广西青梅幼苗与成年树木光合特性和叶片显微结构的比较研究

Comparative study on photosynthetic characteristics and leaf microstructure of Vatica guangxiensis seedling and adult plants

关键词:  广西青梅，拟合模型，光合特性，叶片显微结构，叶绿素

Key words:  Vatica guangxiensis, fitting model, photosynthetic characteristics, leaf microstructure, chlorophyll

摘要:

广西青梅为国家一级保护野生植物和极小种群野生植物。该文利用Li-6400便携式光合测定系统分析仪和真空电子扫描镜对广西青梅幼苗和成年树木光合生理特性与结构特征进行比较分析，探究其不同生长发育阶段叶片的光合能力和叶片结构之间的差异。研究表明：（1）直角双曲线修正模型是广西青梅光响应拟合的最佳模型。（2）成年树木叶片的最大净光合速率（Pnmax）、光饱和点（LSP）和暗呼吸速率（Rd）均显著高于幼苗而光补偿点（LCP）低于幼苗（P<0.05）。（3）幼苗的叶绿素a、叶绿素b、叶绿素（a+b）和类胡萝卜素均显著低于成年树木（P<0.05）。（4）成年树木叶片的气孔器长轴、气孔器面积和气孔密度显著高于幼苗；成年树木叶片的叶面积和比叶重（SLW）显著（P<0.05）大于幼苗，而比叶面积（SLA）小于幼苗。综上所述，广西青梅具有幼苗喜阴而成年树木喜阳的光合特性。幼苗的光适应能力，光能利用率较弱以及成年树木过度遮阴导致幼苗无法进行充分光合以满足生长需求，是幼苗无法成长为大树的重要原因。在广西就地保护中可通过人为的方式，对乔木层林木进行人工“开窗”，提供相对充足的光源，以利于广西青梅大苗的生长发育成大树和种群的更新；而在引种栽培中，广西青梅幼苗时期需要适当的遮阴处理，以及移栽至有一定荫蔽度的环境中。

Abstract:

Vatica guangxiensis is a national first-class protected wild plant and extremely small populations wild plant. This paper provides a comparative analysis of the photosynthetic physiological characteristics and structural features of Vatica guangxiensis seedlings and adult trees. The Li-6400 portable photosynthesis measurement system analyzer and vacuum electron scanning microscope were utilized to investigate the differences between the photosynthetic capacity and leaf structure of leaves at different stages of growth and development. The results were as follows: (1) The right-angled hyperbolic modified model was the best model to fit the light response of Vatica guangxiensis seedlings and adult plants. (2) The maximum net photosynthetic rate(Pnmax), light saturation point (LSP) and dark respiration rate (Rd) of adult leaves were significantly higher than those of seedlings, the light compensation point (LCP) of adult plants was lower than that of seedlings(P<0.05). (3) Chlorophyll a, chlorophyll b, chlorophyll (a+b) and carotenoids in seedlings were significantly lower than in adult plants(P<0.05). (3) The stomatal long axis, stomatal organ area and stomatal density of adult plants were significantly higher than those of seedlings; the leaf area and specific leaf weight (SLW) of adult plants were significantly larger than seedling (P<0.05), and the specific leaf area (SLA) was smaller than seedling. In summary, Vatica guangxiensis exhibits photosynthetic characteristics of a shade-loving seedling and a sun-loving adult tree. The seedlings have weak light adaptation ability and light energy utilization, and are unable to photosynthesize sufficiently to meet their growth needs due to excessive shading by adult trees. This is a significant reason why seedlings are unable to grow into large trees. Therefore, for insitu conservation of Vatica guangxiensis, human interference can be used to artificially create ‘windows’ in the tree layer to provide sufficient light sources. This is conducive to the growth of Vatica guangxiensis seedlings into large trees and the renewal of the population. On the other hand, for the introductory cultivation of Vatica guangxiensis, the seedlings need to be appropriately shaded and transplanted to a certain degree of shade. During the initial cultivation process, it is important to provide appropriate shading for seedlings and transplant them to an environment with a suitable level of shade.