Study of short-term plasticity in two contrasting genotypes of Populus nigra L.

Species like black poplar characterized by an indeterminate growth, can acclimate to the changing environmental conditions during the seasons through a modification of morphological and physiological features. The acclimation results fundamental for the increasing evapo-transpirative demand and water availability. In this perspective, each generation of leaf becomes an indicator of physiologic performance, determining the short-term plasticity (acclimation) of a genotype to different environmental conditions. The main objective of this work is to analyse the physiological adjustment by morphological and physiological features of leaves in two contrasting genotypes of P. nigra, growing in a common environment. The mesic genotype 58-861 (Northern Italy) reacts to the increasing dry conditions keeping constantly higher values of ?13C while the xeric genotype Poli (Southern Italy) shows lower values, despite no significant differences in the gas exchanges. Morphological and stomatal leaf traits were the main drivers of the different behaviour in the two genotypes to face the "temporal" environment, but different from the provenance. In particular the results, especially in the development phases, demonstrate how phenotypic plasticity is evident at seasonal scale, playing a role for the success of an indeterminate-growing species. They could also be generalized for similar experiments and could support further investigation about short-term plasticity.