Photosynthesis regulation during leaf ontogeny progenies of Hevea brasiliensis and Hevea pauciflora grown under two water conditions

Abstract

Chlorophyll synthesis, stomatal behaviour and CO₂ balance were studied during the period of leaf ontogeny in seedlings of H. brasiliensis (lAN 873) and H. pauciflora grown under two water conditions. When submitted to a water stress H. pauciflora was able to maintain higher and more stable water potentials (Ψ_w) than other species. Reduction in photosynthesis rates in water stressed plants was associated to a drop in Ψ_w in both species. This reduction in H. brasiliensis was related to a decreasing 50% in chlorophyll synthesis and an increase in stomatal resistance. Under water stress H. pauciflora showed only an enhancement in the rates of photorespiration.