植物气孔导度的机理模型

Ball-Berry气孔导度模型及其修正模型是评价植物叶片气孔调节的重要工具。该文从CO₂分子在叶片气孔中扩散这个最基本的物理过程出发, 应用物理学中的分子扩散和碰撞理论、流体力学与植物生理学等知识, 严格推导出叶片气孔导度的机理模型。利用美国Li-Cor公司生产的Li-6400光合作用测定仪控制CO₂浓度、湿度和温度, 测量了华北平原冬小麦(Triticum aestivum)的光响应数据和气孔导度数据。拟合结果表明: 推导的气孔导度机理模型较之Ball-Berry气孔导度模型和Tuzet等气孔导度模型, 能更好地描述冬小麦的气孔导度与净光合速率之间的关系。如果用气孔导度的机理模型耦合光合作用对光响应的修正模型, 则耦合模型可以很好地描述华北平原冬小麦叶片气孔导度对光强的响应曲线, 并可直接估算冬小麦的最大气孔导度和对应的饱和光强, 同时可以研究最大气孔导度是否与最大净光合速率同步的问题。拟合结果还表明: 冬小麦在30 ℃、560 μmol·mol^-1CO₂, 或在32 ℃、370 μmol·mol^-1CO₂条件下, 最大气孔导度与最大净光合速率并不同步。     

羊草气孔导度的Jarvis-类模型

在干旱半干旱气候条件下,土壤水分状况通常是决定植物气孔导度的重要因素,现有气孔导度模型Jarvis-类和耦合模型(或光合-导度模型)未充分考虑这一因素对气孔导度的影响。本文以Jarvis气孔导度模型为基础,提出一个充分考虑土壤水分状况因素的气孔导度模型。该模型对羊草连续两年(1998~1999)野外实地观测结果拟合良好(R2=0.603),预测能力较线性回归方程(R2=0.361)有明显提高。     

最优气孔行为理论和气孔导度模拟

气孔调节功能是陆地生态系统碳-水耦合过程中最重要的环节。与即时的气孔导度测量相比, 气孔导度斜率能有效地反映气孔导度对CO₂浓度、饱和水汽压亏缺和光合作用的敏感性, 包含了环境因子对光合作用和临界水分利用效率等的综合影响, 为研究全球变化下陆地生态系统碳-水耦合关系提供了一个简明且综合的框架。气孔导度模型从经验模型、半经验模型发展到机理模型, 经过很多学者的改进, 但是模型参数的生物学意义和变化规律还不明确。鉴于气孔导度斜率方面研究的重要性和研究的不足, 为了加强对气孔导度调节规律的认识, 并减少气孔导度模拟的不确定性, 该文主要综述了长期以来国内外关于最优气孔行为理论和气孔导度模拟方面的研究成果, 其中包括广泛使用的气孔导度模型及参数意义, 讨论影响气孔导度斜率的主要因素以及气孔导度机理模型的应用, 并对最优气孔行为理论和气孔导度模拟方面的研究做了简单展望。     

