Data/hora: 11/06/2024 06:30:04

Provedor de dados: 	61	
País: 	Brazil	
Título: 	Energetic flux and performance index in copaiba (Copaifera multijuga Hayne) and mahogany (Swietenia macrophylla King) seedlings grown under two irradiance environments	
Autores: 	Gonçalves,José F.C.; Santos Jr.,Ulysses M.; Nina Jr.,Adamir R.; Chevreuil,Larissa R.	
Data: 	2007-09-01	
Ano: 	2007	
Palavras-chave: 	Chlorophyll a fluorescence; Energy fluxes in photosystem II; Light acclimation; O-J-I-P transients; Tropical tree species.	
Resumo: 	Plant adaptation under conditions of limited irradiance can be investigated by their efficiency while using the available energy with a minimal thermodynamic energy loss. For this reason, we compared the energetic fluxes and the performance index (PI ABS) in copaiba (Copaifera multijuga) and mahogany (Swietenia macrophyla) seedlings under both sunlight and shade. The experiment was carried out in Manaus (3º8'S, 59º52'W), Amazonas State, Brazil. The fluorescence transients were obtained in intact and healthy leaves using a Plant Efficiency Analyser (PEA) between 1200 h and 1300 h. