Photosynthesis and Leaf Nutrient Contents in Ochroma Pyramidale(Bombacaceae)

In Ochroma pyramidale(Cav. exLam.) Urb., photon-saturated photosynthetic capacity (PNmax) was 13 μmol(CO2) m−2s−1. Average stomatal conductance (gs) and water-use efficiency (WUE) were greater at high irradiance, about 260 mmol(H2O) m−2s−1and 2.15 g(C) kg−1(H2O), respectively. In the dark, gsvalues were about 30% of maximum gs. Leaf nutrient contents on a leaf area basis were 131, 15, 36, 21, and 12 mmol m−2for N, P, K, Ca, and Mg, respectively. Ochromaalso accumulated a greater amount of soluble saccharides than starch, 128 versus90 g kg−1(DM). The availability of N and Mg, but not P, Ca, or K, may limit photosynthetic rates of Ochromain this site.