Photosynthetic responses of four tropical tree species grown under gap and understorey conditions in a semi-deciduous forest

Abstract

− (Photosynthetic responses of four tropical tree species grown under gap and understorey conditions in a semi-deciduous forest). Leaf CO 2 assimilation (A) as a function of photosynthetic photon flux density (Q) or intercellular Co 2 concentration (Ci) and chlorophyll fluorescence measurements were carried out on four tropical woody species growing in forest gap and understorey (Bauhinia forficata link. and Guazuma ulmifolia lam. as pioneers, and Hymenaea courbaril l. and Esenbeckia leiocarpa Engl. as non-pioneers). Chlorophyll fluorescence indicated similar acclimation capacities of photochemical apparatus to contrasting light environments irrespective to plant species. Maximum CO 2 assimilation and quantum yield derived from A/Q curves indicated higher photosynthetic capacity in pioneer than in non-pioneer species in forest gap. However, the differences among species did not show a straightforward relation with their successional status regarding data derived from A/Q curves under understorey conditions. Both successional groups are able to sustain positive carbon balance under contrasting natural light availabilities, modifying photochemical and biochemical photosynthetic traits with similar phenotypic plasticity capacity.Key words -acclimation, chlorophyll fluorescence, forest succession, leaf gas exchange, photosynthetic response curves RESUMO − (Respostas fotossintéticas de quatro espécies tropicais arbóreas crescidas sob condições de clareira e de sub-bosque em uma floresta semi-decídua). A assimilação de CO 2 (A) em função da densidade de fluxo de fótons fotossintéticos (Q) ou da concentração intercelular de CO 2 (Ci), e medidas de fluorescência da clorofila foram realizadas em quatro espécies tropicais arbóreas em uma clareira e um sub-bosque (Bauhinia forficata link. e Guazuma ulmifolia Lam. como espécies pioneiras, e Hymenaea courbaril l. e Esenbeckia leiocarpa Engl. como espécies não pioneiras). Os dados de fluorescência da clorofila indicaram que ambos os grupos mostraram capacidade similar de aclimatação do aparato fotoquímico independente do ambiente luminoso. A assimilação máxima de CO 2 e a eficiência quântica derivadas das curvas A/Q indicaram maior capacidade fotossintéticas das espécies pioneiras do que as não-pioneiras na clareira. Entretanto, sob condições de sub-bosque, as diferenças observadas em relação às curvas A/Q não mostraram uma relação direta com o grupo funcional das espécies. Ambos os grupos da sucessão foram capazes de manter um balanço de carbono positivo sob disponibilidades de luz contrastantes, modificando as características fotoquímicas e bioquímicas da fotossíntese com capacidade de plasticidade fenotípica similar.Palavras-chave -aclimatação, curvas de resposta fotossintética, florescência da clorofila, trocas gasosas foliares, sucessão florestal 1.

Special issue in honour of Prof. Reto J. Strasser - Chlorophyll a fluorescence of Bertholletia excelsa Bonpl. plantations under thinning, liming, and phosphorus fertilization

“…Thus, the increase in DI0/RC after thinning may be the main factor that led the remaining trees to reduce FV/FM ratio from 0.83 to 0.72 and the PIABS from 1.7 to 0.8. This association between DI0/RC and photochemical efficiency (FV/FM and PIABS) has been previously demonstrated by Boisvert et al (2006) and Souza et al (2010). However, our results indicate that liming and P fertilization alleviate the effects of high light stress after thinning.…”

Space-Temporal Dynamics of Endemic Tree Species in Secondary Forest in the Atlantic Forest Domain in Brazil

“…There was a predominance of pioneer and initial secondary species, but there was also the emergence of late secondary species. Although with few individuals, the occurrence of LS in these sites can be partially explained by the photosynthetic plasticity and ability of these individuals to acclimatize to environments with variation in radiation availability, mainly in semideciduous forests (Martins et al, 2008;Souza et al, 2010;Pezzopane et al, 2018).…”

Carbon sequestration: mathematical model of the Brazilian Atlantic Forest.

“…The classification of species into groups is particularly necessary in the BAF because many species are represented by only a few individuals (Swaine and Whitmore, 1988). Even if the classification implies a degree of simplification that diminishes information content, it allows general patterns and consequently helps to predict the plant community response to environmental changes without demanding precise information from each species (Reich et al, 2003;Souza et al, 2010).…”