Phtosynthetic traits of seedlings of several tree species in an Amazonian Forest

Abstract

Photosynthetic properties of the Amazonian forest tree species, Cedrela odorata, Swietenia macrophylla, and Aniba rosaeodora, were studied in a nursery and in an open field to assess their potential success for planting purposes. These species were compared with nursery grown Ochroma lagopus Sw. and Dipteryx odorata. In the nursery, light-saturated net photosynthetic rate (Amax) and maximum stomatal conductance (gsmax) were highest in O. lagopus, a fast growing and light demanding plant, and lowest in D. odorata, a slowgrowing and shade tolerant species. Amax and gsmax were relatively high in C. odorata, which is medium to fast growing and has intermediate light requirements. Low Amax of A. rosaeodora suggests that this species may be classified as a slow growing species. In the open field, Amax and gsmax were highest in C. odorata, followed by S. macrophylla, and lowest in A. rosaeodora. Water use efficiency of A. rosaeodora was lower than that of C. odorata and S. macrophylla. Stomatal closure of C. odorata and S. macrophylla under high leaf-to-air vapor pressure difference (VPDL) enabled these species to avoid excessive water loss, but A. rosaeodora appeared not to avoid excessive water loss. These inferior photosynthetic properties of A. rosaeodora may explain it’s high mortality and slow growth in the open and, thus, this species is not suitable for open planting. Both Amax and gsmax of the open planted seedlings were higher than those of the nursery seedlings, while specific leaf area (SLA, leaf area per unit leaf dry weight) was smaller in the open planted seedlings than in the nursery seedlings, suggesting that the leaves of the nursery seedlings were shade-adapted while the open planted seedlings developed sun-adapted leaves. In order to enhance acclimation to exposed conditions, we recommend hardening the seedlings by exposing them to full sunlight before planting them in the open.