Drought Induced Damages of Photosynthesis in Bean and Plantain Plants Analyzed in vivo by Chlorophyll a Fluorescence

V. Krasteva, V. Alexandrov, M. Chepisheva, S. Dambov, D. Stefanov, I. Yordanov and V. Goltsev
St Kliment Ohridsky Sofia University, Department Biophysics and Radiobiology, BG – 1164 Sofia, Bulgaria

Abstract

Krasteva, V., V. Alexandrov, M. Chepisheva, S. Dambov, D. Stefanov, I. Yordanov and V. Goltsev, 2013. Drought induced damages of photosynthesis in bean and plantain plants analyzed in vivo by chlorophyll a fluorescence. Bulg. J. Agric. Sci., Supplement 2, 19: 39–44

 

Plant uses complex responses to protect against drought, including changes in gene expression, cell metabolism and whole plant physiology. Drought affects photosynthetic apparatus at different levels of organization. Using of new developed techniques for simultaneous registration of prompt and delayed fluorescence, give opportunity to achieve substantial progress in investigation of the drought effects on photosynthesis in intact leaves. The stress reaction of photosynthetic machinery is monitored in leaves of whole plants of Phaseolus vulgaris and Plantago major during 12-days cessation of irrigation. In opposite to drought sensitive bean plants subjected to 12-day drought treatment, photosynthetic apparatus of plantain reveals earlier response to increasing water deficit. It was expressed by a visible decrease in fluorescence yield and suppression of photosynthetic efficiency. The shape of delayed fluorescence induction is found to be the most sensitive indicator for changes in photosynthetic electron transport in plants subjected to drought stress. As a parameter for estimation of drought stress effects could be considered the second maximum of sub-millisecond delayed fluorescence induction curve, while both microsecond and millisecond delayed fluorescence components did not change significantly. The changes of the second delayed fluorescence induction maximum could be interpreted as decreased rate of intersystem electron flow in tolerant Plantago plants. This suggestion is also supported by significant decrease in the rate of P700+ reduction that was monitored by light reflection at 820 nm. We proposed that intersystem electron transport suppression could be related to adjustment of electron transport chain for following switch to cyclic electron flow around Photosystem I to secure photosynthetic electron transport with protection against drought-induced damages.

Key words: chlorophyll a fluorescence, delayed fluorescence, drought stress
Abbreviations: PF – prompt fluorescence; DF – delayed fluorescence; Fm – maximal prompt fluorescence; DF0.1 – DF measurements during dark intervals of 0.02–0.09 ms; DF1.0 – DF measurements were registered during dark intervals of 0.1–0.9 ms; DF2.3 – DF measurements were registered during dark intervals of 1.0 ms to 2.3 ms; MR820 – modulated 820 nm reflection; P700 – the first electron donor in PS I reaction center; RWC – relative water content; Apot photosynthetic metabolic potential; Multifunctional Plant Efficiency Analyser – M-PEA; QА and QВ – the first and second quinone acceptors in PSII; РQ – plastoquinone.

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