挺水植物与浮叶植物光合荧光特性的差异

摘要

为探讨自然生境中不同生活型水生植物光合生理特征的差异,选取4种挺水植物菖蒲(Acorus calamus L.)、再力花(Thalia dealbata Fraser)、梭鱼草(Pontederia cordata L.)、茭草(Zizania latifolia(Griseb.) Stapf),以及4种浮叶植物黄睡莲(Nymphaea mexicana Zucc.)、莼菜(Brasenia schreberi J.F.Gmel.)、金银莲花(Nymphoides indica(L.)O.Kuntze)、菱(Trapa bispinosa Roxb.)为研究对象,比较其叶绿素荧光参数、色素组成和比叶重的差异.研究发现,高光强下挺水植物电子传递速率(ETR)、非光化学淬灭(NPQ)等光合荧光参数、以及低光强下ETR拟合曲线的初始斜率(α)均值显著大于浮叶植物.不同挺水植物间光系统Ⅱ(PSⅡ)最大光化学效率(Fv/Fm)、ETR、NPQ、最大潜在电子传递速率(Ps)、最大电子传递速率(ETRm)及饱和光强(Em)变化幅度较大;不同浮叶植物间上述参数变化幅度较小.挺水植物叶绿素(Chls)、类胡萝卜素(Cars)含量均值也高于浮叶植物.但由于比叶重(SLW)的影响,不同水生植物间单位叶面积和单位叶鲜重色素含量的变化规律略有不同.挺水植物中再力花、梭鱼草光合能力较强,其光合荧光参数和色素比例均符合典型阳生型特征;菖蒲、茭草光合能力略弱,部分指标符合阴生型特征.4种浮叶植物各指标均符合阳生型特征.实验推测,挺水植物和浮叶植物由于叶片所处环境不同,其光合适应机制存在明显分化.挺水植物叶片所处环境异质性较大,因而不同物种之间光合参数适应范围也大;浮叶植物叶片所处环境相对均一,因而光合参数差异也小.浮叶植物也不依赖NPQ进行高光保护.在湿地植被恢复工具种筛选过程中应综合考虑环境异质性和不同物种光适应能力的差异.%Emergent and floating-leaved macrophytes,two different life forms of primary producers in shallow lakes and riparian zones,play important roles in nutrient cycling and energy flow of aquatic ecosystems.To investigate the differences in photosynthetic characteristics between the two forms of macrophytes,chlorophyll fluorescence,pigment composition,and special leaf weight (SLW) of four emergent macrophytes (Acorus calamus L.,Pontederia cordata L.,Thalia dealbata Fraser,Zizania latifolia (Griseb.) Stapf) and four floating-leaved macrophytes (Nymphaea mexicana Zucc.,Brasenia schreberi J.F.Gmel.,Nymphoides indica (L.) O.Kuntze,Trapa bispinosa Roxb.) growing in natural habitats were compared.In general,emergent macrophytes showed higher electron transport rate (ETR) and non-photochemical quenching (NPQ) under high irradiation,as well as relatively higher initial slope (α) of ETR curve under low light,than did floating-leaved plants.Broader ranges on maximum quantum yield of PS Ⅱ (Fv/Fm),ETR,NPQ,maximum potential ETR (Ps),maximum ETR (ETRm) and saturating irradiance (Em) were also found among different species of emergent macrophytes.Average chlorophyll (Chls) and carotenoid (Cars) contents were also higher in emergent macrophytes than in floating-leaved ones.However,due to the discrepancy of SLW,the trends of pigment amount among species on a fresh matter basis differed from those per leaf area unit.Among the four emergent macrophytes,T.dealbata and P.cordata exhibited relatively higher photosynthetic ability,and all fluorescence parameters together with pigment ratios (Chl a/b,Chls/Cars) indicated they belonged to the sun type.However,A.calamus and Z.latifolia exhibited relatively lower photosynthetic ability,and part of the parameters were closer to the shade type.All four floating-leaved species exhibited as sun type.This suggests that the heterogeneity of environments contributes to the discrepancy of leaf photosynthetic abilities.Emergent leaves grow in highly diverse environments,so their photosynthetic parameters have broad ranges,whereas the environments for floating leaves are relatively stable,so their parameters are limited to small ranges.It may not be necessary for floating-leaved macrophytes to develop NPQ and internal heat dissipation to prevent high irradiation damage.In conclusion,special attention should be paid to both environmental heterogeneity and discrepancy of adaptation abilities when selecting aquatic macrophytes for wetland restoration.