植物气孔导度对CO2响应模型的构建

构建一个普适性的植物叶片气孔导度(g_s)对CO₂浓度响应(g_s-C_a)的模型, 对定量研究植物叶片g_s对CO₂浓度的响应变化尤为必要。该研究运用便携式光合仪(LI-6400)测量了大豆(Glycine max)和小麦(Triticum aestivum)光合作用对CO₂的响应曲线(A_n-C_a), 在比较传统的Michaelis-Menten模型(M-M模型)和叶子飘构建的CO₂响应模型拟合大豆和小麦A_n-C_a效果的基础上, 构建了g_s-C_a响应新模型。然后用新构建的模型拟合大豆和小麦的g_s-C_a曲线, 并将拟合结果与传统模型的拟合结果, 以及与其对应的观测数据进行比较, 以判断所构建模型是否合理。结果显示: 叶子飘构建的A_n-C_a模型可较好地拟合大豆和小麦的A_n-C_a曲线, 确定系数(R²)均高达0.999。M-M模型拟合大豆和小麦的A_n-C_a曲线时的R²虽然也较高, 但在较高CO₂浓度时的拟合曲线偏离观测曲线。因此, 基于叶子飘的A_n-C_a模型构建g_s-C_a模型更为可行。新构建的g_s-C_a模型可较好地拟合大豆和小麦的g_s-C_a曲线, R²分别为0.995和0.994, 而且还可以直接给出最大气孔导度(g_s-max)、最小气孔导度(g_s-min), 以及与g_s-min相对应的CO₂浓度值(C_s-min)。拟合得到大豆和小麦的g_s-max分别为0.686和0.481 mol·m^-2·s^-1, 与其对应的观测值(分别为0.666和0.471 mol·m^-2·s^-1)之间均不存在显著差异; 同样, 拟合得到的大豆和小麦的g_s-min分别为0.271和0.297 mol·m^-2·s^-1, 与其对应的观测值(分别为0.279和0.293 mol·m^-2·s^-1)之间也均不存在显著差异; 此外, 新构建的g_s-C_a模型给出大豆和小麦的C_s-min值分别为741.45和1 112.43 μmol·mol ^-1, 与其对应的观测值(732.78和1 200.34 μmol·mol ^-1)也不存在显著差异。由此可见, 该研究新构建的g_s-C_a模型可作为定量研究植物叶片气孔导度对CO₂浓度变化的有效数学工具。     

冬小麦叶片气孔导度模型水分响应函数的参数化

植物气孔导度模型的水分响应函数用来模拟水分胁迫对气孔导度的影响过程, 是模拟缺水环境下植物与大气间水、碳交换过程的关键算法。水分响应函数包括空气湿度响应函数和土壤湿度(或植物水势)响应函数, 该研究基于田间实验观测, 分析了冬小麦(Triticum aestivum)叶片气孔导度对不同空气饱和差和不同土壤体积含水量或叶水势的响应规律。一个土壤水分梯度的田间处理在中国科学院禹城综合试验站实施, 不同水分胁迫下的冬小麦叶片气体交换过程和气孔导度以及其他的温湿度数据被观测, 同时观测了土壤含水量和叶水势。实验数据表明, 冬小麦叶片气孔导度对空气饱和差的响应呈现双曲线规律, 变化趋势显示大约1 kPa空气饱和差是一个有用的阈值, 在小于1 kPa时, 冬小麦气孔导度对空气饱和差变化反应敏感, 而大于1 kPa后则反应缓慢; 分析土壤体积含水量与中午叶片气孔导度的关系发现, 中午叶片气孔导度随土壤含水量增加大致呈现线性增加趋势, 但在平均土壤体积含水量大于大约25%以后, 气孔导度不再明显增加, 而是维持在较高导度值上下波动; 冬小麦中午叶片水势与相应的气孔导度之间, 随着叶水势的增加, 气孔导度呈现增加趋势。根据冬小麦气孔导度对空气湿度、土壤湿度和叶水势的响应规律, 研究分别采用双曲线和幂指数形式拟合了水汽响应函数, 用三段线性方程拟合了土壤湿度响应函数和植物水势响应函数, 得到的参数可以为模型模拟冬小麦的各类水、热、碳交换过程采用。     

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).     

半干旱地区3种植物叶片水平的抗旱耐旱特性分析——两个气孔导度模型的应用和比较

在对半干旱区3种植物进行生理生态特性测定的基础上,应用两种气孔导度模型进行参数的非线性拟合,BBL模型平均可以解释77.6%的结果,Gao模型平均可以解释59.3%的结果。但Gao模型作为一个机理性的模型,其参数具有明确的物理意义。模型的行为和敏感性分析结果说明,用BBL计算的气孔导度一般大于Gao模型。BBL模型对于干旱胁迫下的土壤水分亏缺没有响应, 因而不适合用作干旱半干旱区的植物生理生态学分析和生态系统模拟。而Gao模型可以描述在各种水分条件下植物气孔导度的响应。Gao模型的结果说明,与油松 (Pinus tabulaeformis) 和中间锦鸡儿 (Caragana intermedia) 比较,小叶杨 (Populus simonii) 具有最小的抗旱和耐旱能力,油松具有最好的叶片水平的耐旱和抗旱特性,但其气孔导度对土壤水分的不敏感意味着在干旱条件下维持光合作用的同时,也可能会导致过多的水分损失。中间锦鸡儿具有很强的耐旱性,且其气孔导度对土壤水分的变化敏感,二者相结合,中间锦鸡儿可以在土壤水分条件较好的情况下,维持较大的气孔导度以满足光合作用的需要,但在土壤水分胁迫严重的时候能迅速降低气孔导度以保持土壤水分。     

