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Do mature shade leaves of tropical tree seedlings acclimate to high sunlight and UV radiation?

Do mature shade leaves of tropical tree seedlings acclimate to high sunlight and UV radiation? Seedlings of neotropical forest trees grown in low light were exposed to 0.5–9 h d –1 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 –1 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 –1 ) 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 2 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. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Functional Plant Biology CSIRO Publishing

Do mature shade leaves of tropical tree seedlings acclimate to high sunlight and UV radiation?

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Publisher
CSIRO Publishing
Copyright
CSIRO
ISSN
1445-4408
eISSN
1445-4416
DOI
10.1071/FP03239
Publisher site
See Article on Publisher Site

Abstract

Seedlings of neotropical forest trees grown in low light were exposed to 0.5–9 h d –1 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 –1 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 –1 ) 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 2 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.

Journal

Functional Plant BiologyCSIRO Publishing

Published: Jul 22, 2004

Keywords: Anacardium excelsum , ascorbate, Calophyllum longifolium , chlorophyll a / b , Ficus insipida , photosynthetic pigments, Virola surinamensis .

References