Photosynthetic induction in leaves of co-occurring Fagus lucida and Castanopsis lamontii saplings grown in contrasting light environments |
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Authors: | Kun-dong Bai De-bao Liao De-bing Jiang Kun-fang Cao |
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Affiliation: | (1) Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Kunming, 650223, Yunnan, China;(2) Graduate School of Chinese Academy of Sciences, Beijing, 100039, China;(3) Guangxi Miao’ershan Mountain National Nature Reserve, Guilin, 541316, Guangxi Zhuang Autonomous Region, China |
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Abstract: | Photosynthetic induction times and photoinhibition in relation to simulated sunflecks (sudden increase of irradiance from 20 to 1,500 μmol m−2 s−1) were examined in leaves of co-occurring Fagus lucida (a deciduous tree) and Castanopsis lamontii (an evergreen tree) saplings grown either in a beech forest understory or in an adjacent open site during a late rainy season. Two hypotheses were tested: (1) understory leaves would display faster photosynthetic induction times and greater photoinhibition than open-grown leaves; and (2) evergreen species would have slower photosynthetic induction times and lighter photoinhibition than deciduous species. Times to reach 90% of maximal CO2 assimilation rate (t 90%A ) and stomatal conductance did not differ between species, but showed faster by 3–5 min in open-grown leaves than understory leaves due to higher initial stomatal conductance (g s initial) and induction state 1 min into simulated sunflecks (IS1min) in the former. Our analysis across the published data on photosynthetic induction of 48 broad-leaved woody species again revealed the negative correlations between t 90%A and either g s initial or IS1min, and the similarity of t 90%A and between evergreen and deciduous species. Measurements of maximum PSII photochemical efficiency (F v/F m) indicated that photoinhibition occurred in saplings in any of the growth habitats during sunfleck-induced photosynthetic induction. Despite no interspecific differences in the degree of photoinhibition, understory leaves of both species suffered heavier photoinhibition than open-grown leaves, as indicated by a stronger decrease of F v/F m in the former. Dynamic changes in the quantum yields of PSII photochemistry and ΔpH- and xanthophyll-regulated thermal dissipation and adjustments in the partitioning of electron flow between assimilative and non-assimilative processes were functional to resist photoinhibition. However, such photoinhibition, together with stomatal and biochemical limitations, would decrease carbon gain during simulated sunflecks, particularly in understory leaves. |
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Keywords: | Photosynthetic induction Fagus lucida Castanopsis lamontii Photoinhibition Sunfleck |
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