Morphological and anatomical determinants of mesophyll conductance in wild relatives of tomato (Solanum sect. Lycopersicon, sect. Lycopersicoides; Solanaceae)

Abstract

Natural selection on photosynthetic performance is a primary factor determining leaf phenotypes. The complex CO2 diffusion path from substomatal cavities to the chloroplasts -the mesophyll conductance (gm) -limits photosynthetic rate in many species and hence shapes variation in leaf morphology and anatomy. Among sclerophyllous and succulent taxa, structural investment in leaves, measured as the leaf dry mass per area (LMA), has been implicated in decreased gm. However, in herbaceous taxa with high gm, it is less certain how LMA impacts CO2 diffusion and whether it significantly affects photosynthetic performance. We addressed these questions in the context of understanding the ecophysiological significance of leaf trait variation in wild tomatoes, a closely related group of herbaceous perennials. Although gm was high in wild tomatoes, variation in gm significantly affected photosynthesis. Even in these tenderleaved herbaceous species, greater LMA led to reduced gm. This relationship between gm and LMA is partially mediated by cell packing and leaf thickness, although amphistomy (equal distribution of stomata on both sides of the leaf) mitigates the effect of leaf thickness. Understanding the costs of increased LMA will inform future work on the adaptive significance of leaf trait variation across ecological gradients in wild tomatoes and other systems.

Vapour pressure deficit during growth has little impact on genotypic differences of transpiration efficiency at leaf and whole‐plant level: an example from Populus nigra L.

“…This fits to some extent with recent observations (Tholen & Zhu ; Muir et al . ) even if it is clear that tissue density is by far not the only determinant of g m .…”

A few enlarged chloroplasts are less efficient in photosynthesis than a large population of small chloroplasts in Arabidopsis thaliana

“…4) revealed that the decrease of mesophyll conductance is the most important factor limiting A in mutants. Mesophyll structural features, including T cell-wall , S m , and S c are believed to play a central role in determining g m 22, 24, 26, 31 . Using the 1-D anatomical model, we analyzed the impacts of leaf anatomical traits on mesophyll conductance by considering all major leaf anatomical traits as described by Tosens et al .…”

Heterogeneity of photosynthesis within leaves is associated with alteration of leaf structural features and leaf N content per leaf area in rice

“…Rapid changes in g m have been documented (Flexas et al 2008;Warren 2008); however, these g m changes vary with leaf structural parameters such as cell packing, shape and wall thickness Tomás et al 2013). The relationship between CO 2 diffusion processes and morphoanatomical traits has been well documented, and many related trade-offs have been described (Ocheltree et al 2012;Giuliani et al 2013;Tanaka et al 2013;Muir et al 2014). However, most of these results were obtained across species, cultivars or genetic stocks.…”