Cyclic electron flow plays an important role in photoprotection for the resurrection plant <Emphasis Type="Italic">Paraboea</Emphasis><Emphasis Type="Italic">rufescens</Emphasis> under drought stress |
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Authors: | Wei Huang Shi-Jian Yang Shi-Bao Zhang Jiao-Lin Zhang Kun-Fang Cao |
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Institution: | (1) Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, 666303 Yunnan, China;(2) School of Life Science, University of Science and Technology of China, Hefei, 230027 Anhui, China;(3) Graduate University, Chinese Academy of Sciences, 100049 Beijing, China; |
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Abstract: | Resurrection plants could survive severe drought stress, but the underlying mechanism for protecting their photosynthetic
apparatus against drought stress is unclear. Cyclic electron flow (CEF) has been documented as a crucial mechanism for photoprotection
in Arabidopsis and tobacco. We hypothesized that CEF plays an important role in protecting photosystem I (PSI) and photosystem II (PSII)
against drought stress for resurrection plants. To address this hypothesis, the effects of mild drought stress on light energy
distribution in PSII and P700 redox state were examined in a resurrection plant Paraboea
rufescens. Cyclic electron flow was not activated below the photosynthetic photon flux density (PPFD) of 400 μmol m−2 s−1 in leaves without drought stress. However, CEF was activated under low light in leaves with mild drought stress, and the
effective quantum yield of PSII significantly decreased. Meanwhile, non-photochemical quenching (NPQ) was significantly stimulated
not only under high light but also under low light. Compared with the control, the fraction of overall P700 that cannot be
oxidized in a given state (PSI acceptor side limitation) under high light was maintained at low level of 0.1 in leaves with
water deficit, indicating that the over-reduction of the PSI acceptor side was prevented by the significant stimulation of
CEF. Furthermore, methyl viologen could significantly increase the PSII photo-inhibition induced by high light compared with
chloramphenicol. These results suggested that CEF is an important mechanism for protecting PSI and PSII from drought stress
in resurrection plants. |
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