不同植物叶片水分利用效率对光和CO2的响应与模拟

植物叶片水分利用效率的高低取决于气孔控制的光合作用和蒸腾作用两个相互耦合的过程,模拟水分利用效率对环境变化的响应特征和机制是理解生态系统碳循环和水循环及其耦合关系的基础。研究通过人工控制光强和CO₂浓度,对叶片水分利用效率进行了研究。提出了植物水分利用效率在光强和CO₂浓度共同作用下的估算模型。数据分析表明,该模型在包括C3和C4植物、草本和木本植物在内的9种植物上能很好地模拟水分利用效率对光强和CO₂浓度共同作用的响应。该模型可以用于估算CO₂浓度升高条件下光合速率的提高和蒸腾速率的降低对水分利用效率提高的贡献量。CO₂浓度变化条件下,水分利用效率在不同植物之间有巨大差异,研究区域尺度植物的水分利用效率时至少需要将植物区分为C4植物和C3植物,其中C3植物区分为草本和木本植物3种生态功能型才能较为准确地估算植物的整体水分利用效率。应用本研究提出的水分利用效率估算模型和植物水分利用效率生态功能型分类标准,可以为建立以植物的水分利用效率为基本参数的陆地生态系统水循环模型和陆地生态系统生产力模型提供重要依据。     

陆地生态系统水分利用效率对气候变化的响应研究进展

气候变化显著影响陆地生态系统生产力以及水分利用格局,而水分利用效率(Water Use Efficiency,WUE)是衡量生态系统碳水耦合关系的重要指标之一。研究陆地生态系统水分利用效率对气候变化的响应,有助于深入理解生态系统的变化规律,模拟和预测生态系统碳水过程的发展状况,从而为应对全球气候变化提供新的依据。为了更好地掌握生态系统水分利用效率研究现状以及其对温度、CO2等关键气候因子的响应情况,本文总结了陆地生态系统水分利用效率对气候变化响应的最新研究进展。首先介绍了相关的定义并归纳了两种不同计算方式的差异和特点;接着重点总结了陆地生态系统水分利用效率对大气温度、CO2、水分、干旱以及太阳辐射等影响因素的响应;最后文章总结了目前3个相关的研究态势,主要包括:(1)长时间序列水分利用效率与气候要素的关系研究;(2)土地利用/覆被变化对水分利用效率的影响及其对气候的反馈研究;(3)多尺度水分利用效率综合研究。本研究可为深入研究生态系统过程对气候变化的响应提供参考。     

28种园林植物对大气CO2浓度增加的生理生态反应

通过对28种园林植物在不同CO2浓度水平下的气体交换参数的观测,分析了净光合速率、气孔导度、蒸腾速率和水分利用效率等生理生态指标的变化趋势与规律.结果表明,所测植物净光合速率和水分利用效率随CO2浓度升高而线性增加,但不同植物种类对高CO2浓度的反应存在较大差异.气孔导度和蒸腾速率与CO2浓度呈线性负相关关系.当CO2浓度倍增(350～700 μmol·mol-1)时,28种园林植物净光合速率平均提高31.2%,气孔导度降低16.5%,蒸腾速率下降11.7%,而水分利用效率则提高了49.2%.不同光合途径的植物净光合速率和水分利用效率受CO2浓度增加的影响程度为C3植物较大,C4植物较小, CAM植物介于两者之间.对不同生活型植物而言,影响程度则为草本C3植物较大,乔木C3植物较小,灌木C3植物居于两者之间.     