黄土高原油松冠层气孔导度和蒸腾变化特征与模拟

油松是黄土高原重要的造林树种,模拟其冠层气孔导度和蒸腾对区域水量平衡计算和人工林可持续经营具有重要意义。基于2015—2018年TDP(Thermal dissipation probes)方法所测得液流数据,分析了黄土高原地区油松冠层平均气孔导度(g_c)与冠层蒸腾(Tr)的变化特征与影响因素,并采用Penman-Monteith公式和Jarvis型气孔导度模型模拟了其g_c和Tr的变化过程,结果表明：(1)该地区油松g_c和Tr日内变化均呈现单峰型,日均蒸腾耗水量为(1.25±0.57) mm/d,生长季(4—10月)总蒸腾耗水量均值为195.47 mm。(2)g_c的日内变化受太阳辐射(Rad)驱动(偏相关系数为0.65),当Rad高于300 W/m²时,驱动作用减弱;g_c的日内变化受水汽压亏缺(VPD)控制(偏相关系数为-0.41),随VPD的增加而降低;g_c的日际变化受土壤水分限制(偏相关系数为0.46),当根区相对有效含水率(RE...     

羊草叶片气孔导度对环境因子的响应模拟

准确定量描述植物气孔对环境的响应是了解植物光合作用机理、预测植物生产力及其大气－植被－土壤系统中水分和热量交换的关键。利用松嫩平原盐碱化草地羊草光合生理特征的野外观测数据,分析了羊草叶片气孔导度对环境因子的反应,结果表明：羊草叶片气孔导度对环境因子变化敏感,尤其对瞬时光合有效辐射（ＰＡＲ）、叶片与空气间的水汽压亏损（ＶＰＤ）和空气温度（Ｔａ）反应十分明显。依据野外实测资料对国际上两类代表性气孔导度     

光合作用-蒸腾作用-气孔导度的耦合模型及C_3植物叶片对环境因子的生理响应(英文)

以叶片的气体传输过程为基础,将蒸腾作用包括在以往光合作用气孔导度的耦合模型中,建立了光合作用蒸腾作用气孔导度的耦合模型。该模型可以模拟边界层导度对生理过程的影响。模拟了Ｃ３植物叶片对环境因子,如光照、温度、湿度、边界层导度和ＣＯ２浓度等的生理响应（光合作用、蒸腾作用、气孔导度）以及Ｃｉ和水分利用效率的变化。在环境因子变化于较大范围的情况下,模拟结果符合许多实验结论。     

Seasonal variation in stomatal conductance and physiological factors observed in a secondary warm-temperate forest

This study quantified stomatal conductance in a CO₂-fertilized warm-temperate forest. The study considered five items: (1) the characteristics of the diurnal and seasonal variation, (2) simultaneous measurements of canopy-scale fluxes of heat and CO₂ and the normalized difference vegetation index (NDVI), (3) the stomatal conductance of sunlit and shaded leaves, (4) a stomatal conductance model, and (5) the effects of leaf age on stomatal conductance. Sampled plants included evergreen and deciduous species. Stomatal conductance, SPAD, and leaf nitrogen content were measured between March and December 2001. Sunlit leaves had the largest diurnal and seasonal variation in conductance in terms of both magnitude and variability. In contrast, shaded leaves had only low conductance and slight variation. Stomatal conductance increased sharply in new shooting leaves of Quercus serrata until reaching a maximum 2 months after full leaf expansion. The seasonal changes in the canopy-scale heat and CO₂ fluxes were similar to the change in the canopy-scale NDVI of the upper-canopy plants. These seasonal changes were correlated with the leaf-level H₂O/CO₂ exchanges of upper-canopy plants, although these did not represent the stomatal conductance in fall completely. Seasonal variations in the leaf nitrogen content and SPAD were similar, except leaf foliation, until day 130 of the year, when the behaviors were completely the opposite. A Jarvis-type model was used to estimate the stomatal conductance. We modified it to include SPAD as a measure of leaf age. The seasonal variation in stomatal conductance was not as sensitive to SPAD, although estimates for evergreen species showed improvements.     

