喜树(Camptotheca acuminate)幼苗形态和光合作用对不同光环境的适应

Morphological and Photosynthetic Acclimation to Different Canopy Conditions in Seedling of Camptotheca acuminate

选择旷地、林隙、林下3种光环境,研究了喜树幼苗总生物量、生物量分配、株高、基茎、叶面积和光合作用的差异．结果表明:①旷地中幼苗的平均相对生长速率最大,总生物量累积最大,地下部分生物量分配明显增多; 林隙中叶生物量比显著增加;林下茎生物量比显著增加．②在林下和林隙环境中,喜树幼苗增加高度以截获更多的光能．比叶面积在林隙、林下显著高于旷地．③3种光环境中,净光合速率日变化均呈单峰型,约在中午12:00 时达到峰值,旷地中日均净光合速率大于林隙、林下．④林隙和林下光补偿点(LCP)降低适应低光环境,光饱和点 (LSP)在各环境中差异不大．喜树幼苗能通过不同的形态和生理特性的变化适应各光环境．

Camptotheca acuminate Decaisne （nyssaceae） is a native Chinese tree. The effect of shading on the biomass, the biomass allocation, plant height, stem diameter, leaf area and photosynthesis, and the seedling of C. acuminate grown under open field, forest gap, and forest understory were investigated. The result showed that Camptotheca acuminate had the highest RGR and biomass in open field. The biomass allocation strategy differed in the three environments： RMR increased in open field, LMR increased in forest gap and SMR increased in forest understory. In forest gap and forest understory, Camptotheca acuminate grew taller to intercept more light energy. The order of SLA from the highest to the lowest is forest gap, forest understory, and open field, the diurnal variations of net photosynthesis rates（Pn） are all ＂single-peaked＂ in the three environments, with maximumn values at 12：00. The order of the daily average Pn from the highest to the lowest is open field, forest gap, and forest understory. Camptotheca acuminate had the hightest light compensation point（LCP） in open field. LSP had no significant difference in the three en- vironments. Pmax was about 10 μmol· m^-2·s^-1 under open field and forest gap. seedlings of Camptotheca acuminate could acclimate to different canopy conditions through changes of physiological and morphological traits.