BRIEF COMMUNICATIONPhotosynthetic light-response curves of light-demanding and shade-tolerant seedlings of neotropical tree species

Abstract

Light-response curves of seedlings of five light-demanding (LD) and four shade-tolerant (ST) neotropical tree species, native to the Brazilian Atlantic biome, were analyzed, aiming to verify differences between these functional groups regarding the light use. We hypothesized that variations in the light requirement of seedlings would occur not only between LD and ST species, but also within these functional groups. The apparent quantum yield of CO2 assimilation, dark respiration rate (RD), photorespiration rate (RP), light-compensation point (Icomp), light-saturation point (Imax), and light-saturated photosynthetic rate (PNmax) were estimated from fitted light-responses curves and using equations available in the literature. The results revealed great differences between the functional groups. RD, RP, Icomp, Imax, and PNmax were effectively higher in the LD than those in the ST species. Furthermore, a continuum of strategies regarding the light use was observed, matching with some ecological characteristics of the species studied here.

Keywords

• early-successional species; gas exchange; late-successional species; photosynthetic photon flux density.