【作者】 李静；

【导师】 李小明；

【作者基本信息】 山东大学 ， 环境科学， 2014， 博士

【摘要】 植物叶片的气孔在调节气体交换方面具有重要作用,他们控制着水分的流通和CO2的摄入。光照、温度、水分供应、大气CO2浓度以及植物激素等环境因子影响了气孔的行为,包括气孔的密度、气孔孔径和气孔开闭等。而这些因素进而影响了植物叶片对气体交换的调节能力。植物不仅通过进化具有能够适应全球气候变化的策略和机制,而且植物也在影响和推动着全球气候变化。植物叶片气孔行为是植物生理生态研究的热点问题,自上世纪七十年代以来,已有不少学者提出了叶片气孔导度对环境因子响应的气孔导度模型。发展至今,描述气孔导度的数学模型主要分为两大类。一类是经验模型,另一类模型是优化气孔导度模型。目前的研究结果普遍认为,叶片气孔导度与大气湿度或大气饱和蒸汽压差之间的关系主要表现为,当大气相对湿度下降或大气蒸汽压差升高时气孔导度逐渐降低,并且这种相关性呈现单一的变化趋势。气孔导度的模型虽然不断的被提出或修改,模型中叶片气孔导度(gs)与大气相对湿度(RH)/水汽压亏缺(VPD)之间的本质关系仍然呈单一的正相关/负相关。然而,近期的一些研究结果却发现,现在普遍流行的气孔导度模型,如Jarvis模型、BWB (Ball-Woodrow-Berry)模型和Leuning模型的模拟结果与实际测定结果均存在较大偏差。不少学者发现许多植物(花旗松和法国冬青等)的叶片气孔导度对VPD的响应表现出一个特别的响应特征,即单峰曲线的响应特征。除了环境因子对叶片气孔的功能产生影响,植物的内源激素也参与了叶片气孔对VPD的响应,例如脱落酸、赤霉素和吲哚乙酸等。由于叶片中脱落酸能够影响气孔的开闭,因此作为叶片气孔对环境因子(特别是逆境)响应的内在因素,脱落酸是目前研究植物叶片气孔对环境因子响应的热点。对于控制气孔功能,吲哚乙酸和赤霉素与脱落酸具有拮抗作用。本文研究了山东省济南市及新疆维吾尔自治区的乌鲁木齐市和吐鲁番市的多种落叶阔叶树种(白蜡树,新疆杨,毛白杨,胡杨,山樱花,日本晚樱,美洲黑杨I-107,欧美杨I-69,白玉兰,木瓜海棠,银杏,二球悬铃木,红叶樱桃李和银白杨)的叶片气体交换对水汽压亏缺的响应特征。比较了不同气候区在2010年8月份的四种植物(白蜡树,新疆杨,毛白杨,胡杨)的叶片气体交换对水汽压亏缺的响应特征,以及济南地区3种植物(白蜡树,新疆杨,毛白杨)在2010年三个季节(初夏、仲夏和晚秋)的气体交换对水汽压亏缺的响应特征,同时测定了4种植物(白蜡树,新疆杨,毛白杨,胡杨)的3种植物酸性激素(GA3, IAA和ABA),主要研究结果如下：1)对三个不同的气候区(山东省济南市,典型暖温带湿润／半湿润气候；新疆维吾尔自治区乌鲁木齐市,温带大陆荒漠干旱气候；新疆维吾尔自治区吐鲁番市,极端荒漠气候)的四种植物(白蜡树、新疆杨、毛白杨和胡杨)叶片气孔导度对VPD的响应研究发现：随着VPD的升高,植物叶片的气孔导度先升高后降低；在VPD的某个范围内,气孔导度达到一个最大值(gs-max);四种植物叶片气孔导度对VPD的响应模式在三个气候区均表现出了相似的响应特征。叶片气孔导度对VPD的响应曲线可以使用对数正态分布模型来描述(gs=a·exp(-0.5(ln(D/c)/b)2), D=VPD, R2=0.845-0.996)。植物叶片气孔导度出现最大值时的VPD/RH (gs-max-VPD/RH)可以通过模型的拟合结果计算得出,结果显示在温度相差不大的月份(8月),测定植物叶片气孔导度出现最大值的RH值(gs-max-RH)与所处生境的植物生长期(4月-10月)的平均相对湿度相关(R2>0.71)：即在大气平均湿度高的地区,植物在高RH范围内出现gs-max;反之,在大气平均相对湿度低的地区,植物在低RH范围出现gs-max。根据气孔的最优化理论,对应于最大气孔导度的VPD/RH可称之为优化的VPD/RH。对植物在一定的VPD范围内测定的气孔导度数据进行均方根误差(Root Mean Square Error, RMSE, σ)的检验,σ的大小代表了叶片气孔导度对VPD响应敏感度的强弱。对四种植物叶片的三种内源激素(赤霉素,GA3；脱落酸,ABA；吲哚-3-乙酸,IAA)进行定量分析后可知,植物叶片气孔导度对VPD变化的敏感度与ABA浓度有关：ABA浓度越高,gs对VPD响应越敏感；ABA浓度越低,gs对VPD的响应越不敏感。这说明叶片的ABA水平可以作为气孔对VPD响应敏感度的指示之一。在VPD变化的过程中,济南地区的三种植物净光合速率(An)变化不大,说明此地区的三种植物A。对VPD响应不敏感。乌鲁木齐和吐鲁番市的3种植物的A。则随着VPD的升高而逐渐增大。三个地区的四种植物,其蒸腾速率(E)则均随着VPD的增加而逐渐增大。吐鲁番市植物的An和E增加的最为明显,这与此地植物的高GA3和IAA的含量以及高的GA3/ABA和IAA/ABA有关。四种植物的水分利用效率在三个不同气候区没有出现显著差异。对比在三个地区均有自然生长的白蜡树的测定结果,说明白蜡树在极端干旱的气候条件下能够表现出较好的气孔控制能力。同时,两种代表性的气孔导度模型对实验数据进行了模拟,并与实测值进行了比较。结果发现目前流行的经验模型(Leuning气孔导度模型)和优化气孔导度模型均无法较好的拟合本实验的测定结果。2)对济南地区3种植物(白蜡、新疆杨、毛白杨)进行的叶片气孔导度对VPD响应的季节变化(2010年6月初夏、8月仲夏、10月晚秋)的研究结果发现,随着VPD的逐渐增大,植物叶片气孔导度先升高,达到一个最大值(gs-max)后,再降低。三种植物在三个季节均表现出了这种气孔导度对VPD的响应特征。叶片气孔导度对VPD的响应,可用对数正态分布模型来描述(gs=a·exp(-0.5(ln(D/c)/b)2), D=VPD,R2=0.838-0.995了。三种植物在三个季节均表现出了较好的模拟效果,说明此三种植物的生长均存在一个优化的VPD/RH范围。这个优化值,可以通过对数正态分布模型的拟合结果计算得出。三个月份多年平均温度差异明显,降水量均较充足,各月多年平均空气相对湿度均高于55%。在大气相对湿度不是植物生长的限制性因子时,监测数据显示植物叶片气孔导度最大值所对应的RH (gs-max-RH)是与监测月份的平均温度有关(R2>0.81)：即在平均温度高的月份,植物在高RH范围内出现gs-max;在平均温度低的月份,植物在低RH范围内出现gs-max。本实验使用经验模型(Leuning气孔导度模型)和优化气孔导度模型对实验数据进行了模拟,结果发现模拟值与实测值偏差较大。因此这两类模型依然不能很好的解释本实验的测定结果。对三种植物叶片的三种内源激素(GA3、ABA、IAA)进行定量分析后可知,不同季节的植物叶片气孔导度对VPD响应的敏感度与ABA浓度有关：ABA浓度越高,gs对VPD响应越敏感；ABA浓度越低,gs对VPD的响应越不敏感。敏感度的检验依然使用RMSE。随着VPD的逐渐升高,三种植物在三个月份的净光合速率的变化特征均未受到VPD的影响。