披针叶茴香对变化光环境的表型可塑性

植物对变化光环境的表型可塑性大小影响其在林下生境中分布、生长和更新。为探讨披针叶茴香在不同光环境下的整体表型可塑性及其适应机制,采用遮荫试验模拟5种光照条件(100%、52%、33%、15%和6%相对光照强度),研究了不同光环境下披针叶茴香叶片形态、生理、解剖结构、根系形态以及生物量分配等的变化。结果表明:叶生物量在5种光照处理之间差异不显著,但叶面积和比叶面积均随光照强度减弱显著增加。遮荫处理增加了叶绿素a、叶绿素b和类胡萝卜素的含量,但叶绿素a/b比值随光照强度减弱而降低。遮荫降低了非结构性碳水化合物(淀粉和可溶性糖)和可溶性蛋白的含量,增加了叶片氮和磷含量,对叶片氮/磷比影响较小。在52%和33%相对光照处理下,叶片中硝酸盐含量最低,而在100%和6%相对光照处理下硝酸盐积累较多。根生物量、细根和粗根的长度、表面积以及比根长和比根表面积在5种光照处理之间均没有显著差异,根系氮含量在低光环境(15%和6%相对光照处理)中显著降低。随光照强度减弱,披针叶茴香采取保守生存策略,并没有增加叶生物量的分配,而是分配较多的生物量给枝条和树干,储存能量。综合来看,披针叶茴香具有较宽的光生态幅,在6%—100%光照强度下均能正常生长,遮荫有利于披针叶茴香地上和总生物量的积累,52%的相对光照条件下生长最佳。变化光环境下根系性状和整体结构的可塑性相对较低,叶片生理性状的可塑性在披针叶茴香适应光环境变化过程中发挥了主要作用。

Phenotypic plasticity of Illicium lanceolatum in response to varied light environments

The phenotypic plasticity of plants in varied light environments affects their distribution, growth, and regeneration in the understory environment. To investigate the phenotypic plasticity and adaptation mechanisms of Illicium lanceolatum in different light conditions, five light conditions (100%, 52%, 33%, 15%, and 6% relative light intensity) were simulated in the shading experiment. The changes in leaf morphology, physiology, anatomical structure, root morphology, and biomass allocation of I. lanceolatum in different light conditions were studied. The results showed that there was no significant difference in leaf biomass between the five light treatments, and the leaf area and specific leaf area increased significantly with the decrease of light intensity. The shading treatments enhanced the contents of chlorophyll a, chlorophyll b, and carotenoid. However, the chlorophyll a/b ratio decreased with the decrease of light intensity. Shading reduced the contents of non-structural carbohydrates (starch and soluble sugar) and soluble protein, and increased the leaves'' nitrogen and phosphorus contents, but the nitrogen/phosphorus ratio of leaves was less affected by light gradients. The nitrate content of the leaves in 52% and 33% relative light treatments was the lowest, whereas the nitrate content was higher in the 100% and 6% relative light treatments. Root biomass, fine root and root length, root surface area, specific root length, and specific root surface area were not significantly different among the five light treatments. The content of root nitrogen was significantly reduced in the low light environments (15% and 6% relative light intensities). As light intensity decreased, I. lanceolatum adopted a conservative survival strategy, which did not invest in leaf biomass, but allocated more biomass to the branches and trunks to store energy. As a whole, I. lanceolatum had a wide light ecological amplitude and could grow normally in 6%-100% light intensities. Shading was beneficial for the accumulation of aboveground biomass and total biomass for I. lanceolatum, and the optimal growth condition was 52% relative light intensity. The plasticity of the root traits and whole structure was relatively lower in the different light environments, and the plasticity of the leaf physiological traits played a key role for I. lanceolatum to adapt to varied light environments.