Concentration of photosynthetic pigments and chlorophyll fluorescence of mahogany and tonka bean under two light environments

Abstract

This study was carried out in a plantation of a degraded area in Central Amazon, Brazil, in order to assess environmental light effects on leaf pigment concentrations and chlorophyll a fluorescence in mahogany (Swietenia macrophylla King) and tonka bean (Dipteryx odorata Aubl. Willd). Three-year old saplings were grown in an open site (sun) with maximum radiation of approximately 2000 mumol m-2 s-1 and under the shade of a Ochroma pyramidale (Cav. ex Lam. Urb) canopy. A leaf area index of 2.46 was optically determined for the Ochroma foliage with 13% of full sunlight (maximum radiation about 260 mumol m-2 s-1). Carotenoid and chlorophyll concentrations were spectrophotometrically determined. Initial (Fo), maximum (Fm) and variable fluorescence (Fv) were determined with a portable fluorometer. Chlorophyll concentrations (Chl a, Chl b and Chl tot) on a fresh mass basis were greater in shade leaves than in sun acclimated leaves in both species. On the other hand, when comparisons were made on a per area basis, Chl a concentrations were greater in the sun than in shade leaves of tonka bean. In contrast, Chl b concentrations were higher in the shade environment for this species. No differences were observed in Chl concentrations per unit area in mahogany leaves. Carotenoid concentrations were higher for sun-acclimated leaves of mahogany, both on a per unit area and on a fresh mass basis. In tonka bean, higher carotenoid concentrations in shade leaves were only observed on a fresh weight basis. No differences were found between environments when carotenoid concentrations were expressed as a function of leaf area. Fluorescence variables (Fo, Fm, and Fv) were greater in sun leaves than in shade leaves of mahogany. In contrast, Fv and Fm, but not Fo, values were higher in shade acclimated leaves than in full sunlight-adapted leaves of tonka bean. However, there was a higher Fv/Fm ratio value for tonka bean in sunlight environments. We conclude that these species, classified as mid and late successional species, differ markedly regarding the utilization of photosynthetic pigments, increasing either light harvesting efficiency at low irradiance or protection against photosynthetic machinery damage in higher solar radiation environments.

Fluorescência e teores de clorofilas em abacaxizeiro cv. pérola submetido a diferentes concentrações de sulfato de amônio

“…Em relação ao fluxo luminoso (densidade de fluxo de fótons), trabalhando com espécies arbóreas, Dias e Marenco (2007) encontraram decréscimos na F 0 ao transferir plantas de menor para maior fluxo luminoso e, em temperaturas diferentes, sugerem que a redução é devida a dano na proteína D1 do PSII. Gonçalves et al (2001) encontraram valores elevados de F 0 e diferenças significativas para F 0 entre plantas de mogno (Swietenia macrophylla King), crescidas ao sol e à sombra.…”

“…Esta invariabilidade nos teores de clorofila a nos tratamentos com 15; 30 e 60 mg/kg pode refletir-se na manutenção da captura de luz pelo sistema antena dos fotossistemas I e II e na capacidade de transferência de elétrons na cadeia fotossintética (HUANG et al, 2004).…”

“…Tal razão oscilou entre 2,249 mg.g -1 nas plantas tratadas com 15 mg/kg de SA e 2,883 mg.g -1 nas plantas tratada com 60 mg/kg, valores característicos de plantas crescidas em condições de baixa intensidade luminosa (GONÇALVES et al, 2001).…”

Características funcionais de folhas de sol e sombra de espécies arbóreas em uma mata de galeria no Distrito Federal, Brasil

“…Por outro lado folhas de sol e sombra não se diferenciaram nas concentrações foliares de nitrogênio e dos outros macronutrientes, expressos em termos de massa ou área. Uma elevada capacidade de transporte de elétrons aliada a uma melhor fotoproteção são comumente encontradas em folhas de ambientes com alta luminosidade (Gonçalves et al 2001, ou mesmo em plantas crescendo sob altas irradiâncias (Maia et al 2009). No presente estudo, foi observado que folhas de sol apresentaram um maior rendimento quântico do FSII aliado a uma maior proporção de centros de reação do FSII abertos (conforme indicado pela variável qL) e maior condutância estomática.…”

Differential physiological and biochemical responses under variable culture conditions in micro-propagated Solenostemon scutellarioides: an important ornamental plant

“…The total chlorophyll a/b concentration was calculated as previously described. 22 The ex vitro establishment of different plant lines were done as similar described in previous section.…”