不同光照梯度的遮荫处理对绒毛番龙眼幼苗生长的影响

在不同光照梯度,即100%自然全光照(natural sunlight,NS)、37.3%NS、15.5%NS、4.2%NS、1.6%NS和0.6%NS的人工遮荫条件下,研究了西双版纳季节雨林冠层树种绒毛番龙眼(Pometia tomentosa)幼苗的早期生长和定居后的生长特点。结果表明,光照是影响幼苗生长的重要环境因子。生长早期的幼苗基径和复叶数随遮荫程度的增加而降低;主根长、根冠比、总干重和单株叶面积均以37.3%NS处理最大;比叶面积随遮荫程度的增加而增大,而相对生长率则降低;幼苗株高在0.6%NS下增长最快,表明种子中贮藏的营养物质对幼苗的早期生长可能具有重要作用。37.3%NS处理对定居后绒毛番龙眼幼苗的生长最有利,幼苗的株高、基径、复叶数、叶轴长、复叶最多小叶数、单株叶面积、相对生长率和净同化率均在37.3%NS处理下获得最大增长;幼苗总干重随光照强度的减弱而降低;比叶面积在15.5%NS处理时最大。幼苗比叶面积和根冠比在生长过程中的波动可能是光照和土壤水分共同作用的结果。

Effects of Shading Treatments on the Growth of Pometia tomentosa Seedling

Pometia tomentosa is a dominant uppermost canopy tree species of vallyland forest in Xishuangbanna tropical seasonal rainforest,China. Under different light intensities such as 100% natural sunlight (NS), 37.3% NS, 15.5%NS, 4.2% NS, 1.6% NS, 0.6% NS in shade house, growth characteristics were studied in early development stage and established seedlings. Light was an important environmental factor for the growth of P. tomentosa seedlings. During the early growth stage of seedlings, basal stem diameter and paripinnate number were decreased with the increasing of shade, taproot length, root : shoot ratio, total dry weight and leaf area per seedling were maximal under 37.3% NS, specific leaf area (SLA) was increased with the increasing of shade, but the relative growth rate was declined. Seedlings grew fastest under 0.6% NS, suggesting that nutrients stored in seeds played an important role at the early growth stage. The treatment of 37.3% NS was best for established seedlings in seedling height, basal stem diameter, paripinnate number, rachis length, the maximum sub-leaflet number of individual paripinnate, leaf area per seedling, relative growth rate and net assimilation rate. Light intensity was positively correlated to total dry weight, and negatively to specific leaf area. The maximum of SLA was observed under 15.5% NS. The fluctuations of SLA and root : shoot ratio in developmental established seedlings may be responsible for light intensity and soil moisture.