Text by Lauri Laanisto
In the latest number of Tree Physiology, volume 36, issue 3 (link to Table of Contents), Ülo has managed to be the author or co-author for three papers. Two of them, Ülo´s commentary piece titled “Does the touch of cold make evergreen leaves tougher?” (link to blog post) (link to full text); and Peguero-Pina et al paper “Leaf functional plasticity decreases the water consumption without further consequences for carbon uptake in Quercus coccifera L. under Mediterranean conditions.” (link to blog post) (link to full text) have already been covered in this blog.
So this leaves the third paper, which is another study led by(this guy has three first author papers in this Tree Physiology issue alone!), titled “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″.
It´s a simple experiment (well, I mean philosophically, not technically…) that shows, for the first time, how one species of fir exhibits structural changes in the needles when growing in contrasting light conditions, while the other species of fir does not. Which one is which – read it yourself!
Full citation: 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.