The effect of growth irradiance on leaf anatomy and photosynthesis in maple species

Abstract

The capacity in using irradiance is decisive for the success of tree species in forests. Tree species that have different capacities in using irradiance are classified as light-adapted and shade-tolerant species. When grown under low or high light, these species sometimes show contrast photosynthetic response, which indicates that the changes in the processes that limit photosynthesis may differ between these two types. We compared the leaf morphological and physiological acclimation to growth irradiance among the three maple species having different light adaptation. Seedlings of sun-adapted (Acer rufinerve), intermediate (Acer mono), and shade-adapted (Acer palmatum) maple species were grown under 100% and 17% of full sun. When grown under full sun, thickness of mesophyll and surface area of chloroplasts facing to intercellular airspaces (Sc) were larger in A. rufinerve compared to A. mono and A. palmatum. In contrast, interspecific difference in light-saturated photosynthesis (Amax) was not significant. CO2 partial pressure at the carboxylation site (Cc) was lower in A. rufinerve compared to those in A. palmatum and A. mono, because both stomatal and mesophyll conductance to CO2 diffusion were tended to be small in this species. This low Cc in A. rufinerve may minimize the increase of Amax irrespective of large Rubisco contents. On the other hand, A. rufinerve had large water use efficiency (WUE) compared to the other species, which may be advantageous under full sun where midday VPD would be large. Under low growth irradiance, interspecific difference in leaf anatomy and photosynthesis was less significant compared to full sun.