Time-course of photosynthetic induction in four tropical woody species grown in contrasting irradiance habitats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

We investigated the photosynthetic induction time-course in species of different ecological groups grown in contrasting forest irradiance environments, gap and understorey, exposed to different darkness times in order to verify the plant capacity to exploit irradiance heterogeneity. Photosynthetic induction was studied in leaves of Bauhinia forficata and Guazuma ulmifolia (early succession species, ES), and Esenbeckia leiocarpa and Hymenaea courbaril (late succession species, LS). T(50) and T(90) (time estimates to attain 50 and 90 % of maximum net photosynthetic rate, respectively) varied according to the time of previous exposure to darkness and growth irradiance. In both darkness times of 10 and 30 min, T(50) was lower in the LS-than ES-species. These results, jointly with significant higher induction state of the leaves after 10 min of darkness, suggest that the LS-species has a higher potential to sunfleck utilization compared to ES-species, both grown in the understorey. After 10 and 30 min of darkness the differences between ecological groups were not clearly detected in the gap for T(50) and T(90), indicating that eco-physiological characteristics of each ecological group did not influence the induction time of the species evaluated herein. Thus the capacity to show phenotypic plasticity is not exclusive to an ecological group, but it is rather a more intrinsic feature related to the differential capacity of individuals.