陆生植物水分利用效率

植物水分利用效率（water use efficiency,WUE）作为叶片光合与水分生理过程的耦合因子,不仅是联系植被生态系统碳循环与水循环的重要变量,同时亦已成为揭示陆地植被生态系统对全球变化响应和适应对策的重要手段。稳定同位素技术和涡度相关技术的发展和应用,使植物WUE的概念和测定方法不断得到扩展,研究内容、尺度也不断拓宽。深入认识植物WUE的变化特征及其调控机制,一方面有助于揭示不同植物对生境的生理生态适应机理,另一方面能够促进对陆地生态系统碳-水平衡关系的理解。目前生态系统水平WUE的研究尚处初始阶段。如何建立不同尺度水平WUE间的联系机制,将成为今后该研究领域的关注点。本文在阐述植物WUE概念和测定方法的基础上,综述了植物叶片水平WUE的影响因子、种间差异与水分利用策略,以及WUE与其他叶性状的关系,介绍了当前生态系统水平WUE的研究状况,提出未来的研究趋势。     

武夷山不同海拔植物水分利用效率的变化及其与养分变化的关系

以武夷山不同海拔(600、900、1300、1500、1800、2000和2100 m)的乔木、灌木和草本3种生活型植物为研究对象,观测其水分利用效率和叶片氮、磷养分浓度随海拔的变化趋势,旨在探索海拔梯度间水分、养分变化与植物水分利用效率变化的关系.结果表明: 植物水分利用效率随海拔的增加呈显著上升趋势,乔木叶片δ¹⁸O随海拔变化不显著.总体上看,叶片氮浓度未观测到规律性的变化,高海拔地区的叶片磷浓度显著高于低海拔地区.水分利用效率与叶片磷浓度呈显著正相关,而与叶片氮浓度相关性不显著.不同海拔植物水分利用效率变化主要由光合速率的变化引起,水分状况对植物水分利用效率的影响不显著.海拔梯度间植物叶片磷浓度的差异对光合速率影响显著,进而影响水分利用效率.     

浑善达克沙地不同植物功能型光合作用和水分利用特征的比较

为了比较不同植物功能型在沙地生境下光合作用和水分利用效率的差异,测定了浑善达克沙地3种功能型的代表种的气体交换特征来比较它们的光合碳固定能力和水分利用状况。3个代表种的气体交换日变化结果表明乔木的光合速率和水分利用效率比草本和灌木的低,而蒸腾速率和气孔导度较高,经过中午的光合午休后,乔木的光合速率在下午没有恢复,而草本和灌木都有不同程度的恢复。在所测定的所有代表物种中,研究地全部的乔木(3种)和灌木(6种)以及典型的草本(2 5种) ,气孔导度与光合速率和蒸腾速率都成显著的正相关关系;另外,在同样的叶片水势情况下,乔木植物的气孔导度最低,在同样的蒸腾速率情况下,乔木植物的光合速率最低。这些结果表明乔木在CO2 同化和H2 O蒸腾平衡上具有低的水分利用效率。从这个角度考虑,我们认为在对沙地进行恢复时,一些草本和灌木种比乔木更合适     

不同CO2浓度下番茄幼苗叶片的光能利用效率

光能利用效率(LUE)是评价植物叶片光能利用能力的重要参数,更是影响生态系统生产力大小和质量的主要因素.本文基于植物光合作用对光响应的机理模型推导出植物叶片的光能利用效率模型以及叶片的最大光能利用效率(LUE_max)和对应的饱和光强(I_L-sat)的数学表达式,并用光能利用效率模型研究了番茄幼苗叶片在CO₂浓度分别为350、450、550和650 μmol·mol^-1下的光能利用效率.拟合结果表明: 所推导的叶片光能利用效率模型可以很好地描述4种CO₂浓度条件下番茄幼苗叶片的光能利用效率;在这4种CO₂浓度条件下,番茄的LUE_max在光合有效辐射(I)为70～90 μmol·m^-2·s^-1时就可以达到;番茄在CO₂浓度为550和650 μmol·mol^-1时叶片的LUE_max和I_L-sat没有差异.产生这种现象的原因可能是由于番茄幼苗长时间处于较低光强下,番茄幼苗叶片的光合功能已经适应了低光强环境,以致于高CO₂浓度难以改变它的捕光色素分子的内秉特性,如有效光能吸收截面以及处于激发态和基态色素的比例等.     

