光合电子流对光响应的机理模型及其应用

光合电子流对光响应的机理可以揭示植物光合电子流与光强、植物捕光色素分子物理特性之间的关系。该文讨论了光合电子流对光响应的机理模型的特性以及捕光色素分子的物理性质, 并利用此模型拟合了山莴苣(Lagedium sibiricum)、一年蓬(Erigeron annuus)和紫菀(Aster tataricus)的光合电子流对光响应的曲线。由此模型不仅可以得到植物的最大光合电子流、饱和光强、初始斜率等参数, 还可以获得捕光色素分子有效光能吸收截面和处于最低激发态的捕光色素分子数对光的响应关系。结果表明: 随光强的增加, 山莴苣的捕光色素分子的有效光能吸收截面下降最快, 紫苑的下降速度最慢; 山莴苣处于最低激发态的捕光色素分子数增长速度最快, 紫苑的增长速度最小。捕光色素分子的有效光能吸收截面随光强增加而下降、处于最低激发态的捕光色素分子数随光强增加而增加的特性将减少其光能的吸收和激子的传递, 因而有利于减少强光对植物产生的光伤害。

A mechanistic model of light-response of photosynthetic electron flow and its application

Aims Our objectives were to introduce a mechanistic model of light-response of photosynthetic electron flow and to understand how the photosynthetic electron flow respond to light intensity and the characteristics of light-harvesting pigment molecules.Methods Light-responses of photosynthetic electron flow were measured in Lagedium sibiricum, Erigeron annuus and Aster tataricus by using a LI-6400-40B, and the curves were fitted by a mechanistic model of light-response of photosynthetic electron flow. Important findings (1) The mechanistic model of light-response of photosynthetic electron flow not only well described the light-response curves of photosynthetic electron flow in L. sibiricum, E. annuus and A. tataricus, but also obtained some key photosynthetic parameters, e.g. maximum photosynthetic electron flow, saturation irradiance and initial slope of the light-response curve; the fitted photosynthetic parameters were similar to the measured values. (2) The effective light absorption cross-section of light-harvesting pigment molecules quickly decreased with increasing irradiance in L. sibiricum, and showed slowest rate of decrease in E. annuus. (3) The light-harvesting pigment molecules in the lowest excited state increased most rapidly with increasing irradiance in L. sibiricum, and most slowly in E. annuus. In conclusion, compelling evidence indicates that decrease in effective absorption cross-section and increase in the number of light-harvesting pigments in the lowest excited state would reduce light energy absorption.