两种五倍子蚜虫冬寄主藓类植物的光合特性及其与光照、温度和植物体水分含量变化的关系

使用CI-301PS(CID Inc.USA)对生长于冬季和春季的大羽藓(Thuidium cymbifolium)与垂藓(Chrysocladium retrorsum)的净光合速率(Pn)及其与光照、温度和植物体水分含量的关系进行了研究.结果表明,大羽藓和垂藓的光合能力分别达到141和117μmolCO₂kg^-1·dw·s^-1,光合能力从冬季到春季呈上升趋势.这两种藓类植物的光响应曲线比较相似,光饱和点高达800～900μmol·m^-2s^-1,光补偿点为40～50μmol·m^-2s^-1,光合作用最适温度在春季为25～36℃,而冬季为20～30℃.同时对于低温又具有很强的抗性,在冰点以下的温度条件下(-15～0℃)能够保持一定的净光合.净光合速率的水分响应曲线表明,这两种藓类的最适水分含量为200～300(400)%dw,水分含量降低到150%dw时光合作用开始受到抑制,在40%～50%dw时净光合降低到零或略变为负数.结果表明,大羽藓和垂藓都属于耐干旱、强阳性的藓类,但垂藓在这几个方面略逊于大羽藓.

Net photosynthetic rate of two species of wintering host mosses for gullaphids and its response to light, temperature and water content

The net photosynthesis of Thuidium cymbifolium and Chrysocladium retrorsum, two species of wintering host mosses for gullaphids,and its response to light,temperature and water content were measured with CI 301PS(CID Inc.USA)both in winter and spring.The photosynthetic capacity of Thuidium cymbifolium and Chrysocladium retrorsum was about 141 and 117μmolCO₂kg^-1 dw·s^-1,respectively,and trended to increase from winter to spring.The light saturation point of these two mosses at 800～900μmol·m^-2·s^-1 was much higher than that of many other mosses,and the compensation point ranged from 40 to 50μmol·m^-2·s^-1.The temperature response curves of these two mosses were similar,with optium temperature ranging from²5 tO₃6℃ in spring,and from²0 tO₃0℃ in winter.When the temperature was below the freezing point(-15 to 0℃),they both maintained a distinct net photosynthesis,with the optimum water content ranging from²00 tO₃00(400)%dw.The photosynthesis started to be restrained evidently,when the water content declined to about 150%dw.The gas exchange ceased or became negative,when the water content was as low as 40～50%dw.It can be inferred that these two species might be both poikilothermal and poikilohydric organisms,but the resistibility of T.cymbifolium to intense light and high temperature was higher than that of C.retrorsum.