森林生态系统碳水关系及其影响因子研究进展

森林生态系统的碳水关系是陆地生态系统碳循环和水循环相互耦合的作用过程,对研究森林碳汇、森林生态水文过程和全球变化响应有重要意义.在全球变化背景下,森林生态系统碳水关系已成为生态水文学领域中的一个热点科学问题.本文在总结国际上森林碳汇研究的基础上,概述了森林碳水关系的过程机制,包括森林水分利用效率、不同尺度上的碳水关系、尺度推绎和碳水关系的模拟研究方面的进展;总结了影响森林碳水关系的因子和研究进展,包括水分条件、CO₂浓度升高、增温、氮沉降、臭氧浓度变化、辐射因子和海拔梯度因子对森林碳水关系的影响;最后对已有研究存在的问题进行了初步分析,并对未来研究内容和方向进行了展望.     

北京西山侧柏林冠层不同高度处叶片水分利用效率

以北京西山广泛分布的侧柏林为研究对象,综合考虑冠层不同高度处气象因子、大气CO₂浓度以及大气CO₂中碳同位素组成的差异,对其冠层不同高度处叶片的瞬时水分利用效率和短期水分利用效率分别进行了测定,以期为区域森林生态系统固碳与耗水研究提供理论依据,为区域森林生态系统经营与维护提供技术支撑.结果表明: 侧柏林冠层不同高度处叶片的瞬时水分利用效率随冠层高度的变化规律表现为上层>中层>下层,多种气象因子协同影响气孔运动,使瞬时水分利用效率受气孔限制;侧柏林冠层不同高度处的环境因子、大气CO₂浓度以及大气CO₂的δ13C均存在一定差异,导致了林冠各层叶片的短期水分利用效率的变化.林冠上层叶片通过提高水分利用效率适应环境.     

全球气候变化下植物水分利用效率研究进展

气候变化是20世纪80年代以来全球最为关注的环境问题之一,显著影响着植物的生产力以及水分运移和利用格局,改变植物个体、群落及生态系统的水分利用效率（WUE）,最终影响植被分布格局和群落结构.开展植物WUE的研究有助于理解和预测陆地植被对全球变化的响应和适应对策,从而为应对全球变化提供新的依据.本文从叶片、个体、群体或生态系统等不同尺度简要介绍了植物水分利用效率的概念及测定方法,着重综述了气候变暖、CO₂浓度升高、降水变化和氮沉降等重要气候因子及其复合作用对植物WUE的影响研究进展,以及不同立地条件下植物WUE变化特征及生存适应策略,指出当前研究中存在的问题,并对全球气候变化下植物WUE的研究进行展望.     

Responses of water use efficiency of 9 plant species to light and CO2 and their modeling

Photosynthesis coupled with transpiration determines water use efficiency (WUE) at leaf level, and the responses of WUE controlled by gas exchanges through stomata to environment are the basis of carbon and water cycles in the ecosystem. In this paper, by using Li-6400 Portable Photosynthesis System (LI-COR), WUE at leaf level was analyzed under controlled photosynthetic photons flux density (PPFD) and CO₂ concentration conditions across 9 plant species including maize (Zea mays), sorghum (Sorghum vulgare), millet (Setaria italica), soybean (Glycine max), peanut (Arachis phyogaea), sweet potato (Ipomoea batatas), rice (Oryza sativa), Masson pine (Pinus massoniana) and Schima superba. We had developed a new model to estimate the water use efficiency in response to the combined effects of light and CO₂ concentration. Our measured data validated that this model could simulate the changes of water use efficiency very well under combined effect of light and CO₂ concentration. It could be used to estimate contribution of photosynthesis increase and transpiration decline on water use efficiency with the rising of CO₂ concentration. Great differences in water use efficiency occurred in these different plant species under various CO₂ concentration levels. Based on water use efficiency at regional scale, we concluded that plants should be separated into C₃ plants and C₄ plants, and furthermore, C₃ plants should be separated into herbaceous plants and woody plants. Our separation criteria would do a great favor in modeling the evapotranspiration of terrestrial ecosystem with carbon and water balance.     

