闽楠耐荫性随年龄和光环境变化的动态响应及分子机理

To solve the problem of regulating light environment of precious tree species Phoebe bournei plantation at different growth stages, we shall investigate the morphological and anatomic structures and ultrastructure, photosynthetic physiological characteristics of P. bournei of different ages under various light environments in nature forest. The major objectives of this project are to systematically reveal plasticity in morphological, anatomic structures and ultrastructure, physiological characteristics as well as the rules of their dynamic responses of P. bournei (including seedlings, young trees and adult trees), and find out the light-environment thresholds of the species obtaining the optimal photosynthetic productivity at different ages. By cultivation experiments of simulating different light intensities and qualities，measuring variations in morphological, physiological and endogenous hormones of P. bournei under synergistic effects of light intensity and quality, conduct difference expression analyses of genes in relation to shade tolerance and Real-time PCR analyses, to explore the combined action of light intensity and quality on modulating the phenotype of P. bournei, affecting its physiological characters and further leading to divergence of photosynthetic productivity. The results shall reveal the hormones response and molecule mechanism of P. bournei to response and adaptate light environment.In theory, this study may lay groundwork for further exploring the photoreceptor recognition of shade signal and its regulation of downstream genes. In practice, it may instruct cultivation of seedlings, regulation of light environments at different stages of constructing artificial forests, promoting its growth .

为解决珍贵用材树种闽楠人工林不同生长发育阶段的光环境调控问题，通过对天然林中不同年龄闽楠植株在不同光环境下形态、解剖结构和超微结构、光合生理特性的调查研究，旨在系统地揭示闽楠从幼苗、幼树到成年植株对光环境在外部形态、解剖结构和超微结构、生理特性方面的可塑性及动态响应规律，找出不同年龄阶段闽楠获得最佳光合生产力的光环境阈值。通过人工模拟不同光强光质的培养试验，测定光强、光质协同作用下闽楠的形态、生理及内源激素变化，进行耐荫相关基因的差异表达及Real-timePCR分析，探讨光强和光质是如何共同作用塑造闽楠的表型，影响其生理特性，进而导致光合生产力的分异；揭示闽楠在不同光环境下的激素应答及响应和适应的分子机理。在理论上为进一步的探讨光受体对遮荫信号的识别及如何调控下游基因的表达奠定基础；在实践上指导闽楠苗木培育、人工林营造各阶段的光环境调控，促进闽楠生长。

为解决闽楠人工林不同生长发育阶段的光环境调控问题，研究了闽楠耐荫性随年龄和光环境变化的动态响应规律、光质光强协同作用下闽楠的生理生化响应和激素应答以及光强光质协同作用下闽楠的转录组学。结果表明：闽楠植株随龄级和光环境表现出极高的表型可塑性。天然群落中闽楠植株的形态、生理可塑性与人工模拟不同光强环境下幼苗、幼树的表现是一致的。闽楠幼苗耐弱光能力强，弱光下闽楠的适应策略是增大叶面积、延长叶柄、降低栅/海和叶片厚度，增加单位面积基粒数、基粒片层数、内囊体厚度及叶绿体长/宽比，并合成更多的叶绿素来促进光能的吸收传递和转换；通过增加捕光组分和Rubisco的氮分配来提高弱光环境下的光合氮利用效率。随着龄级增加，闽楠对光照需求增加，闽楠植株的形态和生理可塑性倾向于适应强光环境。闽楠在不同生长阶段的光环境阈值分别为：苗期35%-50%; 幼树期60%～70%,高大植株80～100%。蓝光是对闽楠生长发育有利的光质，对其形态、生理和生长都有显著的促进作用。蓝光、绿光、红光比例不同，闽楠叶片对光强的响应不同，当光强为 235μmol·m-2·s-1，B:G:R=6:1有利于闽楠的生长发育及其各项生理活动的进行。闽楠幼苗叶片内源激素对不同光质和光强组合的响应不同，GA3和ABA是受蓝光、绿光、红光比值和光量子密度变化影响较大的激素。与叶绿素合成相关基因（GSA、PORA、PORB、CAO等）和其他结构基因的上调，是弱光下叶绿素 a 和叶绿素b含量增加的重要原因，这些基因在强光下的表现则相反。天然群落调查、人工模拟不同R:FR的实验和林冠下的造林试验均表明，R:FR比值是影响闽楠生长发育、生理特性的重要因子。随着荫蔽信号（R:FR）强度的增强，差异表达基因数量逐渐增加，三种荫蔽信号梯度处理共产生61个共有基因。61个共有基因主要富集在植物激素信号转导通路（EREBP，SAUR）、第二信使Ca2+结合蛋白钙调素（CML）、以及热激蛋白HSP20和HSFF上。随荫蔽信号增强， phyB 、LHCB3表达上调，LHCB基因先上升后下降，参与光合系统II的基因psbM、psbO、psbP大致趋势为先上升后下降。