遮荫处理对梅叶冬青叶片形态、光合特性和生长的影响

为了解遮荫环境对梅叶冬青(Ilex asprella)生长和光合特性的影响,采用遮荫网的方法模拟85%、56%和全光照等3种光照环境,研究了遮荫对其生长、光合参数以及生物量等的影响。结果表明,经一年遮荫处理后,梅叶冬青的叶绿素a、b和叶绿素总量都随着遮荫强度的增加而显著增高,胡萝卜素含量则显著降低。与对照相比,56%遮荫处理显著提高梅叶冬青的最大净光合速率和光饱和点,分别提高了17.6%和25.2%,但是85%遮阴处理则显著降低最大净光合速率和光饱和点,分别降低了18.2%和24.1%,两种遮荫处理均显著降低了光补偿点。叶长、叶宽、比叶面积、单片叶面积和叶片含水量均随着遮荫强度的增加而显著增加,而叶片厚度则显著减小。遮荫处理明显抑制整株生物量增长,减小根冠比,但是株高、冠幅和径向生长随遮荫处理时间不同而有所变异。因此,梅叶冬青有耐荫偏阳的特性,在林下种植时需及时调控乔冠层的透光率,一般应大于44%。

Effects of Shading on Leaf Morphology, Photosynthetic Characteristics, and Growth of Ilex asprella

In order to explore the adaptability of Ilex asprella under shading environment, the growth, photosynthetic parameters, and biomass of I. asprella were studied under three light environments, including 85% shading, 56% shading, and full sunlight. The results showed that the contents of chlorophyll a, b, and a+b of I. asprella leaves significantly increased with shading intensity increment, while the content of carotene decreased significantly after one year shading. Compared with control, 56% shading significantly increased the maximum net photosynthetic rate by 17.6% and light saturation point by 25.2%, whereas 85% shading decreased the maximum net photosynthetic rate by 18.2% and light saturation point by 24.1%. The light compensation points significantly decreased under both 85% and 56% shading. The length, width, area, and water content of leaves, specific leaf area increased significantly under shading, but the leaf thickness reduced. The individual biomass and root shoot ratio significantly decreased under shading, but the response of plant height, crown area, and radial growth varied with the shading duration. Therefore, Ilex asprella is shade-tolerant and heliophilous species, it is critical to adjust the light transmittance of the canopy layer when planting in understory layer. Generally, the light transmittance of canopy should be greater than 44%.