Stomatal Biology of CAM Plants

Abstract

ORCID ID: 0000-0001-9899-8101 (J.M.).Crassulacean acid metabolism (CAM) is a major physiological syndrome that has evolved independently in numerous land plant lineages. CAM plants are of great ecological significance, and there is increasing interest for their water-use efficiency and drought resistance. Integral to the improvement in water-use efficiency that CAM affords is a unique pattern of stomatal conductance, distinguished by primarily nocturnal opening and often extensive diurnal flexibility in response to environmental factors. Here, we assess how recent research has shed new light on the functional biology of CAM plant stomata and integration within the broader physiology and ecology of succulent organisms. Divergences in stomatal sensitivity to environmental and endogenous factors relative to C 3 species have been a key aspect of the evolution of functional CAM. Stomatal traits of CAM plants are closely coordinated with other leaf functional traits, and structural specialization of CAM stomatal complexes may be of undiagnosed functional relevance. We also highlight how salient results from ongoing work on C 3 plant stomatal biology could apply to CAM species. Key questions remaining relate to the interdependence between stomatal and mesophyll responses and are particularly relevant for bioengineering of CAM traits or bioenergy crops to exploit enhanced water-use efficiency and productivity on marginal land. With the increasing availability of powerful analytical tools and the emergence of new model systems for the study of the molecular basis of physiological traits in CAM plants, many exciting avenues for future research are open to intrepid investigators.

Small Pores with a Big Impact

“…These boundaries remain open to debate, as noted by Hõrak et al (2017) and by Cai et al (2017). The questions surface again in the context of Crassulacean acid metabolism stomata in the Update review by Males and Griffiths (2017) Guard cells arise from the surrounding epidermal pavement cells as the leaf expands. Here, too, they present a model for cellular organization and differentiation that incorporates a wealth of nonlinearities, beginning with the asymmetry in cell division that gives rise to the guard mother cell.…”

“…Inoue and Kinoshita (2017) discuss recent advances in dissecting the mechanisms behind lightmediated regulation of the H 1 -ATPases that energize the guard cell plasma membrane. The reviews by Males and Griffiths (2017) and Santelia and Lunn (2017) encapsulate the several exciting new developments that point to a complex coupling between carbohydrate metabolism and membrane transport in guard cells as well as its relationship to photosynthesis in the underlying mesophyll of leaves. Stomata are also points of access for pathogens to these delicate, nutrient-filled tissues.…”

Ethylene Exerts Species-Specific and Age-Dependent Control of Photosynthesis

“…Photosynthesis is intimately linked with stomatal conductance, which mediates CO 2 uptake and 111 transpiration Vialet-Chabrand et al, 2017;Males & Griffiths, 2017). Ethylene 112 treatment by ethylene gas, ACC, or ethephon induces stomatal closure in Arabidopsis (Desikan et al, 113 2006).…”

Review and in silico analysis of fermentation, bioenergy, fiber, and biopolymer genes of biotechnological interest inAgaveL. for genetic improvement and biocatalysis

“…The soluble sugars from the assimilation of CO 2 in the dark are essential for the light period following . Although, CAM metabolism is present in a wide variety of species with distinct phylogenetic lineages and hábitats, all these species developed diverse structures and adaptations to stressful environments but they all share anatomical and functional traits …”

“…Closing of stomata is one of the physiological mechanisms plants use for facing water deficit, therefore maintaining their water status. Stomatal conductance is a function of the density, size, and opening of stomata present in each plant species . In the genus Agave , groups of 3–5 stomata are arranged in short rows and it is known that stomatal densities vary according to ploidy level of accessions; a phenomenon know as “gigas.” Comparing different ploidy level accessions from the same species of Agave , those with higher ploidy level ( A. angustifolia Haw.…”