The effects of different daily irradiance profiles on Arabidopsis growth, with special attention to the role of PsbS

Abstract

In nature, light is never constant, while in the controlled environments used for vertical farming, in vitro propagation, or plant production for scientific research, light intensity is often kept constant during the photoperiod. To investigate the effects on plant growth of varying irradiance during the photoperiod, we grew Arabidopsis thaliana under three irradiance profiles: a square-wave profile, a parabolic profile with gradually increasing and subsequently decreasing irradiance, and a regime comprised of rapid fluctuations in irradiance. The daily integral of irradiance was the same for all three treatments. Leaf area, plant growth rate, and biomass at time of harvest were compared. Plants grown under the parabolic profile had the highest growth rate and biomass. This could be explained by a higher average light-use efficiency for carbon dioxide fixation. Furthermore, we compared the growth of wild type plants with that of the PsbS-deficient mutant npq4. PsbS triggers the fast non-photochemical quenching process (qE) that protects PSII from photodamage during sudden increases in irradiance. Based mainly on field and greenhouse experiments, the current consensus is that npq4 mutants grow more slowly in fluctuating light. However, our data show that this is not the case for several forms of fluctuating light conditions under otherwise identical controlled-climate room conditions.

An open-source controller to build a dynamic light intensity setup

“…The systems we have developed can be particularly useful in photosynthesis research, where there is a growing interest in understanding the effects of fluctuating light on photosynthesis. To date the method described in this study has been used in three distinct research projects in which changes in growth light pattern were shown to affect photosynthesis and plant development [ 27 – 29 ]. In the first investigation, differing profiles of irradiance, each providing the same daily integral of irradiance, were compared.…”

“…Three different light growth conditions, one sinusoidal, one square wave, and one fluctuating were tested on a panel of different Arabidopsis thaliana genotypes. The sinusoidal light regime was shown to improve shoot biomass in comparison to square wave light regimes [ 27 ]. In the other two projects, the effect of specific allelic variation in different environmental conditions was assessed using Arabidopsis thaliana genotypes grown in a range of constant and fluctuating light conditions.…”