天目山自然保护区典型阔叶林的光合特性

摘要

To understand the internal mechanism of photosynthesis ability, adaptability and stress resistance of typical broad-leaved species in Tianmushan National Nature Reserve, photosynthesis light response, chlorophyll fluorescence and relative chlorophyll content were measured in autumn and winter. Broad-leaved species studied included Daphniphyllum macropodum, Cyclobalanopsis myrsinaefolia and Hydrangea chinensis Maxim. Results showed that light saturation point ( LSP) , maximum net photosynthetic rate ( Amax) , apparent quantum efficiency ( AQY) , actual photochemical efficiency ( Fv′/Fm′) , actual quantum yield ( Yield) and ap-parent electron transport rate ( ETR) all decreased and then increased in autumn and winter. All these parameters were higher in D. macropodum than the other two species. Light compensation point ( LCP) was highest in D. macropodum and lowest in H. chinensis in autumn.Dark respiration rate (Rd) was overally low in D. macropodum, with that of C. myrsinaefolia being the peak in autumn while that of H. chinensis being the peak in winter. Photochemical quenching coefficient ( qP) and non photochemical quenching co-efficient ( NPQ) shared a similar pattern, which qP and NPQ were highest in H. chinensis, and followed by C. myrsinaefolia and then D. macropodum in autumn, while in winter they were higher in Cyclobalanopsis myrsinaefolia than D. macropodum. With regard to stress resistance, three species demonstrated different mechanisms, in which D. macropodum slowed down photosynthesis rate and dark respiration rate while C. myrsinaefolia and H. chinensis transfered excessive light into heat. Relative chlorophyll content was sig-nificantly lower in autumn than winter for both D. macropodum and C. myrsinaefolia. At the same point, relative chlorophyll content was highest in D. macropodum and lowest in H. chinensis, with C. myrsinaefolia being the intermediate. Correspondingly, average net photosynthesis ( Pn) was higher in D. macropodum than C. myrsinaefolia in both seasons, and in autumn average Pn of H. chinensis was between the other two species, matching the pattern of chlorophyll relative content and temperature and humidity change, which started with a decline and followed by a rise.%对天目山自然保护区内典型阔叶林树种交让木( Daphniphyllum macropodum )、小叶青冈( Cyclobalanopsis myrsinaefo-lia)、中国绣球( Hydrangea chinensis Maxim)，在秋冬季节的光合作用光响应、叶绿素荧光以及相对叶绿素含量进行了测定分析。结果表明，(1)2个季节中，光饱和点(LSP)、最大净光合速率(Amax)、表观量子效率(AQY)、实际光化学效率(Fv′/Fm′)、实际量子产量( Yield)、表观电子传递速率( ETR)均是先减小后增大，均以交让木最高。光补偿点( LCP)秋季以交让木最高，小叶青冈次之，中国绣球最低；冬季交让木高于小叶青冈；暗呼吸速率( Rd)总体上交让木最低，秋季中国绣球最高，冬季小叶青冈较高。光化学猝灭系数( qP)秋季中国绣球最高，其次是小叶青冈，交让木最低；冬季小叶青冈高于交让木。非光化学猝灭系数( NPQ)的变化趋势与qP相同。胁迫的相应机制：交让木为关闭一部分光合系统，降低暗呼吸速率；小叶青冈和中国绣球主要是将过剩的光能耗散为热能。(2)交让木和小叶青冈的相对叶绿素含量均表现为秋季小叶青冈>中国绣球，差异极显著。净光合速率( Pn)表现为交让木>小叶青冈；秋季中国绣球Pn位于二者之间。这与相对叶绿素含量的变化趋势基本一致，都是随着温湿度的变化呈先下降后上升的变化规律，但均为正值。