极端干旱区多枝柽柳叶片气孔导度的环境响应模拟

气孔通过调节植物体水分散失和CO₂吸收在植物适应环境变化和环境胁迫中发挥重要作用。该文在对极端干旱区多枝柽柳(Tamarix ramosissma)叶片气体交换参数观测的基础上, 引入诊断函数f(H)对BWB模型和BBL模型提出的气孔导度(g_s)模型中的空气湿度(h_s或D_s)进行了评价, 并将评价结果引入叶子飘和于强推导出的g_s机理模型。结果表明: (1) BWB和BBL模型对h_s (或D_s)的模拟效果存在很大差异: BWB模型拟合效果较好(R² = 0.5354), BBL模型的结果显著但效果较差(R² = 0.1103)。试验结果显示: 随h_s(或D_s)的增大, g_s呈先增大后减小的趋势, 可用Gauss模型进行拟合, R²分别为0.593和0.258, 说明g_s与h_s的关系要比D_s更密切; (2)叶子飘和于强给出的简化模型(Simple模型)和该文给出的指数模型(Gauss-h模型)均具有较好的模拟效果(R²分别为0.8707和0.8286), η值分别为0.1245和0.0171, 其值均介于0-1之间; (3)模型验证中Gauss-h模型较Simple模型明显低估了观测值, 当观测条件无限趋近于Simple模型的假设时, Simple模型的拟合效果可得到显著提高(R² = 0.9606)。     

环境因子对常绿阔叶树种脱耦联系数及冠层气孔导度估算的影响

精确模拟冠层气孔导度(G_S)对于评估区域蒸散具有重要意义。该研究选择两种常见的人工阔叶树种尾叶桉(Eucalyptus urophylla, 外来种)和木荷(Schima superba, 本地种)作为研究对象, 利用K?stner法和修订的Penman-Monteith公式计算冠层平均气孔导度(分别定义为G_S1和G_S2)。研究还分析了环境因子对冠层脱耦联系数(Ω)的影响, 并用其来评价两种方法模拟的冠层气孔导度的合理性。结果表明, 两个树种冠层气孔导度均与气象条件耦合较好(尾叶桉: Ω = 0.10 ± 0.03, 木荷: Ω = 0.17 ± 0.03)。主成分分析显示, 光合有效辐射(PAR)以及水汽压亏缺(D)显著影响Ω的大小, 而风速(u)的影响较小。单因素分析则发现各环境因子与Ω之间的相关性并不显著。边界线分析表明D和PAR的增加使得Ω最终趋向于一个与树种有关的稳定值(木荷≈ 0.20, 尾叶桉≈ 0.05), 而Ω随u的增加呈幂指数下降。与木荷相比, 尾叶桉具有更高的气孔导度(尾叶桉和木荷的G_S2年平均值分别为(33.42 ± 9.37) mmol·m ^-2·s ^-1和(23.40 ± 2.03) mmol·m ^-2·s ^-1), 并且尾叶桉和木荷的G_S1与G_S2的线性拟合斜率分别为0.92 (R ² ≈ 0.70)和0.98 (R ² ≈ 0.76) , 表明G_S1比G_S2高估了冠层气孔导度。另外, G_S1和G_S2对水汽压亏缺的敏感性与参比气孔导度(G_Siref, D = 1 kPa时的气孔导度)的比值Pi与Ω紧密相关。根据统计, 尾叶桉和木荷的G_S1估计值在Ω = 0.05-0.15 (83.1%的数据)和0.10-0.20 (47.8%的数据)之间时是相对可靠的。     