短期CO2加富对凤梨光合作用及生长发育的影响

 研究了CO₂加富对丹尼斯凤梨（Guzmania`Denise’）和吉利凤梨（Guzmania `Cherry’）叶片光合速率、植株生长、开花和光合相关酶活性的 影响。结果表明,处理30 d期间,处理(600±40)、(900±40) μmol CO₂&;#8226;mol^-1的净光合速率分别比同期对照增加了6.24%～31.91%和11.92%～ 41.48%;CO₂加富下促进了叶片中可溶性糖和淀粉的积累, 蒸腾速率和气孔导度下降,Rubisco活性增加,乙醇酸氧化酶活性则明显下降。(600 ±40)μmol CO₂&;#8226;mol^-1处理下的株高、叶面积分别比同期对照下增加了6.94%～14.63%和1.66%～7. 06%,而处理(900±40) μmol CO₂&;#8226;mol^-1下 分别增加了9.71%～20.85%和2.87%～11.62%;CO₂加富下促进了干重和鲜重的积累。此外,CO₂加富提前了吉利凤梨的花期。     

CO2浓度倍增对8种作物叶片光合作用、蒸腾作用和水分利用效率的影响

揭示作物光合作用、蒸腾作用和水分利用效率(WUE)对大气CO₂浓度变化的响应, 对预测未来大气CO₂浓度升高条件下作物生产力与需水规律的变化具有重要意义。在自然CO₂浓度、CO₂倍增和倍增后恢复到自然CO₂浓度3种情况下, 对大豆(Glycine max)、甘薯(Ipomoea batatas)、花生(Arachis hypogaea)、水稻(Oryza sativa)、棉花(Gossypium hirsutum)、玉米(Zea mays)、高粱(Sorghum vulgare)和谷子(Setaria italica) 8种作物的气体交换参数进行了研究。结果表明: CO₂浓度倍增可以提高光合速率, 降低蒸腾速率, 从而提高WUE, 其中光合速率提高的贡献更大; C₃比C₄作物的光合速率、WUE增幅大, C₃作物光合速率提高对WUE的贡献大于C₄作物; 通过对比倍增后恢复到自然CO₂浓度时气体交换参数随环境条件变化的响应确定了其内在调控机制; 倍增后恢复到自然CO₂浓度时作物光合速率低于自然CO₂浓度下的光合速率, 而蒸腾速率无明显差异。由此判断: CO₂浓度倍增下存在光合下调现象, 这可能是由于Rubisco酶蛋白含量、活化水平和比活性降低等“非气孔因素”造成的, 并非由气孔导度的降低引起的。     

The efficiency of water use in water stressed plants is increased due to ABA induced stomatal closure

Gas exchange and abscisic acid content of Digitalis lanata EHRH. have been examined at different levels of plant water stress. Net photosynthesis, transpiration and conductance of attached leaves declined rapidly at first, then more slowly following the withholding of irrigation. The intercellular partial pressure of CO₂ decreased slightly. The concentration of 2-cis(S)ABA increased about eight-fold in the leaves of non-irrigated plants as compared with well-watered controls. A close linear correlation was found between the ABA content of the leaves and their conductance on a leaf area basis. In contrast, the plot of net assimilation versus ABA concentration was curvilinear, leading to an increased efficiency of water use during stress. After rewatering, photosynthesis reached control values earlier than transpiration, leaf conductance and ABA content. From these data it is concluded that transpiration through the stomata is directly controlled by the ABA content, whereas net photosynthesis is influenced additionally by other factors.Possible reasons for the responses of photosynthesis and water use efficiency to different stress and ABA levels are discussed.Abbreviations A net CO₂ assimilation - ABA abscisic acid - C_i intercellular CO₂ concentration - g stomatal conductance - T transpiration - WUE water use efficiency     

