Photosynthesis and leaf nutrient contents in Ochroma pyramidale (Bombacaceae)

Abstract

In Ochroma pyramidale (Cav. ex Lam.) Urb., photon-saturated photosynthetic capacity (PNmax) was 13 μmol(CO2) m-2 s-1. Average stomatal conductance (gs) and water-use efficiency (WUE) were greater at high irradiance, about 260 mmol(H2O) m-2 s-1 and 2.15 g(C) kg-1(H2O), respectively. In the dark, gs values were about 30 % of maximum gs. Leaf nutrient contents on a leaf area basis were 131, 15, 36, 21, and 12 mmol m-2 for N, P, K, Ca, and Mg, respectively. Ochroma also accumulated a greater amount of soluble saccharides than starch, 128 versus 90 g kg-1(DM). The availability of N and Mg, but not P, Ca, or K, may limit photosynthetic rates of Ochroma in this site.