这说明在降水充足地区生长的植物,其光合速率对VPD变化不敏感。但三种植物的蒸腾速率均随着VPD的升高而逐渐升高。水分利用效率(WUE)的变化特征与不同气候区植物的研究特征一致：随着VPD的逐渐升高,WUE逐渐下降。十月份时白蜡叶片叶绿素含量的显著降低,说明叶片出现了衰老。这个结果很好的解释了白蜡树在十月份时叶片气孔导度最大值所对应的RH显著降低的结果。3)本实验同时对济南地区10种落叶乔木的叶片气体交换对VPD的响应进行了研究(2009-2013年4-5月)。结果显示,10种植物叶片的气孔导度对VPD的响应特征,均符合单峰型的特征曲线,即随着VPD的变化,气孔导度先升高后降低。使用对数正态分布模型对10种植物叶片气孔导度对VPD的响应曲线进行模拟(gs=a·exp(-0.5(ln(D/c)/b)2), D=VPD, R2=0.885-0.987),得到了很好的拟合结果。这不仅证明我们对不同气候区植物的结论的正确性,也说明季节变化中3种植物的实验结果是正确的。结合上述各项结论可知,植物的生长存在一个优化的大气相对湿度(或水汽压亏缺),当大气环境中大气相对湿度(或水汽压亏缺)高于或低于此优化湿度(或水汽压亏缺)时,气孔导度即减小。多种植物的研究结果显示,植物叶片气孔导度对VPD的这种响应特征具有普遍性。同时,本研究发现当植物生长的限制性环境因子为大气相对湿度,而不是温度时(在适宜的温度调节下),植物叶片出现最大气孔导度所对应的RH值(gs-max-RH)与所处生境的植物生长期(四月-十月)的平均相对湿度相关(R2>0.71)；当大气湿度适宜,温度成为植物生长的限制性因子时,植物叶片出现最大气孔导度所对应的RH值(gs-max-RH)与监测月份的平均温度有关(R2>0.81)。同时,植物激素很好的调节了叶片的气孔功能。气孔导度模型被经常用来模拟植物的气孔对环境因子的响应,预测全球植物的产量以及了解植物气孔响应对全球气候变化的影响。本文的研究结果显示,气孔导度对VPD/RH的响应使用目前普遍流行的气孔导度模型来模拟仍然是不全面的。并且使用这些模型进行全球植物产量的预测及研究植物对全球气候变化影响的模拟结果可能也是不准确的。因此,我们可能需要一个更加完善的、能够融合本研究结果的气孔导度模型。同时,植物叶片气孔导度对VPD响应的这种单峰特征曲线的响应机理亦是进一步研究的重点。更多还原

【Abstract】 Stomata of leaves play a fundamental role in both acquiring carbon and limiting water loss. Stomatal conductance (gs) is influenced by light, temperature, water supply and the stomatal opening of closing is regulated by phytohormones. Plants have developed advanced strategies and mechanisms through evolution to adapt to local and global environmental changes by compromising photosynthesis and transpiration, and they also affect and promote local and global changes.Stomatal behavior of plant is a hot topic of research on plant physiological ecology. A number of models on stomatal conductance response to different environmental factors have been developed since1970’s. The main stomatal models until now could be divided into two types. One is empirical model, The other type of stomatal model is based on the theory of optimal stomatal behavior. The prevailing pattern regarding the relationship between gs and atmospheric water content is that increasing vapor pressure deficit (VPD) or decreasing relative humidity (RH) lead to reduction of gs. Although different stomatal conductance models are proposed or modified continuously, the essential relationship between gs and VPD (or RH) does not change. Some of present stomatal conductance models had shown poor function compared with measured data. For example, Jarvis’ model and Ball-Woodrow-Berry (BWB) model poorly predated values of gs under high RH condition,and Leuning model may not be appropriate for measured data analysis and ecosystem simulation applications in arid and semiarid zones by comparing the predicted data with measured data of three major species in a semi-arid site. Pseudotsuga menziesii and Selaginella bryopteris et al.showed one top lines’pattern of gs to VPD. All these findings showed diverse and different response patterns of gs to VPD.The response of stomata to environmental and physiological factors is complex. The phytohormone is the important factor to affect