气孔密度和气孔大小受相连分株所处光照条件的显著影响。该研究结果表明: 未遮阴的姊株因为与遮阴的妹株相连而显著受益, 而未遮阴的妹株则因为与遮阴的姊株相连而损耗严重; 在异质性光处理下, 遮阴分株叶片形态上缩减的可塑性生长是为减少维持其存活的消耗, 提高遮阴分株存活率的一种适应性表现。     

土壤水分胁迫对设施番茄叶片气孔特性的影响

为了研究土壤水分胁迫对设施番茄叶片气孔特性的影响,本研究以"金粉2号"为试材,于2013年5—8月设计4个土壤水分梯度试验[正常灌溉(田间持水量的70%~80%)、轻度胁迫(田间持水量的60%~70%)、中度胁迫(田间持水量的50%~60%)和重度胁迫(田间持水量的30%~40%)],利用数码显微成像系统和数码测距软件测定了叶片气孔参数。结果表明:番茄叶片气孔长度、宽度、气孔开张度和开张比均随水分胁迫程度的增加而减小,且随着胁迫时间的延长,其减小幅度不断增大;番茄气孔长宽的减小具有同步性,但气孔长度下降更为显著;随着水分胁迫程度的增加,气孔逐渐由长卵形转变为近圆形;随着土壤水分胁迫强度的增加,气孔上表皮气孔密度逐渐增大,而气孔下表皮密度呈先减小后增大的趋势。该研究揭示了土壤水分胁迫对设施番茄叶片气孔发展的影响规律,可为设施番茄水分管理提供科学依据。     

气温升高与干旱胁迫对宁夏枸杞光合作用的影响

以宁夏枸杞1年生苗木为材料,采用开顶式生长室模拟增温环境,设置两个温度水平(正常环境温度,增温=正常环境温度+2.5—3.7℃)和3个土壤水分水平(正常水分条件(田间最大持水量的70%—75%)、中度干旱处理(田间最大持水量的50%—55%)和重度干旱处理(田间最大持水量的35%—40%)),研究气温升高和干旱胁迫对宁夏枸杞光合作用的影响。结果表明:(1)在增温条件下,中度和重度干旱处理下的净光合速率比对照(正常供水)分别下降17.5%、48.9%,气孔导度平均下降了3.9%,水分利用效率仅为正常环境温度下的57.8%。(2)在气温升高和干旱胁迫交互作用下,枸杞叶片的净光合速率、气孔导度、胞间CO2浓度显著下降的同时,增温处理又加剧了枸杞植株的蒸腾耗水,从而导致枸杞叶片水分的利用效率和CO2同化能力降低。(3)气温升高和干旱胁迫交互作用降低了枸杞的PSⅡ活性中心的光能转换效率、使光合机构和PSⅡ反应中心受到损伤,从而导致枸杞光合作用效率下降。(4)气温升高加剧了干旱胁迫对宁夏枸杞叶片净光合速率和水分利用效率的减小作用,即气温升高加剧了干旱胁迫对宁夏枸杞光合作用的抑制作用。     

Dominant negative guard cell K+ channel mutants reduce inward-rectifying K+ currents and light-induced stomatal opening in arabidopsis

Inward-rectifying potassium (K+(in)) channels in guard cells have been suggested to provide a pathway for K+ uptake into guard cells during stomatal opening. To test the proposed role of guard cell K+(in) channels in light-induced stomatal opening, transgenic Arabidopsis plants were generated that expressed dominant negative point mutations in the K+(in) channel subunit KAT1. Patch-clamp analyses with transgenic guard cells from independent lines showed that K+(in) current magnitudes were reduced by approximately 75% compared with vector-transformed controls at -180 mV, which resulted in reduction in light-induced stomatal opening by 38% to 45% compared with vector-transformed controls. Analyses of intracellular K+ content using both sodium hexanitrocobaltate (III) and elemental x-ray microanalyses showed that light-induced K+ uptake was also significantly reduced in guard cells of K+(in) channel depressor lines. These findings support the model that K+(in) channels contribute to K+ uptake during light-induced stomatal opening. Furthermore, transpirational water loss from leaves was reduced in the K+(in) channel depressor lines. Comparisons of guard cell K+(in) current magnitudes among four different transgenic lines with different K+(in) current magnitudes show the range of activities of K+(in) channels required for guard cell K+ uptake during light-induced stomatal opening.     

