热带雨林不同生态习性树种幼苗光合作用和抗氧化酶对生长光环境的反应

Response of photosynthesis and antioxygenic enzymes in seedlings of three tropical forest tree species to different light environments.

于雨季研究了西双版纳热带雨林后期演替树种思茅木姜子 (Litseapierreivar .szemaois)、五桠果叶木姜子 (L dilleniifolia)和先锋树种毛果桐 (Mallotusbarbatus)幼苗的光合、荧光特征和抗氧化酶等对 3种光水平 (5 0 %、2 5 %和 8% )的适应特性 .结果表明 ,毛果桐的最大光合速率 (Pmax)随光水平升高呈增加趋势 ,而两种木姜子则在 5 0 %光水平下Pmax最小 .Fv/Fm 的日变化表明 ,3个种在 2 5 %和 5 0 %光水平下发生可逆光抑制 ,两种木姜子较重 .5 0 %光水平下 ,五桠果叶木姜子受到长期光抑制 .思茅木姜子和毛果桐的丙二醛 (MDA)和H2 O2 含量 ,以及超氧化物歧化酶 (SOD)、过氧化氢酶 (CAT)、抗坏血酸过氧化物酶(APX)活性随光水平升高而增加 ,表明光水平升高 ,致使植物受光胁迫的影响加剧 ,增强抗氧化酶系统则减轻了其伤害 .

This paper studied the response of photosynthesis,chlorophyll a fluorescence and 3 antioxygenic enzyme activities in the seedlings of a pioneer species (Mallotus barbatus) and two endangered sub-canopy tree species (Litsea pierrei var.szemaois and L.dilleniifolia) in Xishuangbanna tropical rain forest to different light environments.Three light regimes (50%,25% and 8% full sunlight) were designed for the seedlings.The largest values of maximum photosynthetic rates (P max) of L.pierrei var.szemaois and L.dilleniifolia were documented at 25% and 8% sunlight,respectively,which showed that the two sub-canopy species had poor ability in photosynthetic acclimation to high light.In contrast,the P max of M.barbatus increased with light level.During a day,the maximum photochemical efficiency (F v/F m) of the photosystem Ⅱ in all the three species grown under three light levels showed minimum values at noon,and the lowest F v/F m values were shown in seedlings at 50% sunlight.Under 50% sunlight,the F v/F m values at dawn were lower in L.dilleniifolia than in the same species under other two light levels,indicating that sustained photoinhibition occurred in this case.The contents of malondialdehyde (MDA),H 2O 2,and activities of ascorbate peroxidase (APX),superoxide dismutase (SOD),catalase (CAT) of both L.pierrei var.szemaois and M.barbatus increased with stronger irradiance,which revealed that these two species were able to alleviate photodamage under high light stress by increasing their antioxigenic activities.But,high content of MDA revealed that L.dilleniifolia was probably suffered from membrane damage.In conclusion,our data revealed that the pioneer species M.barbatus had a high capacity to acclimate to different light environments,particularly high light,while the two subcanopy Litsea species had poor ability in acclimation to high light.Based on the findings of the present study,we suggest that the small populations and endangered status of both L.pierrei var.szemaois and L.dilleniifolia in natural environment could be partially due to their poor flexibility in response to changed light environment resulted from habitat fragmentation.