The changes of chlorophyll fluorescence parameters of medicago sativa under drought stress and recovery after it

Abstract

Drought is one of the major causes for crop loss worldwide. Responses to drought are multiple and consistent. It is well established that drought stress impairs numerous metabolic and physiological processes in plants. It leads to growth reduction, reduction in the content of chlorophyll pigments and water, and changes in fluorescence parameters. The aim of this study was to investigate the response of chlorophyll a fluorescence parameters of lucerne (Medicago sativa) under partly regulated environment and drought stress effect. Plants were grown in pots filled with a mixture of field soil, perlite and fine sand (volume ratio 5:3:2) in the greenhouse of Vytautas Magnus university in 2020. Drought stress lasted one week, after that plants were left for one week recovery period. Under drought effect grown plants were watered only 50 % of norm during exposure time. Chlorophyll a fluorescence parameters measurements were taken with the Plant Efficiency Analyser, PEA (Hansatech Instruments, Ltd., King’s Lynn, Norfolk, England) with randomly selected youngest fully expanded leaves on the last (7th) day of the exposure of drought and after recovery. Drought stress statistically significant decreased several investigated chlorophyll a fluorescence parameters. The changes of Fv/Fm, which is an indicator of the efficiency of second photosystem (PSII), were statistically insignificant during both experiment stages. The increase of specific energy flux per reaction centre (RC) for absorption ABS/RC was followed by an increase of trapping energy (TRo/SCo) under drought stress effect. The efficiency with which an electron can move from the reduced intersystem electron acceptors to the PSI and electron acceptors (delta(Ro)) was lower under drought stress. Higher energy usage under drought stress also indicated slightly decreased values of dissipated energy flux per cross section (DIo/CSo). After the recovery period [...]