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Changes in photosystem II function during senescence of wheat leaves
Author(s) -
Lu Congming,
Zhang Jianhua
Publication year - 1998
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1034/j.1399-3054.1998.1040212.x
Subject(s) - photosystem ii , photosynthesis , senescence , chlorophyll fluorescence , quenching (fluorescence) , electron transport chain , photochemistry , quantum yield , chemistry , chlorophyll , kinetics , photosynthetic reaction centre , photosystem , fluorescence , biophysics , biology , botany , biochemistry , microbiology and biotechnology , physics , quantum mechanics
Analyses of chlorophyll fluorescence were undertaken to investigate the alterations in photosystem II (PSII) function during senescence of wheat ( Triticum aestivum L. cv. Shannong 229) leaves. Senescence resulted in a decrease in the apparent quantum yield of photosynthesis and the maximal CO 2 assimilation capacity. Analyses of fluorescence quenching under steady‐state photosynthesis showed that senescence also resulted in a significant decrease in the efficiency of excitation energy capture by open PSII reaction centers (F' v /F' m ) but only a slight decrease in the maximum efficiency of PSII photochemistry (F' v /F' m ). At the same time, a significant increase in non‐photochemical quenching (q N ) and a considerable decrease in photochemical quenching (q P ) were observed in senescing leaves. Rapid fluorescence induction kinetics indicated a decrease in the rate of Q A reduction and an increase in the proportion of Q B ‐non‐reducing PSII reaction during senescence. The decrease in both F' v /F' m and q P explained the decrease in the actual quantum yield of PSII electron transport ((φ PSII ). We suggest that the modifications in PSII function, which led to the down‐regulation of photosynthetic electron transport, would be in concert with the lower demand for ATP and NADPH in the Calvin cycle which is often inhibited in senescing leaves.