From reproduction to production, stomata are the master regulators

Abstract

Summary The best predictor of leaf level photosynthetic rate is the porosity of the leaf surface, as determined by the number and aperture of stomata on the leaf. This remarkable correlation between stomatal porosity (or diffusive conductance to water vapour gs) and CO2 assimilation rate (A) applies to all major lineages of vascular plants (Figure 1) and is sufficiently predictable that it provides the basis for the model most widely used to predict water and CO2 fluxes from leaves and canopies. Yet the Ball–Berry formulation is only a phenomenological approximation that captures the emergent character of stomatal behaviour. Progressing to a more mechanistic prediction of plant gas exchange is challenging because of the diversity of biological components regulating stomatal action. These processes are the product of more than 400 million years of co‐evolution between stomatal, vascular and photosynthetic tissues. Both molecular and structural components link the abiotic world of the whole plant with the turgor pressure of the epidermis and guard cells, which ultimately determine stomatal pore size and porosity to water and CO2 exchange (New Phytol., 168, 2005, 275). In this review we seek to simplify stomatal behaviour by using an evolutionary perspective to understand the principal selective pressures involved in stomatal evolution, thus identifying the primary regulators of stomatal aperture. We start by considering the adaptive process that has locked together the regulation of water and carbon fluxes in vascular plants, finally examining specific evidence for evolution in the proteins responsible for regulating guard cell turgor.

The physiology of drought stress in grapevine: towards an integrative definition of drought tolerance

“…(ii) Stomatal regulation, one of the most widely studied traits impacting drought tolerance. It is expressed as the g s –Ψ leaf curve and indicates the maximal photosynthetic capacity ( Medrano et al , 2003 ; Brodribb et al , 2020 ) as well as the critical Ψ leaf that plants are trying to avoid ( Meinzer et al , 2009 ; Choat et al , 2018 ). The latter could be used to calculate the soil water reservoir that is available to the vine (in combination with root volume and the soil water retention curve).…”

When everything changes at once: finding a new normal after genome duplication

“…An increase in guard cell size may have tremendous impacts on the biology of a plant. Guard cells are epidermal cells that flank stomata, the pores in the leaf surface that allow gas exchange and are thus essential for energy production via photosynthesis [56,57]. Guard cells are very commonly larger in both new and evolved polyploids (table 1; electronic supplementary material, table S1), though there is evidence from comparing neo-and established tetraploids of several species that while there is a large shift in guard cell size triggered by WGD, established polyploids exhibit guard cells of intermediate size, indicating a reduction over time [41,54], suggesting this may in part be a 'type A' trait (figure 2).…”

Stomatal density and mechanics are critical for high productivity: insights from amphibious ferns

“…In addition to differences in the density and size of stomata, differences in stomatal regulation across the lineages of land plants may have been instrumental in shaping land plant evolution (Brodribb et al, 2009(Brodribb et al, , 2020. Angiosperm species have comprehensively described, sophisticated stomatal responses to changes in multiple wavelengths of light, atmospheric CO 2 , hormones and water availability (Assmann & Jegla, 2016;McAdam et al, 2016b;Hiyama et al, 2017;Sussmilch et al, 2019b;Lawson & Matthews, 2020;Brodribb et al, 2020). An ongoing debate seeks to differentiate between a model of gradualistic evolution, which proposes that these stomatal control modules emerged incrementally over the past 400 Myr, and a model of evolutionary conservation, which proposes that these modules were present in the precursors of all land plants.…”