stomatal regulation, like abscisic acid (ABA), indole-3-acetic acid (IAA) and Gibberellins (GAS). Increased level of ABA when plant is under stress promotes stomatal closure and/or inhibits stomata opening in order to avoid excess water loss. The other phytohormone, including IAA and GAs are known to antagonize the effects of ABA on stomatal behavior.In this study, the responsive patterns of stomatal conductance to air humidity in three contrasting sites in China:Jinan (N36°35’-36°40’, E116°54’-117°02’), Shandong Province; Turpan (N41°12’-43°40’,E87°16’-91°55’) and Urumqi (N42°45’-45°00’, E86°37’-88°58’) in Xinjiang Uygur Autonomous Region. More than10temperate tree species were measured, including(Fraxinus chinensis Roxb., Populus alba L. var. pyramidalis Bge., Populus tomentosa Carr., Populus euphratica, Cerasus serrulata (Lindl.) G. Don ex London, Prunus serrulata var. lannesiana (Carr.) Rehd., Populus x euramericana ’Neva’, Populus deltoides, Magnolia denudata Desr., Chaenomeles cathayensis (Hemsl.) Schneid., Ginkgo biloba Linn., Platanus x acerifolia(Ait.) Willd., Prunus cerasifera Ehrhar f. atropurpurea (Jacq.) Rehd, Populus alba Linn.). Four tree species (F chinensis, P. alba var., P. tomentosa, P. euphratica) were measured to research the response patterns of stomatal conductance to VPD under very different climate conditions (Jinan, Urumqi, Trupan). Three tree species (F. chinensis, P. alba var., P. tomentosa) were measured to research the response patterns of stomatal conductance to VPD in different seasons (early summer, midsummer, late autumn). Meanwhile, three kinds of phytohormones (abscisic acid, ABA; gibberellic acid, GA3; indole-3-acetic acid, IAA) in leaves of four tree specie (F. chinensis, P. alba var., P. tomentosa, P. euphratica) in three sites were also measured with high performance liquid chromatography. In addition, the two stomatal models (Leuning model and the optimal stomatal model) were tested and compared between the predicted and measured stomatal conductance values in the leaves of the trees.1) Response of stomatal conductance to VPD in four species of trees (F. chinensis, P. alba var., P. tomentosa, P. euphratica) in three different climate zones (Jinan with typical warm humid/semi-humid climate, Urumqi with temperate continental arid climate, Turpan with extreme arid desert climate) were measured. The results showed that:the response of gs to a gradient, of increasing VPD in four tree species in three sites performed peak curves that could be fitted with a Log Normal Model (gs=a·exp(-0.5(ln(D/c)/b)2), D=VPD, R2=0.845-0.996) using measured data in this study. The VPD/RH values corresponding to the maximum of gs (gs-max-VPD/RH) can be calculated using the fitting models for four tree species in three sites. We found that the gs-max-VPD correlated negatively with air relative humidity in three sites during the plant growth season (April-October,2010).The test of the sensitivity of gs to VPD in