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

• Published in: The New phytologist 2017-04, Vol.214 (2), p.585-596
• Main Authors: Peguero-Pina, José Javier, Siso, Sergio, Flexas, Jaume, Galmes, Jeroni, Garcia-Nogales, Ana, Niinemets, Ülo, Sancho-Knapik, Domingo, Saz, Miguel Ángel, Gil-Pelegrin, Eustaquio
• Format: Article
• Language: English
• Subjects: Adaptation; anatomical adaptations; Area; Capacity; Carbon dioxide; Carbon fixation; Chloroplasts; Climate; Conductance; Geography; Leaf area; leaf mass per area (LMA); Leaves; Limiting factors; Mediterranean Region; Mediterranean‐type climate; Mesophyll; Mesophyll Cells - cytology; Mesophyll Cells - physiology; mesophyll conductance (gm); Morphology; Photosynthesis; Plant Stomata - physiology; Plants (botany); Quercus; Quercus - cytology; Quercus - physiology; Resistance; sclerophylly; Species; Species Specificity; Stomata; Stomatal conductance
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/nph.14406

Leaf mass per area (LMA) has been suggested to negatively affect the mesophyll conductance to CO2 (g m), which is the most limiting factor for area-based photosynthesis (A N) in many Mediterranean sclerophyll species. However, despite their high LMA, these species have similar A N to plants from other biomes. Variations in other leaf anatomical traits, such as mesophyll and chloroplast surface area exposed to intercellular air space (S m/S and S c/S), may offset the restrictions imposed by high LMA in g m and A N 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 N 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 m, the most limiting factor for carbon assimilation in these species. Species with higher A N showed increased S c/S, which implies increased g m without changes in stomatal conductance. The occurrence of this anatomical adaptation at the cell level allowed evergreen oaks to reach A N values comparable to congeneric deciduous species despite their higher LMA.