Krause G Heinrich, Grube Esther, Koroleva Olga Y, Barth Carina, Winter Klaus
Smithsonian Tropical Research Institute, Apartado 2072, Balboa, Ancon, Panama.
Institute of Plant Biochemistry, Heinrich Heine University Düsseldorf, Universitätsstr. 1, 40225 Düsseldorf, Germany.
Funct Plant Biol. 2004 Aug;31(7):743-756. doi: 10.1071/FP03239.
Seedlings of neotropical forest trees grown in low light were exposed to 0.5-9 h d direct sunlight, for up to 3 months, to test the capability of mature shade leaves to acclimate to full solar visible and UV radiation. Photosynthetic pigments and the antioxidant, ascorbate, were analysed in leaves of two pioneer and two late-succession species. Seedlings of one or two of these species were used to assess further acclimative responses. Sun-exposure for 0.5 or 1 h d resulted in strongly decreased α-carotene and increased β-carotene and lutein levels. The pool size of xanthophyll-cycle pigments (sum of viola-, anthera- and zeaxanthin) was increased and their turnover was enhanced. These changes were associated with an increase in the capacity of non-photochemical fluorescence quenching and its 'energy-dependent' component, qE, and with reduced susceptibility to photoinhibition of PSII. Prolonged exposure to full direct sunlight (approximately 4 or 9 h d) resulted in a marked decrease of chlorophyll a + b content and increase in chlorophyll a / b ratios and the pool of xanthophyll-cycle pigments (based on chlorophyll), leading to extremely high zeaxanthin levels during high-light periods. Contents of ascorbate and UV-B-absorbing substances were substantially increased. PSI activity exhibited a response to full sunlight that is characteristic of sun leaves. Rates of net photosynthetic CO assimilation under saturating light were increased. The data show that mature shade leaves of seedlings of both early- and late-succession tree species can substantially acclimate to full-sunlight conditions by employing similar physiological mechanisms.
将新热带森林树木的幼苗种植在弱光环境中，使其接受每天0.5 - 9小时的直射阳光照射，持续长达3个月，以测试成熟的阴生叶片适应全日照可见光和紫外线辐射的能力。对两个先锋树种和两个演替后期树种的叶片进行了光合色素和抗氧化剂抗坏血酸的分析。使用其中一两种树种的幼苗来评估进一步的适应性反应。每天接受0.5或1小时的阳光照射会导致α - 胡萝卜素含量大幅下降，β - 胡萝卜素和叶黄素含量增加。叶黄素循环色素（紫黄质、花药黄质和玉米黄质的总和）的库大小增加，其周转加快。这些变化与非光化学荧光猝灭能力及其“能量依赖”成分qE的增加相关，并且对PSII光抑制的敏感性降低。长时间暴露在全日照直射阳光下（约每天4或9小时）会导致叶绿素a + b含量显著下降，叶绿素a / b比值和叶黄素循环色素库（基于叶绿素）增加，导致高光期玉米黄质水平极高。抗坏血酸和紫外线B吸收物质的含量大幅增加。PSI活性表现出对全日照的反应，这是阳生叶的特征。饱和光照下净光合CO同化速率增加。数据表明，早期和后期演替树种幼苗的成熟阴生叶片都可以通过采用相似的生理机制来大幅适应全日照条件。
