Photosynthesis and chlorophyll a fluorescence during flag leaf senescence of field-grown wheat plants

Qingtao Lu, Congming Lu*, Jianhua ZHANG, Tingyun Kuang

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review

84 Citations (Scopus)


The characteristics of photosynthetic gas exchange, chlorophyll a fluorescence, and xanthophyll cycle pigments during flag leaf senescence of field-grown wheat plants were investigated. With senescence progressing, the light-saturated net CO2 assimilation rate expressed either on a basis of leaf area or chlorophyll decreased significantly. The apparent quantum yield of net photosynthesis decreased when expressed on a leaf area basis but increased when expressed on a chlorophyll basis. The maximal efficiency of PSII photochemislry decreased very little while actual PSII efficiency, photochemical quenching, and the efficiency of excitation capture by open PSII centers decreased considerably. At the same time, non-photochemical quenching increased significantly. A substantial decrease in the contents of violaxanthin and zeaxanthin, but a slight decrease in the content of antheraxanthin were observed. However, the de-epoxidation status of the xanthophyll cycle was positively correlated with progressive senescence. This increase was due mainly to a smaller decrease in zeaxanthin than in violaxanthin. Our results suggest that PSII apparatus remained functional, but a down-regulation of PSII occurred under the steady state of photosynthesis in senescent flag leaves. Such a down-regulation was associated with the closure of PSII centers and an enhanced xanthophyll cycle-related thermal dissipation in the PSII antennae.

Original languageEnglish
Pages (from-to)1173-1178
Number of pages6
JournalJournal of Plant Physiology
Issue number11
Publication statusPublished - 1 Nov 2002

Scopus Subject Areas

  • Physiology
  • Agronomy and Crop Science
  • Plant Science

User-Defined Keywords

  • Chlorophyll a fluorescence
  • Photosynthesis
  • Photosystem II photochemistry
  • Wheat (Triticum aestivum L.)
  • Xanthophyll cycle


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