Characterizing the diurnal decrease in photosystem II operating efficiency

Rapid increases in light intensity that exceed the capacity of photosynthesis can result in the inactivation of the reaction centres of the photosystems (PS) in leaves. Plants can acclimate to such changing light conditions, which is highlighted by the morphological and physiological differences between plants grown under constant and fluctuating daylight regimes. However, it seems that even under a constant and moderate light intensity, PSII operating efficiency can decrease throughout the photoperiod, which reduces photosynthesis and light use efficiency. During the photoperiod, processes such as photoassimilate accumulation and PSII damage negatively impact photosynthesis and reduce PSII efficiency. In vertical farms and greenhouses, the light use efficiency may therefore decrease throughout the day, and lighting recipes should include this temporal response to achieve higher efficiency. Therefore, a better understanding of the temporal effects of light regimes and intensity on PSII efficiency (e.g. damage rate, recovery rate) is important to optimize lighting recipes. For example, if plants can quickly re-increase their light use efficiency after a period of low-light intensity, novel light recipes with a low light intensity recovery period to optimize light use efficiency over the diurnal period can be developed.
Using chlorophyll a fluorescence, it is possible to monitor PSII operating efficiency, non-photochemical quenching and photoinhibition during the photoperiod, under different light regimes. The aim is to quantify the temporal decrease of PSII operating efficiency and identify lighting regimes that could maintain higher light use efficiency over the diurnal period. For this experiment, you may use species such as tomato or lettuce.

Used skills

  • Performing climate chamber experiments
  • Chlorophyll a fluorescence measurement
  • Data analysis

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