Ozone‐induced stomatal sluggishness changes stomatal parameters of Jarvis‐type model in white birch and deciduous oak

• Stomatal ozone flux is closely related to ozone injury to plants. Jarvis‐type multiplicative model has been recommended for estimating stomatal ozone flux in forest trees. Ozone can change stomatal conductance by both stomatal closure and less efficient stomatal control (stomatal sluggishness). However, current Jarvis‐type models do not account for these ozone effects on stomatal conductance in forest trees.
• We examined seasonal course of stomatal conductance in two common deciduous tree species native to northern Japan (white birch: Betula platyphylla var. japonica ; deciduous oak: Quercus mongolica var. crispula ) grown under free‐air ozone exposure. We innovatively considered stomatal sluggishness in the Jarvis‐type model using a simple parameter, s , relating to cumulative ozone uptake (defined as POD : phytotoxic ozone dose).
• We found that ozone decreased stomatal conductance of white birch leaves after full expansion (?28%). However, such a reduction of stomatal conductance by ozone fell in late summer (?10%). At the same time, ozone reduced stomatal sensitivity of white birch to VPD and increased stomatal conductance under low light conditions. In contrast, in deciduous oak, ozone did not clearly change the model parameters.
• The consideration of both ozone‐induced stomatal closure and stomatal sluggishness improved the model performance to estimate stomatal conductance and to explain the dose–response relationship on ozone‐induced decline of photosynthesis of white birch. Our results indicate that ozone effects on stomatal conductance (i.e . stomatal closure and stomatal sluggishness) are crucial for modelling studies to determine stomatal response in deciduous trees, especially in species sensitive to ozone.

     

Diurnal patterns of chlorophyll a fluorescence and stomatal conductance in species of two types of coastal tree vegetation in southeastern Brazil

 Diurnal measurements of chlorophyll fluorescence parameters and stomatal conductance to water vapour were carried out in five woody species and a bromeliad from two coastal vegetation types in Brazil, the rock outcrop of Pao de Acúcar and the sand dunes of Macaé. The environmental conditions of both study sites are characterized by high temperatures and light levels. The studied species comprised C₃ plants with different degrees of stomatal closure during the day, overall daily stomatal conductance and a plant with a typical CAM pattern. Plants on Pao de Acúcar exhibited only a small decline in potential quantum yield throughout the day. The non-photochemical quenching and the approximate photosynthetic electron transport rates were maximal during the peak of irradiance. In Macaé, light response curves of fluorescence parameters in the CAM-tree Clusia hilariana showed a clear differentiation between phases III and IV of CAM. In phase III, decarboxylation of organic acids probably maintained high internal CO₂ levels and there was only a small decrease in photochemical quenching with saturating light levels. In phase IV, the depletion of the organic acid pool and low stomatal conductances resulted in much lower levels of effective quantum yield and a substantial increase in both 1-q_P and non-photochemical quenching with increasing light levels. This behaviour during phase IV in the CAM-tree C. hilariana was comparable to the performance of the C₃-Clusia C. aff parviflora at Pao de Acúcar. It is seen that both the C₃ species and the CAM tree occurring in the two coastal communities effectively adjust their photochemical efficiency to environmental conditions and especially to diurnal variations of stress. Received: 29 April 1996 / Accepted: 14 November 1996     

气孔导度模型在北方农牧交错带的适用性评价——以马铃薯和油葵为例

基于北方农牧交错带主要作物马铃薯和油葵的叶片气孔导度、净光合速率和气象因子的平行观测数据,对常用气孔导度模型(Jarvis模型、Ball-Berry模型、Leuning模型和Medlyn模型)进行了适用性评价.结果表明:马铃薯的气孔导度与净光合速率呈现较强的线性关系,而油葵气孔导度与净光合速率的线性关系较弱.对于马铃薯气孔导度,Ball-Berry模型模拟效果最佳,Leuning模型和Medlyn模型次之,Jarvis模型模拟效果最差;各模型的模拟值与观测值的均方根误差(RMSE)分别为0.0331、0.0371、0.0456和0.0794 mol·m^-2·s^-1,归一化均方根误差(NRMSE)分别为26.8%、30.0%、36.9%和64.3%,拟合度(R²)分别为0.96、0.61、0.91和0.88.对于油葵的气孔导度,Jarvis模型模拟效果略好于Ball-Berry模型、Medlyn模型和Leuning模型,其RMSE分别为0.2221、0.2534、0.2547和0.2758 mol·m^-2·s^-1,NRMSE分别为40.3%、46.0%、46.2%和50.1%,R²分别为0.38、0.22、0.23和0.20.气象因子对气孔导度作用的通径分析表明,北方农牧交错带马铃薯和油葵气孔导度日变化主要受饱和水汽压差影响.模型评价结果表明用于油葵的气孔导度模型需要进一步改进.     

