Abies pinsapo or the Spanish fir has been a long-term study object for Mediterranean forest researchers, plant ecologists and ecophysiologists already since the 1960s. As our boss, Ülo, has had long and fruitful collaboration with Spanish researchers, he usually co-authors at least one tree ecophysiology paper about the Spanish fir per year.
In 2012 it was: Peguero-Pina, José Javier; Flexas, Jaume; Galmés, Jeroni; Niinemets, Ülo; Sancho-Knapik, Domingo; Barredo, Gonzalo; Villarroya, Dido; Gil-Pelegrín, Eustaquio (2012). Leaf anatomical properties in relation to differences in mesophyll conductance to CO2 and photosynthesis in two related Mediterranean Abies species. Plant, Cell and Environment, 35(12), 2121 – 2129. (link to full text)
Last year´s yield was: Sancho-Knapik, Domingo; Peguero-Pina, José Javier; Flexas, Jaume; Herbette, Stéphane; Cochard, Hervé; Niinemets, Ülo; Gil-Pelegrín, Eustaquio (2014). Coping with low light under high atmospheric dryness: shade acclimation in a Mediterranean conifer (Abies pinsapo Boiss.). Tree Physiology, 34(12), 1321 – 1333. (link to full text)
And now, fresh off the press is: Peguero-Pina, J. J., Sancho-Knapik, D., Flexas, J., Galmés, J., Niinemets, Ü., & Gil-Pelegrín, E. (2015). Light acclimation of photosynthesis in two closely related firs (Abies pinsapo Boiss. and Abies alba Mill.): the role of leaf anatomy and mesophyll conductance to CO2. Tree physiology, tpv114. (link to full text)
Leaves growing in the forest understory usually present a decreased mesophyll conductance (gm) and photosynthetic capacity. The role of leaf anatomy in determining the variability in gm among species is known, but there is a lack of information on how the acclimation of gm to shade conditions is driven by changes in leaf anatomy. Within this context, we demonstrated that Abies pinsapo Boiss. experienced profound modifications in needle anatomy to drastic changes in light availability that ultimately led to differential photosynthetic performance between trees grown in the open field and in the forest understory. In contrast to A. pinsapo, its congeneric Abies alba Mill. did not show differences either in needle anatomy or in photosynthetic parameters between trees grown in the open field and in the forest understory. The increased gm values found in trees of A. pinsapo grown in the open field can be explained by occurrence of stomata at both needle sides (amphistomatous needles), increased chloroplast surface area exposed to intercellular airspace, decreased cell wall thickness and, especially, decreased chloroplast thickness. To the best of our knowledge, the role of such drastic changes in ultrastructural needle anatomy in explaining the response of gm to the light environment has not been demonstrated in field conditions.