four tree species in three different climate zones was carried out using Root Mean Square Error (RMSE, σ) of stomatal conductance along the gradient of increasing VPD. Some measured data was chosen to test RMSE of stomatal conductance within the same certain range of VPD in four trees in three sites. The larger a related to the higher sensitivity of gs to VPD. The test demonstrated that the sensitivity in response of gs to VPD showed positively correlation with the concentration of ABA in four trees in three sites, which implied that the ABA level in leaves could be used as one of indicators of sensitivity of stomatal response to VPD.Net photosynthesis rate (An) did not show a significant variation with increasing VPD in four tree species in Jinan, but steadily increased with increasing VPD in Xinjiang. Transpiration rates (E) in four trees remained constantly increasing following an increase in VPD in three sites. P. alba var. in Turpan has the higher An, E and gs than F. chinensis in Trupan and the four trees in the other two sites. The water use efficiency (WUE) in four trees did not show obvious difference under very different climatic conditions, especially F. chinensis could perform good control ability of the stomatal regulation even under extremely arid climate zone.The prevailing empirical model of stomatal conductance to VPD (Leuning stomatal model) and optimal stomatal behavior model could not properly simulate our measurement data with F-test.2) The role of vapor pressure deficit (VPD) in regulating leaf gas exchange of three species of trees (Fraxinus chinensis Roxb., Populus alba L. var. pyramidalis Bge. and Populus tomentosa Carr.) was investigated in Jinan, China. Experiments were performed in early summer (June), midsummer (August) and late autumn (October). Three kinds of phytohormones (GA3, IAA, ABA) in the leaves of the three trees were determined with measured gas exchange. The responses of stomatal conductance (gs) to a gradient of increasing VPD in the leaves of the three trees exhibited a peak curve under different seasons, which differed from the prevailing response pattern of gs to VPD in mostly literature. The peak curves could be fitted with a Log Normal Model (gs=a·exp(-0.5(ln(D/c)/b)2), D=VPD, R2=0.838-0.995). The VPD/RH values of corresponding maximum of gs (gs-max-VPD/RH) could be calculated by fitted models of peak curves of gs to VPD. The RH values, corresponding the gs-max, positively correlated with the mean monthly temperature (R2>0.81) in2010.Two typical stomatal models (Leuning stomatal model and the optimal stomatal model), were used to estimate gs values, and they were poorly performed the prediction of gs in three trees with F-test.The test of the sensitivity of gs to VPD in three tree species was carried out using RMSE, too. Some measured data was chosen to test RMSE of stomatal conductance within the same certain range of VPD in three trees in three seasons. The larger σ related to the