不同天气类型下UV-B辐射对高山植物美丽风毛菊叶片PSⅡ光化学效率的影响分析

Effects of solar UV-B radiation on the efficiency of PSⅡ photochemistry in the alpine plant Saussurea superba under different weather conditions in the Qinghai-Tibet Plateau of China

以中国科学院海北高寒草甸试验站地区的美丽风毛菊(Saussurea superba)为材料,通过短期滤除自然光谱中紫外线B(UV-B)辐射成分的途径,研究了UV-B辐射对叶片光系统Ⅱ(PSⅡ)光化学效率的影响。不同天气的归纳分析表明,随可见光辐射的降低,暗适应3min的PSⅡ最大光化学量子效率(F(v)/F(m))显著升高;与此同时PSⅡ实际光化学量子效率(ΦPSⅡ)和光化学猝灭系数(qP)也显著升高,非光化学猝灭系数(NPQ)则显著降低。滤除UV-B辐射后,3种典型天气类型下的F(v)/F(m)均略有升高趋势;且ΦPSⅡ和qP增加,而NPQ略有降低趋势。量子效率的相对限制(L(PFD))和PSⅡ反应中心开放程度(qL)的进一步分析表明,UV-B辐射能显著影响辅酶A还原状态,对高山植物美丽风毛菊的光合机构具有负影响。综上可知,自然光中的可见光辐射是影响PSⅡ激发能捕获效率的重要因素,PSⅡ反应中心的光化学效率和非光化学能量耗散主要受光和有效辐射的影响;滤除UV-B成分能减缓PSⅡ反应中心的光抑制程度。

Aims Strong solar UV-B radiation accompanied with strong solar visible radiation is a characteristic of the en-vironment of China＇s Qinghai-Tibet Plateau.Previous study confirmed that current ambient UV-B intensity has a small negative influence on the physiological response of the photosynthetic apparatus of the alpine plant Saus-surea superba.Our objectives were to further analysis the influence of ambient UV-B intensity on PSⅡ photo-chemistry efficiency under different weather conditions.Methods Short-term field experiments of UV-B were conducted during the luxuriant growing season in Ko-bresia humilis meadow in the Haibei Alpine Meadow Ecosystem Research Station.We used the pulse-modulated in vivo chlorophyll fluorescence technique to obtain rapid information on the effects of UV-B intensities on pho-tosynthetic performances in the native alpine plant S.superba.The maximum quantum efficiency of PSⅡ photo-chemistry（F（v）/F（m）） was measured after 3 minutes of dark radiation.The PSⅡ photochemistry efficiency and non-photochemical quenching parameters were also measured.All chlorophyll fluorescence parameters were sta-tistically analyzed with SPSS 11.0 software according to sunny,cloudy and shady weather states.Two-way ANOVA and least significant difference method（LSD） were used to compare differences among UV-B treatments and weather states.Important findings There were significant increases of F（v）/F（m） in both ambient UV-B and low UV-B treatments when the weather changed from clear days to overcast days.Although there were no significant differences,F（v）/F（m） showed an increased trend in low UV-B when compared with ambient UV-B in all three weather states.This suggests that ambient UV-B intensity can delay the recovery of optimal photochemistry efficiency in S.su-perba.There were（a） increased tendency in actual photochemical efficiency of PSⅡ（ΦPSⅡ） and photochemical quenching（qP） and（b） small decreased tendency in non-photochemical quenching（NPQ） in low UV-B treatment in comparison with ambient UV-B;however,all those fluorescence parameters were significantly changed among the three weather states.The variation of these PSⅡ photochemistry efficiency parameters demonstrated that natural UV-B component can limit the photosynthetic performance.Further analysis confirmed that significant difference（p 0.05 on sunny days and p 0.01 on shady days） existed in relative limitation of quantum effi-ciency（L（PFD）） and fraction of opened PSⅡ centers（qL）.Although its effects were not always significant when compared with the influence of photosynthetically active radiation（PAR）,UV-B radiation can influence primary quinine electron acceptor of PSⅡ（QA） and there were negative effects on photosynthetic organization in S.su-perba.