Responses of Photosynthetic Electron Transport to Drought and Re-watering in Two Maize Genotypes
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Responses of Photosynthetic Electron Transport to Drought and Re-watering in Two Maize Genotypes J. Liua, H. J. Lia, Y. Y. Guoa, G. X. Wanga, H. J. Zhanga, R. H. Zhanga,*, and W. H. Xub,** a
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College of Agronomy, Northwest A&F University, Yangling Shaanxi, 712100 China Laboratory of Forest Ecology and Management. Shenyang Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, 110016 China *e-mail: [email protected] **e-mail: [email protected] Received November 11, 2019; revised January 2, 2020; accepted January 16, 2020
Abstract—Effects of drought stress on photosynthesis have been well-documented. However, photosynthetic electron transport process in response to combined drought stress and recovery in maize is relatively scant. In this study, the photosynthetic electron flow, the energy quenching in PSII and PSI, and cyclic electron flow (CEF) activity in two maize (Zea mays L.) genotypes were measured. In both genotypes, chlorophyll a fluorescence transient (OJIP) showed progressive drought caused increases of J and I step, the positive of K-band and L-band; and decreases in TR0/ABS, ET0/TR0, ET0/ABS, RE0/ET0 and PIABS. Analysis of the modulated 820 nm reflection (MR) showed progressive drought decreased the values of VPSI and VPSII-PSI. Decreases in quantum yields of Y(I) and Y(II) were accompanied by increase of Y(NPQ) and CEF. Compare to Shaanke9 (SK9), the drought-induced changes in Dafeng30 (DF30) were stronger, and SK9 kept higher CEF under drought stress. After re-watering, SK9 recovered more completely in all parameters than DF30, suggesting that the reversible down-regulation of PSII and PSI in SK9 maintained the functional integrity of photosystems. The photosynthetic apparatus of SK9 cultivar is more resistant to drought than that of DF30. These results indicate that more efficient regulation of photosynthetic electron transport between two photosystems and higher CEF in the SK9 jointly play crucial role in recovery from drought damages, which could contribute to a better adaptation under varying drought environment. Keywords: Zea mays, drought stress, re-watering, photosystem I, photosystem II, photosynthetic electron transport, cyclic electron flow DOI: 10.1134/S1021443720050088
INTRODUCTION Maize (Zea mays L.) is a widely cultivated food crop in arid and semiarid region such as Northwest China. Maize is often subjected to varying degrees of drought in Abbreviations: ABS/RC—measure of the average total absorbance per active PSII RC; CEF—cyclic electron flow; ET0/TR0 —probability (at t0) that the trapped exciton moves an electron into the electron transport chain beyond Q−A ; ET0/ABS—quantum yield for electron transport; F0 – minimal fluorescence of the dark-adapted state; FI—fluorescence at I step; FJ—fluorescence at J step; FK—fluorescence at K step; FL —fluorescence at L step; FP—maximal fluorescence of the darkadapted state; Ft—fluorescence at time t after onset of actinic illumination; K-band—fluorescence at K step; L-band—fluorescence at L step; LEF—linear
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