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气孔对土壤和空气湿度的反应及其模拟
陈 骎
Subtype博士
Thesis Advisor梁 宗 锁
2013-05
Degree Grantor中国科学院研究生院
Place of Conferral北京
Keyword土壤湿度 空气湿度 根源化学信号 水力学信号 气孔导度模型
Abstract

陆生植物在进行光合作用时通过叶片上的气孔吸入二氧化碳,但同时体内水分也
从气孔向外散逸即气孔蒸腾。对叶的水分代谢来说,蒸腾是需求,根茎输送水分是供
应。供水动力源于蒸腾对水的需求,供应受需求控制;另一方面,需求依赖供应并且
受到有限供应的制约。植物通过调控气孔导度来调控需求。土壤湿度和空气湿度是影
响气孔导度的重要环境条件。
气孔对空气湿度的反应本质上是气孔对蒸腾速率的反应,现象上可以分成三类。
Buckley等人的模型和Dewar的模型都能模拟气孔对叶表水汽压亏缺(D s )的普遍的A
类反应:在D s 逐渐增大的过程中,气孔导度随着蒸腾速率的增大线性减小。但是在
Buckley等人的模型中土壤到叶片表皮的有效水力学阻力(R)增大会使斜率绝对值增
大,而在Dewar的模型中斜率与表皮细胞到保卫细胞的水力学阻力有关,与R无关。
在这个问题上,有实验支持Buckley等人的模型。植物对土壤干旱最灵敏的适应反应
之一是气孔导度减小。根源化学信号理论和水力学信号(hydraulic signal)理论各自
都有实验依据,但都存在不足,虽然对立但是可以也应该统一起来。Buckley等人的
模型提供了一个建立全面系统的气孔导度模型的基础。
Buckley等人的模型,其核心假设是水力-主动局部反馈假说:保卫细胞对表皮上
保卫细胞紧邻区域水分状况的变化有主动调节胞内渗透压的反应。文献中以蚕豆为材
料的实验支持这一假说。但是Grantz和Schwartz以鸭跖草为材料的实验不支持这一假
说。他们把离体表皮浸泡在较高浓度的KCl溶液中,气氛为空气。本文的实验中,离
体表皮浸泡在 40 mM KCl溶液中,气氛为除去CO 2 的空气。施加渗透胁迫时,甘露醇
通过溶液替换的方式加入溶液从而始终保持除去CO 2 的空气气氛。结果表明保卫细胞
对渗透胁迫有减少胞内渗透物质积累的主动反应。ABA大幅增强这一主动反应。并且,
在ABA的作用下已张开气孔的保卫细胞对渗透胁迫有主动降低胞内渗透压的反应。这
些结果支持水力-主动局部反馈假说,并且提示在模型中引入ABA反应时,ABA应该
增强保卫细胞对表皮水势的敏感性。
Buckley等人的模型有很强的包容能力,在其基础上可以引入的因素包括:根系
和地上部ABA的合成、ABA与水力学信号的交互作用、ABA之外的其它化学信号、pH对ABA运动的影响、包括木质部栓塞在内的植株水导变化、植株体内储水等。本
文尝试在模型中引入根源ABA信号以及ABA与水力学信号的交互作用,新模型能够
模拟等水行为(isohydric behavior)和气孔对D s 的C类反应:气孔导度不随着D s 和蒸腾
速率的增大而减小。接着再引入木质部栓塞,新模型可以模拟气孔对D s 的B类反应:
气孔导度和蒸腾速率均随着D s 的增大而减小。适度的木质部栓塞还可以促进气孔关
闭,增强叶水势的稳定性。
关键词:土壤湿度,空气湿度,根源化学信号,水力学信号,气孔导度模型

Other Abstract

Terrestrial plants inhale CO 2 through stomata on leaves in photosynthesis, and
meanwhile water dissipate out of stomata as stomatal transpiration. Water consumed by
transpiration is supplied by the root and stem. The driving force for the water supply
derives from transpiration, i.e. water supply is controlled by water demand. On the other
hand, transpiration relies on water supply that is usually restricted. Plants regulate stomatal
conductance to control transpiration. Soil humidity and air humidity are two important
environmental factors relative to stomatal regulation.
Stomata respond to transpiration rate rather than air humidity per se. The model of
Buckley et al. and Dewar’s model both can model the general stomatal response to water
vapor deficit at leaf surface (D s ): stomatal conductance decreases linearly as transpiration
rate increases because of rising D s . The absolute value of the slope increases with the
effective hydraulic resistance from soil to leaf epidermis in the model of Buckley et al. In
Dewar’s model, however, the absolute value of the slope is determined by the hydraulic
resistance from epidermal cells to guard cells instead. Several researches support the model
of Buckley et al. in this regard.
The most sensitive response of plants to drought is stomatal closing. As regards the
mechanism of this response, there are two contrasting theories: the theory of root-sourced
chemical signal and that of hydraulic signal. Both of them have convincing evidence while
neither of them is complete. They should be integrated. The model of Buckley et al. offers
a basis for an integrated model of stomatal conductance.
The core hypothesis of the model of Buckley et al. is “hydro-active local feedback”:
guard cell osmotic pressure is actively regulated in response to water status in the
immediate vicinity of guard cells in the epidermis. Evidence had indicated that guard cells
of Vicia faba respond actively to osmotic stress. However, Grantz and Schwartz found that
guard cells of Commelina communis L. did not respond actively to osmotic stress in  detached epidermis. They had incubated detached epidermis in relatively high
concentration of KCl in ambient air. We incubated detached epidermis in 40 mM KCl in
CO 2 -free air. Mannitol was added by solution replacement without interrupting CO 2 -free
air. Solute accumulation in guard cells was restricted in response to osmotic stress. ABA
greatly enhanced this active response. Furthermore, ABA stimulated active response of
guard cells of initially open stomata to osmotic stress: guard cell osmotic pressure was
reduced actively. Our results support “hydro-active local feedback” hypothesis, and
suggest that ABA should enhance guard cell sensitivity to epidermal water potential if
ABA is to be introduced into the model.
The model of Buckley et al. can accommodate physiological properties concerning
stomatal regulation, such as ABA synthesis in the shoot and the root, the interaction of
ABA and hydraulic signal, some potential chemical signals, the effect of pH on the
movement of ABA, changes in the hydraulic conductance of plants including xylem
embolism, and water storage in plants. We introduced root-sourced ABA and the
interaction between ABA and hydraulic signal into the model, and successfully modeled
isohydric behavior and stomatal response to D s in Regime C. After xylem embolism was
introduced in addition, stomatal response to D s in Regime B was modeled. Simulation also
showed that moderate xylem embolism enhanced stomatal closing and the homeostasis of
leaf water potential.
Key Words:soil humidity, air humidity, root-sourced chemical signal, hydraulic signal,
model of stomatal conductance

Language中文
Document Type学位论文
Identifierhttp://ir.iswc.ac.cn/handle/361005/8964
Collection水保所知识产出(1956---)
Recommended Citation
GB/T 7714
陈 骎. 气孔对土壤和空气湿度的反应及其模拟[D]. 北京. 中国科学院研究生院,2013.
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