赤皮青冈幼苗叶片解剖结构对干旱胁迫的响应

以浙江庆元、湖南洞口和湖南靖州3个种源的赤皮青冈1年生幼苗为材料,采用盆栽称量法控制土壤水分含量,设置土壤相对含水量分别为75%～80%(对照)、55%～60%(轻度干旱胁迫)、45%～50%(中度干旱胁迫)和30%～35%(重度干旱胁迫),研究不同程度干旱胁迫对赤皮青冈幼苗叶片解剖结构和蒸腾作用的影响.结果表明: 干旱胁迫下,3个种源赤皮青冈幼苗叶片的总厚度、上下表皮厚度和栅栏组织厚度均显著降低.栅栏组织厚度与海绵组织厚度比(栅海比)、气孔长度和宽度随干旱程度的增强而显著减小,而气孔密度随干旱胁迫程度的增强而显著增加.干旱处理对叶片主脉厚度无显著影响,木质部厚度的变化因种源而异.叶片结构的变化引起生理功能改变,随着胁迫程度的加强,赤皮青冈幼苗的蒸腾速率显著降低.对照和各干旱处理湖南洞口种源幼苗叶片的下表皮厚度、栅海比、气孔密度显著大于其他2个种源,蒸腾速率显著小于其他2个种源,表明湖南洞口赤皮青冈对干旱胁迫的适应性较强.     

丛枝菌根真菌对杨树生长、气孔和木质部微观结构的影响

植物气孔与木质部导管及纤维的功能直接关系着植物的水分利用, 进而影响植物的生长。为研究丛枝菌根真菌(AMF)对杨树抗旱性的影响, 采用温室盆栽的方法, 研究两种水分条件下, 接种根内球囊霉(Rhizophagus irregularis)对速生杨107 Populus × canadensis (P. nigra × P. deltoides) ‘Neva’气孔及木质部微观结构的影响。结果表明: AMF的侵染显著提高了杨树幼苗地上和地下部分生物量, 对叶片气孔长度、茎部导管细胞直径和纤维细胞长度也有促进作用。AMF对生物量和导管细胞直径的增加幅度表现出干旱条件下>正常水分条件下, 而对气孔长度的提高幅度表现出干旱条件下<正常水分条件下。正常水分条件下, AMF增加了杨树叶片的气孔密度, 减小了纤维细胞直径, 对相对水分饱和亏缺无影响; 干旱条件下, AMF增加了纤维细胞直径, 降低了相对水分饱和亏缺, 对气孔密度无影响。综上所述, 干旱条件下, AMF对导管水分传输能力的促进作用明显增加, 而对气孔蒸腾能力的促进作用有所减少, 从而更利于杨树在遭遇干旱时保持水分, 减少干旱对菌根杨树造成的水分亏缺, 提高菌根杨树对干旱的耐受性。     

拟南芥微丝加帽蛋白β亚基参与壳梭孢素诱导的气孔开放过程

气孔是植物响应外源信号,与环境进行水分和气体交换的门户。由外源信号引起的保卫细胞微丝骨架动态变化在气孔运动中发挥重要作用,但是具体的精确调节机制仍不清楚。微丝结合蛋白家族(ABPs) 是微丝动态组装最直接的调控者,它们的作用不容忽视。本文运用反向遗传学,以微丝结合蛋白—加帽蛋白 (CP) β-亚基 (CPB) 突变体cpb-3为实验材料,探究其在壳梭孢素 (FC)诱导气孔开放中的作用。结果发现:离体叶片干燥3 h,cpb-3突变体的叶片失水率为63.45%,明显高于野生型的48.99%。气孔开度测量及激光共聚焦显微镜观察发现,cpb-3突变体的气孔开放程度以及微丝动态重排对FC分子更敏感。气孔开度相比野生型增大了20% (P<0.05),含辐射状微丝排布的保卫细胞数量比例增幅达到58.3%,比对照组高出18.5%。此外,非损伤微测技术记录保卫细胞Ca²⁺、K⁺等跨膜运输动态,FC处理下,cpb-3突变体保卫细胞中Ca²⁺外流速度升至212.86 pmol cm^-2s^-1,野生型仅为68.76 pmol cm^-2s^-1,明显快于野生型。且K⁺内流也有相同表现。综上表明,微丝加帽蛋白CP的β亚基CPB可能通过调节保卫细胞微丝骨架动态重排以及离子流动,在FC诱导的气孔运动中发挥重要的作用。     

Comparison of the physiological responses of Phaseolus vulgaris and Vigna unguiculata cultivars when submitted to drought conditions

Three cultivars differing in their susceptibility to water stress were compared—Phaseolus vulgaris cv. Carioca (susceptible), Vigna unguiculata cv. IT83D (intermediately tolerant) and V. unguiculata cv. EPACE-1 (tolerant)—during an imposed water stress treatment. Variation in leaf gas exchange (i.e. assimilation and stomatal conductance) and leaf relative water content in response to progressive substrate water depletion were investigated. To verify the extent of the injury caused by the drought treatment, leaf gas exchange was measured after rehydration. In the three cultivars, stomatal conductance declined before leaf relative water content was affected. P. vulgaris showed the largest decrease in the rate of stomatal conductance with decreasing substrate water content compared to both V. unguiculata cultivars. Photosynthetic assimilation rates were largely dependent on stomatal aperture, but there was evidence of the participation of non-stomatal factors in the reduction of CO₂ fixation. The response of leaf gas exchange parameters to severe water stress conditions differed significantly between P. vulgaris and V. unguiculata cultivars. After rehydration, cultivars can be characterised according to the degree of injury induced by the drought treatment: V. unguiculata cv. EPACE-1 as the least affected, V. unguiculata cv. IT83D slightly affected and P. vulgaris cv. Carioca strongly affected. Similar ranking was obtained with experiments previously performed at a cellular and subcellular level. Our results confirm the utility of physiological parameters as early screening tools for drought resistance in bean cultivars.     

