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Mechanism for photoprotection of leaves at the bolling stage under field conditions in Gossypium barbadense and G. hirsutum

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Author(s): ZHANG Ya-Li | LUO Yi | YAO He-Sheng | TIAN Jing-Shan | LUO Hong-Hai | ZHANG Wang-Feng

Journal: Chinese Journal of Plant Ecology
ISSN 1005-264X

Volume: 34;
Issue: 10;
Start page: 1204;
Date: 2010;

Keywords: leaf movement | photoinhibition | photosynthesis | pima cotton | upland cotton

ABSTRACT
Aims Our principal aim was to test the hypothesis that pima cotton (Gossypium barbadense) and upland cotton (G. hirsutum) have different photoinhibition and photoprotection strategies due to differences in light capturing and photosynthetic characteristics.Methods We measured diurnal leaf movement, incident photon flux density (PFD) on leaves, leaf temperature, maximal photochemical efficiency of PSII (Fv/Fm), PSII photochemical efficiency (Ī¦PSII), electron transport rate (ETR), photochemical quenching coefficient (qP), non-photochemical quenching (NPQ), net photosynthetic rate (Pn), stomatal conductance (Gs) and photorespiration (Pr) in pima and upland cotton.Important findings Upland cotton had higher Pn and Gs than pima cotton. Nevertheless, the ratio of photorespiration rate to gross photosynthetic rate was generally higher in pima cotton. Pima cotton and upland cotton had similar degrees of photoinhibition. Furthermore, pima cotton had generally higher thermal energy dissipation capacity than upland cotton. All results indicated that differences in leaf diaheliotropic movement and Gs in pima cotton and upland cotton resulted in differences of both incident PFD on leaves and leaf temperature. Upland cotton and pima cotton preferentially used electron transport flux and thermal energy dissipation, respectively, for light energy dissipation toward photoprotection to against photoinhibition. Nevertheless, more electron transport flux was distributed into the photorespiration pathway to prevent over-reduction of the photosynthetic electrontransport chain and photoinhibition in pima cotton.

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