The Function of Chloroplastic NAD(P)H Dehydrogenase in Tobacco during Chilling Stress under Low Irradiance

Author: Li Xin-Guo   Duan Wei   Meng Qing-Wei   Zou Qi   Zhao Shi-Jie  

Publisher: Oxford University Press

ISSN: 0032-0781

Source: Plant and Cell Physiology, Vol.45, Iss.1, 2004-01, pp. : 103-108

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Abstract

The function of chloroplastic NAD(P)H dehydrogenase (NDH) was examined by comparing a tobacco transformant (ΔndhB) in which the ndhB gene had been disrupted with its wild type, upon exposure to chilling temperature (4°C) under low irradiance (100 µmol m–2 s–1 PFD). During the chilling stress, the maximum photochemical efficiency of PSII (Fv/Fm) decreased markedly in both the wild type and ΔndhB. However, both Fv/Fm and P700+, as well as the PSII-driven electron transport rate (ETR), in ΔndhB were lower than that in the wild type, implying that NDH-dependent cyclic electron flow around PSI functioned to protect the photosynthetic apparatus from chilling stress under low irradiance. Under the stress, non-photochemical quenching (NPQ), particularly the fast relaxing NPQ component (qf) and the de-epoxidized ratio of the xanthophyll cycle pigments, (A+Z)/(V+A+Z), were distinguishable in ΔndhB from those in the wild type. The lower NPQ in ΔndhB might be related to an inefficient proton gradient across thylakoid membranes (ΔpH) because of lacking an NDH-dependent cyclic electron flow around PSI at chilling temperature under low irradiance.

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