Oligogalacturonic Acid and Chitosan Reduce Stomatal Aperture by Inducing the Evolution of Reactive Oxygen Species from Guard Cells of Tomato and Commelina communis

Stomatal opening provides access to inner leaf tissues for many plant pathogens, so narrowing stomatal apertures may be advantageous for plant defense. We investigated how guard cells respond to elicitors that can be generated from cell walls of plants or pathogens during pathogen infection. The effect of oligogalacturonic acid (OGA), a degradation product of the plant cell wall, and chitosan (beta-1,4-linked glucosamine), a component of the fungal cell wall, on stomatal movements were examined in leaf epidermis of tomato (Lycopersicon esculentum L.) and Commelina communis L. These elicitors reduced the size of the stomatal aperture. OGA not only inhibited light-induced stomatal opening, but also accelerated stomatal closing in both species; chitosan inhibited light-induced stomatal opening in tomato epidermis. The effects of OGA and chitosan were suppressed when EGTA, catalase, or ascorbic acid was present in the medium, suggesting that Ca(2+) and H(2)O(2) mediate the elicitor-induced decrease of stomatal apertures. We show that the H(2)O(2) that is involved in this process is produced by guard cells in response to elicitors. Our results suggest that guard cells infected by pathogens may close their stomata via a pathway involving H(2)O(2) production, thus interfering with the continuous invasion of pathogens through the stomatal pores.     

Reductions in mesophyll and guard cell photosynthesis impact on the control of stomatal responses to light and CO2

Transgenic antisense tobacco plants with a range of reductions in sedoheptulose-1,7-bisphosphatase (SBPase) activity were used to investigate the role of photosynthesis in stomatal opening responses. High resolution chlorophyll a fluorescence imaging showed that the quantum efficiency of photosystem II electron transport (F(q)(')/F(m)(')) was decreased similarly in both guard and mesophyll cells of the SBPase antisense plants compared to the wild-type plants. This demonstrated for the first time that photosynthetic operating efficiency in the guard cells responds to changes in the regeneration capacity of the Calvin cycle. The rate of stomatal opening in response to a 30 min, 10-fold step increase in red photon flux density in the leaves from the SBPase antisense plants was significantly greater than wild-type plants. Final stomatal conductance under red and mixed blue/red irradiance was greater in the antisense plants than in the wild-type control plants despite lower CO(2) assimilation rates and higher internal CO(2) concentrations. Increasing CO(2) concentration resulted in a similar stomatal closing response in wild-type and antisense plants when measured in red light. However, in the antisense plants with small reductions in SBPase activity greater stomatal conductances were observed at all C(i) levels. Together, these data suggest that the primary light-induced opening or CO(2)-dependent closing response of stomata is not dependent upon guard or mesophyll cell photosynthetic capacity, but that photosynthetic electron transport, or its end-products, regulate the control of stomatal responses to light and CO(2).     

遮荫对黑茶藨子叶片形态结构和光合特性的影响

以黑茶藨子为试验材料,通过人工遮荫的方式,研究了不同遮荫强度（全光照、20%和60%遮荫）和遮荫时间（初期、中期和后期）对黑茶藨子叶片形态解剖结构和光合特性的影响。结果表明：（1）20%、60%遮荫处理的叶片厚度均显著低于全光照处理,上下表皮厚度则高于全光照处理;随着遮荫强度的加大,栅栏组织与海绵组织厚度比值大小均呈减少趋势,随着遮荫时间的延长,呈增加趋势。（2）遮荫初期和中期,20%遮荫处理的叶片净光合速率（P_n）比全光照和60%遮荫处理的值略高,但差异并不显著（P>0.05）,其蒸腾速率（T_r）、水分利用效率（WUE）也略有增加;但是,60%遮荫处理的叶片净光合速率（P_n）显著低于全光照处理（P<0.05）。遮荫后期,60%遮荫处理的叶片净光合速率（P_n）显著高于全光照处理,且水分利用效率（WUE）、气孔导度（G_s）、蒸腾速率（T_r）均显著高于全光照和20%遮荫处理。综上所述,遮荫处理导致叶片厚度减少,海绵组织比例增加,有利于减少透射光中的光量子丧失,提高光能利用效率;生长早期和中期作20%轻度遮荫处理,后期作60%中度遮荫处理能提高植株对光和水分的利用效率、维持较高的光合速率、延缓衰老。