Cell‐level anatomical characteristics explain high mesophyll conductance and photosynthetic capacity in sclerophyllous Mediterranean oaks

Abstract

Leaf mass per area (LMA) has been suggested to negatively affect the mesophyll conductance to CO (g ), which is the most limiting factor for area-based photosynthesis (A ) in many Mediterranean sclerophyll species. However, despite their high LMA, these species have similar A to plants from other biomes. Variations in other leaf anatomical traits, such as mesophyll and chloroplast surface area exposed to intercellular air space (S /S and S /S), may offset the restrictions imposed by high LMA in g and A in these species. Seven sclerophyllous Mediterranean oaks from Europe/North Africa and North America with contrasting LMA were compared in terms of morphological, anatomical and photosynthetic traits. Mediterranean oaks showed specific differences in A that go beyond the common morphological leaf traits reported for these species (reduced leaf area and thick leaves). These variations resulted mainly from the differences in g , the most limiting factor for carbon assimilation in these species. Species with higher A showed increased S /S, which implies increased g without changes in stomatal conductance. The occurrence of this anatomical adaptation at the cell level allowed evergreen oaks to reach A values comparable to congeneric deciduous species despite their higher LMA.

Population-Level Differentiation in Growth Rates and Leaf Traits in Seedlings of the Neotropical Live Oak Quercus oleoides Grown under Natural and Manipulated Precipitation Regimes

“…Similar results for SLA-thickness-A area -RGR relationships were found in our previous (greenhouse) study under both well-watered and dry treatments (Ramírez-Valiente and Cavender-Bares, 2017). Since leaf lamina thickness and mesophyll thickness are highly associated in oaks (e.g., Peguero-Pina et al, 2017), our results would support Niinemets (2015) hypothesis. “Multiple-trait” mixed models showed a significant effect of SLA on RGR even after taking A area into account.…”

Photoprotective Strategies of Mediterranean Plants in Relation to Morphological Traits and Natural Environmental Pressure: A Meta-Analytical Approach

“…These structures represent an example of evolutionary convergence. They reduce water loss (Peguero-Pina et al, 2017) and they may be highly reflective, limiting the penetration of light to the photosynthetic apparatus and reaching the mesophyll (Agrawal et al, 2009; Camarero et al, 2012). Thereby they reduce the need of photoprotective pigments and antioxidants, supporting the photoprotective role of leaf pubescence in Mediterranean species (Morales et al, 2002).…”

“…Despite structural filtering of light and efficient protection against water lost of most sclerophyllous leaves, it has been proposed the existence of a trade-off between photosynthesis and LMA in relation with Leaf Economics Spectrum (Wright et al, 2004). It seems that mesophyll conductance (g s ) may be the most limiting factor for carbon assimilation, showing those leaves with highest LMA values, a reduction in CO 2 diffusion to the carboxylation sites (Flexas et al, 2014; Onoda et al, 2017; Peguero-Pina et al, 2017). This implies that plants with high LMA will generally show lower photosynthetic capacity and thus, may require higher levels of photoprotective metabolites.…”

Drought‐introduced variability of mesophyll conductance in Gossypium and its relationship with leaf anatomy

“…Meanwhile, Evans et al () concluded that g ias is so large that it is not a major determinant of g m in leaves. Instead, T cw and S c /S, which affect g liq , were thought to be the most important factors in the determination of the g m (Evans et al , Miyazawa et al , Terashima et al , Tosens et al , Tomás et al , Onoda et al , Peguero‐Pina et al ). Studies have shown that the rate of CO 2 diffusion is determined by the relative length and the tortuosity and porosity of the medium (Flexas et al , Peguero‐Pina et al , Tosens et al , Nadal and Flexas ).…”