The roles of photochemical and non-photochemical quenching in regulating photosynthesis depend on the phases of fluctuating light conditions

Abstract

The induction and relaxation of photochemistry and non-photochemical quenching (NPQ) are not instantaneous and require time to respond to fluctuating environments. There is a lack of integrated understanding on how photochemistry and NPQ influence photosynthesis in fluctuating environments. We measured the induction and relaxation of chlorophyll a fluorescence and gas exchange in poplar and cotton at varying temperatures under saturating and fluctuating lights. When the light shifted from dark to high, the fraction of open reaction centers in photosystem II (qL) gradually increased while NPQ increased suddenly and then remained stable. Temperature significantly changed the response of qL but not that of NPQ during the dark to high light transition. Increased qL led to higher photosynthesis but their precise relationship was affected by NPQ and temperature. qL was significantly related to biochemical capacity. Thus, qL appears to be a strong indicator of the activation of carboxylase, leading to the similar dynamics between qL and photosynthesis. When the light shifted from high to low intensity, NPQ is still engaged at a high level, causing a stronger decline in photosynthesis. Our finding suggests that the dynamic effects of photochemistry and NPQ on photosynthesis depend on the phases of environmental fluctuations and interactive effects of light and temperature. Across the full spectra of light fluctuation, the slow induction of qL is a more important limiting factor than the slow relaxation of NPQ for photosynthesis in typical ranges of temperature for photosynthesis. The findings provided a new perspective to improve photosynthetic productivity with molecular biology under natural fluctuating environments.

WITHDRAWN: Effects of light intensity and quality on needle physiological and biochemical traits of eighteen-year-old Pinus koraiensis trees adapted long-period to real field environment

“…Nonphotochemical chlorophyll uorescence quenching (NPQ) is a process in which excess absorbed light energy is dissipated into heat (Ruban 2016). An experiment found that NPQ increased then remained stable when light shifted from dark to high (Han et al 2022), which showed its meaningfulness. In this study, NPQ of full-light needles was signi cantly (p < 0.05) higher than those under lower light, just like a previous experiment found in other evergreen species (Wyka et al 2007).…”

“…However, light intensity and quality are highly variable in space and time according to the time of day, season, geography, climate, and the position of a leaf within canopy (Murchie and Niyogi 2011; Han et al 2022; Cifuentes and Moreno 2022). At the bottom of a dense canopy, the photosynthetic photon ux density (PPFD) and R:FR (red light: far-red light ratio) can be much lesser than that under full light (Chazdon and Fetcher 1984;Way and Percy 2012).…”

Shedding light on the increased carbon uptake by a boreal forest under diffuse solar radiation across multiple scales

“…This result is consistent with other research conducted in Scots pine forests, which also found that mean understorey irradiance did not significantly differ between clear and overcast sky conditions, but that there was less variation in understorey radiation under overcast conditions (Messier & Puttonen, 1995). The duration and intensity of fluctuating light have been found to control enzyme activities, stomatal conductance and non‐photochemical quenching, all potentially reducing the efficiency of photosynthesis (Grieco et al., 2020; Han et al., 2022; Kaiser et al., 2018; Yamori et al., 2020).…”

Integrated application of bacterial carbonate precipitation and silicon nanoparticles enhances productivity, physiological attributes, and antioxidant defenses of wheat (Triticum aestivum L.) under semi-arid conditions

“…Photochemical quenching (qP) and non-photochemical quenching (NPQ) were determined as described by Han et al (2022) and Ruban and Wilson (2021) , respectively. Barrs and Weatherley’s (1962) method was used to measure the relative water content (RWC).…”