落叶阔叶树种维持高光效的细胞结构与生理调控机制

	落叶阔叶树种维持高光效的细胞结构与生理调控机制
	孙虎
导师	黄伟
关键词	阔叶木本植物，光合作用，叶肉导度，叶肉导度限制，叶片解剖 Broad-leaved Tree Species, Photosynthesis, Mesophyll Conductance, Mesophyll Conductance Limitation, Leaf Anatomy
摘要	光合作用是世界上最重要的生化反应。人类和其他动植物以及微生物赖以生存的能量都直接或者间接来自于光合作用。森林是陆地生态系统的主体，是自然功能最完善、最强大的资源库、基因库和蓄水库，同时对改善生态环境、维护生态平衡，起着决定性的作用。前人研究表明，落叶阔叶树种普遍具有较高的叶肉导度（gm），并以此维持恒定光照条件下较高的光合速率。然而有关落叶阔叶树种维持较高gm的细胞结构还尚不清楚。此外，在自然界中植物所面临的光照环境并不是恒定不变的，而是在风吹、云动、林窗还有树叶之间的相互遮挡等因素的影响下而时刻发生变化的，这种不断变化的光被称为波动光。波动光主要包括光强的突然降低和突然升高。光强突然降低不会对植物造成伤害，但是会降低光合速率。而当光照突然升高后，光系统II（PSII）到光系统I（PSI）处的电子会即刻增加，但是卡尔文循环的激发有迟滞性，这就会导致PSI的过度还原并产生活性氧，进而造成PSI的光损伤。由于PSI是光合电子传递的核心组分，PSI的损伤会严重影响植物光合作用、光保护和生长，严重时甚至会造成死亡。因此，波动光是影响植物生长和作物产量的重要环境因素。然而有关常绿和落叶阔叶树种在波动光条件下光合速率诱导速度的生理调控机制还尚未可知。因此，本实验从10种常绿和10种落叶阔叶树种叶片的细胞结构和应对波动光的生理调控机制入手，探究落叶阔叶树种维持较高光合效率的生物学基础。主要的研究结论如下： 1、常绿与落叶阔叶树种的净光合速率（AN）、气孔导度（gs）、gm、最大羧化速率（Vcmax）、最大电子传递速率（Jmax）、单位面积内叶绿体面向胞间空隙的面积（Sc/S）、单位面积内细胞面向胞间空隙的面积（Smes/S）、叶片厚度（LT）、栅栏组织厚度（PTT）以及较薄的叶绿体厚度（Tchlor）、细胞壁厚度（Tcw）、海绵组织厚度（STT）等性状的系统发育信号较弱（K<1），表明这些性状主要受到环境因素的影响。 2、落叶阔叶树种与常绿阔叶树种相比拥有更高的gs、gm、Vcmax和Jmax，以此来维持其较高的光合速率。 3、落叶阔叶树种较薄的LT、叶肉组织厚度（MT）、STT、下表皮角质层厚度（CTab）、Tcw，较厚的PTT及其占叶片厚度的比例（PTT/LT）、Smes/S、Sc/S以及单位面积内叶绿体和细胞面向胞间空隙面积的比值（Sc/Smes）促进了其叶肉导度的提高，进而增强其光合能力；同时，落叶阔叶树种的Sc/S、Smes/S与MT呈显著负相关，而在常绿阔叶树种中无相关性；此外，常绿和落叶阔叶树种的叶片细胞壁厚度会随着下表皮角质层厚度的增加而增加，进而增加叶片的保水能力。 4、常绿和落叶阔叶树种在波动光和稳定光照条件下都主要受到生化限制（Lb），然而落叶阔叶树种在稳定光照条件下得益于其较低的气孔导度限制（Lgs）和叶肉导度限制（Lgm），使其得以维持较高的光合速率，在波动光条件下气孔导度和叶肉导度限制进一步降低从而促进光合速率的快速响应；同时，常绿阔叶树种则在波动光诱导的初期受到严重的气孔导度与叶肉导度限制，从而延缓了光合速率的响应速度，进而降低了其光能利用效率。本研究通过对10种常绿和10种落叶阔叶树种的光合速率、气孔导度、叶肉导度、相关限制、叶片解剖结构的研究，并分析了相关参数之间的关系，揭示了落叶阔叶树种维持高光效的细胞结构和生理调控机制，为认识常绿和落叶阔叶树种在生态适应和进化过程中产生差异的原因提供了理论基础。; Photosynthesis is the most important biochemical reaction in the world. The energy on which humans and other animals, plants and microorganisms depend comes directly or indirectly from photosynthesis. Forest is the main body of the terrestrial ecosystem. It is the most perfect and powerful resource pool, gene pool and reservoir with the most natural functions. Meanwhile, it plays a decisive role in improving the ecological environment and maintaining ecological balance. Previous studies have shown that deciduous broad-leaved tree species generally have higher mesophyll conductance (gm), which can maintain higher photosynthetic rate under constant light conditions. However, the related cell-level anatomical characteristics, in particular, the distribution pattern of chloroplast, are little known. In addition, the light environment faced by plants in nature is not constant, but changes dynamically owing to variation of the solar angle, cloud movement, wind-induced leaf fluttering and shading from overlapping leaves and neighboring plants. Such fluctuations of light intensity is called fluctuating light which mainly includes suddenly decrease and increase of light intensity. A suddenly decrease in light intensity decreases photosynthetic rate without damaging plants. When the light suddenly increases, electron transport from PSII immediately increases, this rapid change in PSII electron flow is accompanied by much slower kinetics of the Calvin cycle. The resulting PSI over-reduction produces reactive oxygen species within PSI and thus causes PSI photoinhibition. Owing to the key role of PSI in regulation of photosynthetic electron flow, PSI photoinhibition strongly suppresses photosynthesis, photoprotection and plant growth, and even cause the death of the plants. Therefore, fluctuating light is an important environmental factor which will affect the growth of plants and the yield of crops. However, the physiological regulation mechanisms of the response of photosynthetic rate in evergreen and deciduous broad-leaved trees under fluctuating light conditions are still unknown. Therefore, in this study, we will explore the biological basis of maintaining higher photosynthetic efficiency in 10 evergreen and 10 deciduous broadleaved species from the perspective of leaf cell structure and physiological regulation mechanism in response to fluctuating light. The main conclusions are as follows: 1. The net photosynthetic rate (AN), stomatal conductance （gs）, gm, maximum carboxylation rate（Vcmax）, maximum electron transfer rate（Jmax）, the area of chloroplast facing the intercellular space (Sc/S), the area of a cell facing the intercellular space (Smes/S), leaf thickness (LT), palisade tissue thickness (PTT), and thinner chloroplast thickness (Tchlor), cell wall thickness (Tcw) and spongy tissue thickness (STT) of evergreen and deciduous broad-leaved tree species’ phylogenetic signals of these traits were weaker (K<1), indicating that these traits were mainly
语种	中文
	2022-05
学位授予单位	中国科学院大学
文献类型	学位论文
条目标识符	http://ir.kib.ac.cn/handle/151853/75176
专题	昆明植物所硕博研究生毕业学位论文
推荐引用方式 GB/T 7714	孙虎. 落叶阔叶树种维持高光效的细胞结构与生理调控机制[D]. 中国科学院大学,2022.

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