Abstract
Efficient acclimation to different growth light intensities is essential for plant fitness. So far, most studies on light acclimation have been conducted with plants grown under different constant light regimes, but more recent work indicated that acclimation to fluctuating light or field conditions may result in different physiological properties of plants. Thale cress (Arabidopsis thaliana) was grown under three different constant light intensities (LL: 25 μmol photons m−2 s−1; NL: 100 μmol photons m−2 s−1; HL: 500 μmol photons m−2 s−1) and under natural fluctuating light (NatL) conditions. We performed a thorough characterization of the morphological, physiological, and biochemical properties focusing on photo-protective mechanisms. Our analyses corroborated the known properties of LL, NL, and HL plants. NatL plants, however, were found to combine characteristics of both LL and HL grown plants, leading to efficient and unique light utilization capacities. Strikingly, the high energy dissipation capacity of NatL plants correlated with increased dynamics of thylakoid membrane reorganization upon short-term acclimation to excess light. We conclude that the thylakoid membrane organization and particularly the light-dependent and reversible unstacking of grana membranes likely represent key factors that provide the basis for the high acclimation capacity of NatL grown plants to rapidly changing light intensities.
Highlights
Efficient acclimation to changing environmental conditions is a prerequisite for the survival and competitiveness of plants in the field
Plants grown under constant high light conditions showed increased growth compared to those grown under constant low light as judged from the phenotype of 6 week-old plants (Figure 1A)
In contrast to all other plants, natural fluctuating light (NatL) plants already developed flowers after 6 weeks (Figure 1A), indicating that NatL conditions triggered a faster plant development. This was supported by analysis of the fresh weight (FW) per cm2 leaf area, which increased from about 10 mg in low light (LL) plants to 25 mg in high light (HL) plants, whereas NatL plants showed highest values of about 30 mg (Figure 1B)
Summary
Efficient acclimation to changing environmental conditions is a prerequisite for the survival and competitiveness of plants in the field. Long-term acclimation to either low light (LL) or high light (HL) conditions occurs in the time range of days to months and involves—among others—adjustments of leaf architecture, chloroplast structure, composition of the photosynthetic electron transport chain, and regulation of photosynthetic light utilization (Boardman, 1977; Anderson, 1986; Schoettler and Toth, 2014). (6) Higher energy dissipation capacity (Brugnoli et al, 1994; Demmig-Adams and Adams, 1996; Park et al, 1996; Ballottari et al, 2007; Mishra et al, 2012) These characteristics apply to extreme sun and shade plants in the field, to sun, and shade leaves of the same individual plant in the field and to plants grown under different controlled light conditions in the lab. PsbS acts as a sensor of the lumen pH (Li et al, 2004) and is supposed to activate qE by conformational changes in PSII antenna proteins (Horton et al, 2005) through the interaction with LHCII complexes (Correa-Galvis et al, 2016; Sacharz et al, 2017)
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