The key role of cell walls in setting mesophyll conductance to CO2 (gm) and, consequently, photosynthesis, is reviewed. First, the theoretical properties of cell walls that can affect gm are presented. Then, we focus on cell wall thickness (Tcw) reviewing empirical evidence showing that Tcw varies strongly among species and phylogenetic groups in a way that correlates with gm and photosynthesis i.e. the thicker the mesophyll cell walls, the lower gm and photosynthesis. Potential interplays of gm, Tcw, dehydration tolerance and hydraulic properties of leaves are also discussed. Dynamic variations of Tcw in response to the environment and their implications in the regulation of photosynthesis are discussed, and recent evidence suggesting an influence of cell wall composition on gm are presented. We then propose a hypothetical mechanism for the influence of cell walls on photosynthesis, combining the effects of thickness and composition, particularly pectins. Finally, we discuss the prospects for using biotechnology for enhancing photosynthesis by means of altering cell wall-related genes.
Under drought conditions, leaf photosynthesis is limited by the supply of CO2 . Drought induces production of abscisic acid (ABA), and ABA decreases stomatal conductance (gs ). Previous papers reported that the drought stress also causes the decrease in mesophyll conductance (gm ). However, the relationships between ABA content and gm are unclear. We investigated the responses of gm to the leaf ABA content [(ABA)L ] using an ABA-deficient mutant, aba1, and the wild type (WT) of Nicotiana plumbaginifolia. We also measured leaf water potential (ΨL ) because leaf hydraulics may be related to gm . Under drought conditions, gm decreased with the increase in (ABA)L in WT, whereas both (ABA)L and gm were unchanged by the drought treatment in aba1. Exogenously applied ABA decreased gm in both WT and aba1 in a dose-dependent manner. ΨL in WT was decreased by the drought treatment to -0.7 MPa, whereas ΨL in aba1 was around -0.8 MPa even under the well-watered conditions and unchanged by the drought treatment. From these results, we conclude that the increase in (ABA)L is crucial for the decrease in gm under drought conditions. We discuss possible relationships between the decrease in gm and changes in the leaf hydraulics.
Summary β-Cyclocitral (β-CC) is a volatile compound deriving from 1 O 2 oxidation of β-carotene in plant leaves. β-CC elicits a retrograde signal, modulating 1 O 2 -responsive genes and enhancing tolerance to photooxidative stress. Here, we show that β-CC is converted into water-soluble β-cyclocitric acid (β-CCA) in leaves. This metabolite is a signal that enhances plant tolerance to drought by a mechanism different from known responses such as stomatal closure, osmotic potential adjustment, and jasmonate signaling. This action of β-CCA is a conserved mechanism, being observed in various plant species, and it does not fully overlap with the β-CC-dependent signaling, indicating that β-CCA induces only a branch of β-CC signaling. Overexpressing SCARECROW-LIKE14 (SCL14, a regulator of xenobiotic detoxification) increased drought tolerance and potentiated the protective effect of β-CCA, showing the involvement of the SCL14-dependent detoxification in the phenomenon. β-CCA is a bioactive apocarotenoid that could potentially be used to protect crop plants against drought.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.