Water‐use efficiency in response to climate change: from leaf to ecosystem in a temperate steppe

Water‐use efficiency (WUE) has been recognized as an important characteristic of ecosystem productivity, which links carbon (C) and water cycling. However, little is known about how WUE responds to climate change at different scales. Here, we investigated WUE at leaf, canopy, and ecosystem levels under increased precipitation and warming from 2005 to 2008 in a temperate steppe in Northern China. We measured gross ecosystem productivity (GEP), net ecosystem CO₂ exchange (NEE), evapotranspiration (ET), evaporation (E), canopy transpiration (T_c), as well as leaf photosynthesis (P_max) and transpiration (T_l) of a dominant species to calculate canopy WUE (WUE_c=GEP/T), ecosystem WUE (WUE_gep=GEP/ET or WUE_nee=NEE/ET) and leaf WUE (WUE_l=P_max/T_l). The results showed that increased precipitation stimulated WUE_c, WUE_gep and WUE_nee by 17.1%, 10.2% and 12.6%, respectively, but decreased WUE_l by 27.4%. Climate warming reduced canopy and ecosystem WUE over the 4 years but did not affect leaf level WUE. Across the 4 years and the measured plots, canopy and ecosystem WUE linearly increased, but leaf level WUE of the dominant species linearly decreased with increasing precipitation. The differential responses of canopy/ecosystem WUE and leaf WUE to climate change suggest that caution should be taken when upscaling WUE from leaf to larger scales. Our findings will also facilitate mechanistic understanding of the C–water relationships across different organism levels and in projecting the effects of climate warming and shifting precipitation regimes on productivity in arid and semiarid ecosystems.     

冬小麦光合特征及叶绿素含量对保水剂和氮肥的响应

以不施保水剂和氮（N）肥为对照,测定了保水剂（60 kg·hm^-2）与不同N肥水平（0、225、450 kg·hm^-2）及其配施条件下大田小麦的光合特征、叶绿素含量和水分利用效率等指标,研究了冬小麦拔节期和灌浆期光合生理特征、叶绿素含量及水分利用对保水剂和N肥的响应.结果表明：灌浆期各处理的光合速率、气孔导度、胞间CO₂浓度、叶片水分利用效率及叶绿素含量均大于拔节期.在拔节期,单施N肥条件下,随施N量的增加,单叶水分利用效率提高,光合速率、气孔导度、胞间CO₂浓度及蒸腾速率均先增后减;225 kg·hm^-2 N肥处理的叶绿素含量最高.施用保水剂后,随施N量的增加,胞间CO₂浓度降低,而光合速率等均提高;单施保水剂及其与N肥配施提高了叶绿素含量,而过多N肥效果不显著在灌浆期,单施N肥显著提高了小麦的光合速率及水分利用效率,降低了气孔导度、胞间CO₂浓度及蒸腾速率;叶绿素含量随N肥用量的增加而增加.施用保水剂后,随N肥用量的增加,光合速率和叶片水分利用效率均先增后减,而胞间CO₂浓度和蒸腾速率先减后增,但均低于对照,气孔导度随施N量的增加而提高.单施保水剂的叶绿素含量显著提高,但其与N肥配施叶绿素含量有所降低.保水剂与N肥配合施用显著提高了小麦的千粒重、产量及水分生产效率.其中,保水剂与225 kg·hm^-2N肥配施处理的产量及水分生产效率均最高.     

