Quantitative effects of environmental variation on stomatal anatomy and gas exchange in a grass model

Abstract

Stomata are cellular pores on the leaf epidermis that allow plants to regulate carbon assimilation and water loss. Stomata integrate environmental signals to regulate pore apertures and adapt gas exchange to fluctuating conditions. Here, we quantified intraspecific plasticity of stomatal gas exchange and anatomy in response to seasonal variation in Brachypodium distachyon. Over the course of 2 years, we (a) used infrared gas analysis to assess light response kinetics of 120 Bd21-3 wild-type individuals in an environmentally fluctuating greenhouse and (b) microscopically determined the seasonal variability of stomatal anatomy in a subset of these plants. We observed systemic environmental effects on gas exchange measurements and remarkable intraspecific plasticity of stomatal anatomical traits. To reliably link anatomical variation to gas exchange, we adjusted anatomical gsmax calculations for grass stomatal morphology. We propose that systemic effects and variability in stomatal anatomy should be accounted for in long-term gas exchange studies.

Opposite polarity programs regulate asymmetric subsidiary cell divisions in grasses

“…We found that both single mutants and the double mutant bdpolar-1;bdpan1-1 showed lower absolute stomatal conductance ( g sw ; Figure 5A, C and E ) that seemed proportional to the number of aberrantly formed SCs. This was not linked to reduced stomatal density ( Figure 5—figure supplement 1A ) but rather stomatal size ( Figure 5—figure supplement 1B ), as GCs without SCs tend to be shorter and accordingly have shorter pores ( Nunes et al, 2022 ). In contrast, the analysis of relative g sw (values normalised to maximum stomatal conductance per genotype and individual), which visualises differences in stomatal opening and closing kinetics, showed slower stomatal movements in the double mutant only ( Figure 5B, D and F ; Figure 5—figure supplement 1C, D, E ).…”

“…This could be due to fewer SCs being defective in bdpolar-1;bdpan1-1 (82%) compared to bdmute (almost 100%), which also results in a reduced effect on GC size and shape. Also, bdmute shows lower stomatal density (~30% of stomata abort), which is correlated with slower stomatal kinetics in B. distachyon ( Nunes et al, 2022 ). Alternatively, and unlike in bdmute , wrongly divided SCs in bdpolar-1;bdpan1-1 might have acquired and retained residual SC identity thus expressing appropriate ion channels, signalling modules or cell wall modifiers, which could positively influence stomatal kinetics.…”

“…Leaf-level gas exchange measurements were performed as described in Nunes et al, 2022 . In short, LI-6800 Portable Photosynthesis System (Li-COR Biosciences Inc) was used to measure the youngest, fully expanded leaf (17–21 days after sowing).…”

“…Five individuals each genotype bdpolar-1 , bdpan1-1 , bdpolar-1;bdpan1-1, and five individual WTs were measured. Stomatal opening and closure speed were evaluated by rate constants (k, min –1 ) determined from exponential equations fitted for each of the three light transitions (1000–100, 100–1000, and 1000–0 PAR), as described in Nunes et al, 2022 .…”

Stomatal Ratio Showing No Response to Light Intensity in Oryza

“…In amphistomatous, it was suggested that stomata developed independently on the two surfaces [ 27 ]. Studies have shown that stomata on two leaf sides respond differently to environmental changes in some species [ 28 ] and the stomatal density ratio of the abaxial and adaxial surface, termed the stomatal ratio, was observed to vary with growth environments in many species [ 27 , 29 , 30 ]. Again, these studies focused mostly on eudicot species, and the field has largely ignored monocots.…”