higher sensitivity of gs to VPD. The test demonstrated that the concentration of ABA was positively correlated to sensitivity in response of stomatal conductance to VPD in leaves of species of trees under different seasons, which also implied that the ABA level in leaves could be used as one of indicators of sensitivity of stomatal response to VPD.Assimilation continued undiminished in spite of the declined gs at low and high VPD, which demonstrated An was not sensitive to VPD when they growed up in plentiful rainfall area. Transpiration rates (E) in three trees remained constantly increasing following an increase in VPD in three seasons, and the water use efficiency did not show obvious difference under different seasons. These results were same to the result of the first part.However, An of F.chinensis in October decreased sharply. This founding was associated with the senescence in plant leaves. The Chlorophyll concentration of F.chinensis decreased significantly in October, and it’s lower than the other trees’.3) Ten decideous tree species (C. serrulata, P. lannesiana,1-69,1-107, M. denudata, C. cathayensis, G. biloba, P. acerifolia, P. cerasifera, P. alba) were measured to study the response of gs to vapor pressure deficit in April to May,2009-2013. The result showed that the responses of gs to increasing VPD in leaves of ten trees also exhibited a peak curve, which could be fitted with a Log Normal Model (gs=a-exp(-0.5(ln(D/c)/b)2), D=VPD, R2=0.885-0.987). These results proved our findings about the one peak curve in the response of gs to VPD in different climate zones and in different seasons.Taken together, our results reveal that there is an optimal RH/VPD to plant. The stomatal conductance of leaves will decrease when RH/VPD is higher or lower than the optimal RH/VPD. The same results of more than ten tree species in the response of gs to VPD we gotted here, illustrated that this response characteristic of stomatal conductance to RH/VPD could have the universality to plant. However, this result did not conform to the current popular stomatal model of response of gs to VPD. Stomatal conductance models were widely used to simulate the response of gs to environmental factors in trees, predict the vegetation growth of the world terrestrial ecosystem, and predict the impaction on global climatic change. However, this result of the response of gs to VPD showed that the current popular models of stomatal conductance could not predict the global terrestrial vegetation productivity perfectly. The prediction of response of gs to VPD might be incomplete with the two current popular models; the prediction of the plant production in the world and global climatic change might also be inaccurate with current popular model. Therefore, a more perfect gs model which could be able to integrate this founding was needed. Meanwhile, the stomatal response mechanism of one peak curves on gs to VPD could be the focus of further research.更多还原