In the present chapter, we review the current state-of-the-art of knowledge on mesophyll (internal) CO₂ diffusion conductance of photosynthetic tissues (for simplification, g_m). We show that, despite concerns regarding the methodological approaches currently used for its estimation, a large and consistent body of evidence has accumulated showing that g_m is finite and significantly limiting for photosynthesis, as well as being highly variable among photosynthetic organisms and in response to environmental changes. Part of this variation results from different anatomies of the photosynthetic tissues, with a particularly strong influence of chloroplast distribution and cell wall thickness. Besides these, it appears that a biochemical modulation of g_m also occurs, likely involving aquaporins and, possibly, carbonic anhydrases and other metabolic components.

Further efforts are needed in the near future to improve CO₂ diffusion models, both for the estimation of g_m and for the precise physiological understanding of the CO₂ assimilation process in different plants, as well as to increase our knowledge of the mechanistic base for g_m and its regulation.

Item Type:	Research Book Chapter
Keywords:	CO2, diffusion, photosynthesis, photosynthetic organs, mesophyll conductance, phylogeny, aquaporins, cell wall thickness
Research Division:	Biological Sciences
Research Group:	Plant biology
Research Field:	Plant physiology
Objective Division:	Plant Production and Plant Primary Products
Objective Group:	Other plant production and plant primary products
Objective Field:	Other plant production and plant primary products not elsewhere classified
UTAS Author:	Carriqui, M (Mr Marc Carriqui Alcover)
ID Code:	134466
Year Published:	2018
Deposited By:	Plant Science
Deposited On:	2019-08-14
Last Modified:	2019-10-07
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