Abstract
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 CO2 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.
Original language | English |
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Pages (from-to) | 239-247 |
Number of pages | 9 |
Journal | Physiologia Plantarum |
Volume | 104 |
Issue number | 2 |
DOIs | |
Publication status | Published - Oct 1998 |
Scopus Subject Areas
- Physiology
- Genetics
- Plant Science
- Cell Biology
User-Defined Keywords
- Chlorophyll fluorescence
- Excitation energy dissipation
- Leaf senescence
- Photosynthesis
- Photosystem II
- Triticum aestivum
- Wheat