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

Text by Lauri Laanisto

Another study by from the Mediterranean. Peguero-Pina has collaborated with Ülo seveal times before, and also regarding the physiology of oaks (link to blog post). This time the study does not focus on a single species, but seven Quercus species; and not all of them from the the Mediterranean, but some from Mediterranean as well. The importance of mesophyll conductance in photosynthesis is a topic that has been covered a lot in this blog, so I will not go deep into it here (click on the relevant tags if you´re interested). It seems that from the theoretical and methodological point of view this paper here did not do anything spectacular. The novel part was that they measured the traits from not one, but several species. At least that is what they conclude themselves: “To the best of our knowledge, this is the first interspecific comparison of photosynthetic characteristics and underlying leaf anatomical traits among Mediterranean oaks from Europe/North Africa and North America.” Of course, it was rather surprising that species from the same genus had such differences between these traits. I would suggest that in addition to interspecific comparison, these things need to be studied also in the context of intraspecific variability (which seems, at least for me, to be one of the understated areas in ecophysiological and physiological studies…) – just a single population (10 individuals) from each species was studied in this case.

Citation: Peguero‐Pina, J. J., Sisó, S., Flexas, J., Galmés, J., García‐Nogales, A., Niinemets, Ü., … & Gil‐Pelegrín, E. (2017). Cell‐level anatomical characteristics explain high mesophyll conductance and photosynthetic capacity in sclerophyllous Mediterranean oaks. New Phytologist, DOI: 10.1111/nph.14406 (link to full text)

dehesa_los_valhondos_jamon_beher_bernardo_hernandez_salamanca_pelayos

Dehesa – Oak-dominated savanna-like semi-natural ecosystems in the Mediterranean (pic from here)

Abstract:

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