Simulation of the stomatal conductance of winter wheat in response to light, temperature and CO2 changes

BACKGROUND AND AIMS: The stomata are a key channel of the water cycle in ecosystems, and are constrained by both physiological and environmental elements. The aim of this study was to parameterize stomatal conductance by extending a previous empirical model and a revised Ball-Berry model. METHODS: Light and CO(2) responses of stomatal conductance and photosynthesis of winter wheat in the North China Plain were investigated under ambient and free-air CO(2) enrichment conditions. The photosynthetic photon flux density and CO(2) concentration ranged from 0 to 2000 micro mol m(-2) s(-1) and from 0 to 1400 micro mol mol(-1), respectively. The model was validated with data from a light, temperature and CO(2) response experiment. RESULTS: By using previously published hyperbolic equations of photosynthetic responses to light and CO(2), the number of parameters in the model was reduced. These response curves were observed diurnally with large variations of temperature and vapour pressure deficit. The model interpreted stomatal response under wide variations in environmental factors. CONCLUSIONS: Most of the model parameters, such as initial photon efficiency and maximum photosynthetic rate (P(max)), have physiological meanings. The model can be expanded to include influences of other physiological elements, such as leaf ageing and nutrient conditions, especially leaf nitrogen content.     

Correlations of stomatal conductance with hydraulic and chemical factors in several deciduous tree species in a natural habitat

Recent research in whole-plant stomatal physiology, conducted largely with potted plants in controlled environments, suggests that stomatal conductance ( g _s) might be more closely linked to plant chemical variables than to hydraulic variables. To test this in a field situation, seasonal g _s was examined in relation to a number of plant and environmental variables in 11 temperate, deciduous forest tree species. Stomatal conductance was generally better correlated with environmental variables (air temperature, vapor pressure deficit, PPFD) than with plant variables, and slightly better correlated with plant hydraulic variables (shoot water and osmotic potentials) than with plant chemical variables (xylem sap ABA concentration, xylem sap pH). We examined a model, developed previously for maize, which describes regulation of g _s by xylem sap ABA concentration with leaf water status acting to modify stomatal sensitivity to the ABA signal. This model explained slightly more variation in seasonal g _s in the forest trees than did single plant variables but not more variation than most single environmental variables. Response surface models, especially those incorporating environmental variables, were more consistently successful at explaining g _s across species.     

赣西三市热环境时空演变特征及影响因素

以赣西三市为研究区域, 采用2002、2016年2个时段的TM/OLI/TIRS影像数据, 获得辐射亮度温度和土地利用/覆被分类数据, 借此分析热环境时空演变特征、热力景观格局指数变化以及影响热环境演变的因素, 旨在为改善赣西城市热环境问题提供科学的依据。结果表明: 随着城市化发展, 近15年(2002—2016年)来, 赣西三市热岛效应明显增强, 但不同区域发展程度有所不同, 热岛效应强度总体增加的趋势为: 萍乡 > 宜春 > 新余; 从热环境分布来看, 三市南部地区低温与次低温面积范围相对较多, 且呈现扩大趋势; 从热环境景观格局演变来看, 三市的中温区斑块优势度降低明显, 破碎化程度加强, 宜春和新余市区次低温与次高温斑块优势增多并且有形成大斑块的趋势; 从热环境贡献指数来看, 建设用地对热环境贡献最大, 水体和林地则对城市热岛效应有显著的抑制作用。