Stomatal density affects gas diffusion and CO2 assimilation dynamics in Arabidopsis under fluctuating light

Stomatal density (SD) is closely associated with photosynthetic and growth characteristics in plants. In the field, light intensity can fluctuate drastically throughout a day. The objective of the present study is to examine how the change in SD affects stomatal conductance (gs) and CO2 assimilation rate (A) dynamics, biomass production, and water use under fluctuating light. Here, we compared the photosynthetic and growth characteristics under constant and fluctuating light among four lines of Arabidopsis thaliana (L.): a wild-type (WT), a STOMAGEN/EPFL9-overexpressing line, STOMAGEN/EPFL9-silencing line, and an EPIDERMAL PATTERNING FACTOR 1 knockout line (epf1). Lower SD resulted in faster response of A owing to the faster response of gs to fluctuating light and higher water use efficiency without decreasing A. Higher SD resulted in a faster response of A because of the higher initial gs. epf1, with a moderate increase in SD, showed the larger carbon gain, attributable to the high capacity and fast response of A, yielding higher biomass production than WT under fluctuating light. The present study suggests that higher SD can be beneficial to improve biomass production in the plant under field conditions.