Photosynthetic characteristic and leaf traits variations along a natural light gradient in Acer campestre and Crataegus monogyna

Abstract

Variations in leaf traits at anatomical, morphological and physiological level were assessed in Acer campestre L. and Crataegus monogyna Jacq. plants in a forest understory-gap-edge light gradient inside a broadleaf deciduous forest. The relative changes of the considered parameters monitored in the two species were compared in terms of intraspecific plasticity. Overall, both species were able to acclimatize to the natural light gradient with different light regime (i.e. low light, medium light and high light), through an integrated response at the three analyzed levels. However, some differences in intraspecific plasticity were detected related to the different shade-tolerance of these species. In particular, the investigated species showed significantly differences in plasticity at morphological level (i.e. leaf area and specific leaf area) with A. campestre having a greater morphological plasticity related to its greater shade-tolerance compared to C. monogyna. At the physiological level, differences in intraspecific plasticity have been identified for those parameters describing a higher drought susceptibility in high light regime (i.e. dark respiration rate, maximum PSII photochemical efficiency and actual quantum yield of photosynthesis) suggesting that A. campestre was less capable to acclimatize to these conditions, thus confirming the trade-off between drought and shade-tolerance.