毛白杜鹃‘紫萼’(Rhododendron mucronatum var.plenum)的光合“午休”与园林造景的研究

MIDDAY DEPRESSION OF PHOTOSYNTHESIS OF AZALEA (RHODODENERON MUCRONATUM VAR,PLENUM) AND APPLICATION FOR LANDSCAPE DESIGN

本试验探明:杜鹃在春末晴天就产生光合“午休”现象。设置了3个处理分别测定净光合速率日进程,基本上肯定了强光抑制(>1100μE/m.s)是导致杜鹃“午休”的主要原因,通过以杜鹃为下层的园林人工群落中光与开花指数的关系研究证明了杜鹃光生态特性。最后,以此为依据提出了杜鹃在园林中配植的理想位置。

The photosynthesis of azalea exhibited a midday depression on bright sunny days in the end of spring under field conditions. The Pn increased rapidly in a few hours after sunrise, reached the first peak at about 10:30 A.M., followed by a marked decease untill about 2:10 P.M., then increased again and reached the second lower peak at about 3-00P. M. Shading the leaves by the shadow of willow tree or by the cover of gauze with 50-34% of Light intensity of natural light, no midday depression was found. The pattern of stomatal conductance or transpiration between sunny and shading leaves showed only slight difference.This implies that the main cause of the midday depression of photosynthesis could be considered the high solar irradiation (above H00μE/M2.S). Further, studying of flowering index related to RLi also supported this conculsion.Based on the experiment, it is suggested that azalea should be located in the eastside of hill, south-east of forest or trees, where strong solar irradiation could be shaded from noon to afternoon, in landscape design.