Xiao Wenfa

Growth and physiological responses of Distylium chinense seedlings to autumn and winter flooding

为阐明三峡库区岸生植物中华蚊母树(Distylium chinense)幼苗对水淹的耐淹机理, 通过设置对照组(CK)、半淹组(PF)、全淹组(CF)3个水淹处理, 模拟库区消落带秋、冬季淹水情况, 研究中华蚊母树幼苗在不同水淹时间和深度下的生长及生理生化特性.结果表明, 淹水显著影响中华蚊母树幼苗的生物量, 水淹150 d后, PF组植株和CF组植株根、茎、叶生物量均呈显著降低趋势, 同时受水淹影响, 植株根冠比也显著降低; 中华蚊母树幼苗在水淹前90 d 2组水淹处理植株叶片丙二醛(MDA)含量均与CK组植株差异不显著, 水淹120 d后, 中华蚊母树幼苗叶片MDA含量显著增加, 且随着水淹深度的增加而逐渐升高; 可溶性蛋白在各水淹处理中的变化有所差异, 水淹前60 d, 淹水并没有影响CF组植株可溶性蛋白含量, 但从水淹90 d开始, CF组植株可溶性蛋白含量有所上升, 而PF组植株可溶性蛋白含量在整个淹水期间均与CK组植株差异不显著; 2组水淹处理植株脯氨酸在水淹前期均显著上升, 但自水淹90 d后逐渐下降至CK组水平; 与MDA对水淹的响应一致, 水淹前期PF组和CF组植株抗氧化酶活性(超氧化物歧化酶、过氧化氢酶和抗坏血酸过氧化物酶)均没有出现明显影响, 但水淹后期2组水淹处理植株抗氧化酶活性均显著升高; 可溶性糖含量在不同水淹处理下有所差异, PF组植株叶片可溶性糖含量在整个淹水期间均与CK组植株差异不显著; 而CF组植株叶片可溶性糖含量随着水淹时间的延长逐渐降低.研究证明, 中华蚊母树幼苗生长及生理特性对秋、冬季水淹环境具有一定的调节能力, 是中华蚊母树幼苗能够在库区消落带存活生长的一个重要原因.

Response of gas exchange to neighborhood interference in leaves of teak (Tectona grandis L. f.) in a tropical plantation forest

Abstract The growth performance of individual plants in a population can be affected by the plant-plant interaction, which has been well recognized and is called neighborhood interference. Though mechanisms are still unclear, the variations in gas exchange parameters in relation to the neighborhood interference between individual plants are crucial for evaluating the effects of plant-plant interaction. CO 2 assimilation in leaves of teak under natural conditions of dry seasons and wet seasons as well as its response to variations in light flux density and CO 2 concentration in different neighborhood interferences were simultaneously measured with Li-6400 portable photosynthesis system in a 21-year-old tropical plantation forest in Jianfengling, Hainan Island, China. This article dealt with the change rule of neighborhood interference on tree characteristics of gas exchange and its dynamic response to light en-vironments of individual plants. Diurnal courses of photosynthesis of individual leaves were not affected by neighborhood interfer-ence, but net photosynthetic rates showed a negative relationship with the intensity of neighborhood interference. The ratio of daily average P n in weak, moderate, strong and heavy neighborhood interferences was 2.5:2.3:1.7:1.0, and the daily maximum P n in weak interference was 2.8 times that in heavy interference. Leaf transpiration and stomatal conductance decreased with the increasing of interference intensity. Characteristics of photosynthetic light response and CO 2 response changed with the neighborhood interference, and values of leaf gas exchange parameters including A sat , Q sat , α A , CE , V cmax and J max in weak interference were enhanced by 2.7, 1.3, 1.4, 2.7, 1.9 and 2.8 times, respectively, than those in heavy interference. But changes in those parameters partly depended on light environment and CO 2 concentration, and the influence of changes in light environment on weak interference individuals was sig-nificantly stronger than that on heavy interference. Beyond the growth CO 2 concentration, the influence resulting from changes in CO 2 concentration on heavy interference individuals was obviously stronger than that on weak interference. Neighborhood interference can be described as a major means of intraspecific competition of population in a plantation forest with uniform forest structure and consistent management. Carbon assimilation can be affected by the neighborhood interference, and result in divergence in growth performance. Indices of neighborhood interference can be used to evaluate the intraspecific competition, and based on this point, we can make maximum use of resources after stand structure has been well adjusted.