Observed and modelled historical trends in the water‐use efficiency of plants and ecosystems

Plant water‐use efficiency (WUE, the carbon gained through photosynthesis per unit of water lost through transpiration) is a tracer of the plant physiological controls on the exchange of water and carbon dioxide between terrestrial ecosystems and the atmosphere. At the leaf level, rising CO₂ concentrations tend to increase carbon uptake (in the absence of other limitations) and to reduce stomatal conductance, both effects leading to an increase in leaf WUE. At the ecosystem level, indirect effects (e.g. increased leaf area index, soil water savings) may amplify or dampen the direct effect of CO₂. Thus, the extent to which changes in leaf WUE translate to changes at the ecosystem scale remains unclear. The differences in the magnitude of increase in leaf versus ecosystem WUE as reported by several studies are much larger than would be expected with current understanding of tree physiology and scaling, indicating unresolved issues. Moreover, current vegetation models produce inconsistent and often unrealistic magnitudes and patterns of variability in leaf and ecosystem WUE, calling for a better assessment of the underlying approaches. Here, we review the causes of variations in observed and modelled historical trends in WUE over the continuum of scales from leaf to ecosystem, including methodological issues, with the aim of elucidating the reasons for discrepancies observed within and across spatial scales. We emphasize that even though physiological responses to changing environmental drivers should be interpreted differently depending on the observational scale, there are large uncertainties in each data set which are often underestimated. Assumptions made by the vegetation models about the main processes influencing WUE strongly impact the modelled historical trends. We provide recommendations for improving long‐term observation‐based estimates of WUE that will better inform the representation of WUE in vegetation models.     

Response of Photosynthesis, Stomatal Conductance and Water Use Efficiency to Elevated CO2 and Nutrient Supply in Acclimated Seedlings of Phaseolus vulgaris L.

Plants of Phaseolus vulgaris L were grown from seed in open-topgrowth chambers at present day (350 µmol mol^–1)and double the present day (700 µmol mol^–1) atmosphericCO₂ concentration with either low (L, without additional nutrientsolution) or relatively high (H, with additional nutrient solution)nutrient supply Measurements of assimilation rate, stomatalconductance and water use efficiency were started 17 d aftersowing on each fully expanded, primary leaf of three plantsper treatment Measurements were made in external CO₂ concentrations(C₂) of 200, 350, 450, 550 and 700 µmol mol^–1 andrelated to both C_a and to C₁, the mean intercellular space CO₂concentration Fully adjusted, steady state measurements weremade after approx 2 h equilibration at each CO₂ concentration The rate of CO₂ assimilation by leaves increased and stomatalconductance decreased similarly over the range of C_a or C₁ inall four CO₂ and nutrient supply treatments but both assimilationrate and stomatal conductance were higher in the high nutrientsupply treatment than in the low nutrient treatment The relationbetween assimilation rate or stomatal conductance and C₁ wasnot significantly different amongst plants grown in present-dayor elevated CO₂ concentration in either nutrient supply treatment,i e there was no evidence of down regulation of photosynthesisor stomatal response Increase in CO₂ concentration from 350to 700 µmol mol^–1 doubled water use efficiency ofindividual leaves in the high nutrient supply treatment andtripled water use efficiency in the low nutrient supply treatment The results support the hypothesis that acclimation phenomenaresult from unbalanced growth that occurs after the seed reservesare exhausted, when the supply of resources becomes growth limiting CO₂ enrichment, Phaseolus vulgaris L., net CO₂ assimilation rate, stomatal conductance, water use efficiency     

Gibberellic acid affects growth and flowering of Philodendron‘Black Cardinal’

Changes in net photosynthetic rate (P_N), stomatal conductance (g_s), intercellular CO₂ concentrations (C_i), transpiration rate (E) and water use efficiency (WUE) were measured in Plantago major L. plants grown under sufficient soil water supply or under soil water stress conditions. The plants had high P_N in a wide range of soil water potential and temperature regimes. Soil water had little effect on P_N under ambient CO₂ concentrations, which was explained by a high carboxylation rate, but increased the dark respiration rate. Carboxylation activity at low C_i depended on RuBP regeneration, whereas at high C_i it depended on the phosphate regeneration rate. The g_s and E values were low in plants under stress as compared to the controls that resulted in an increase of WUE. The results obtained show that Plantago major plants have different ways of adaptation to soil water deficit conditions.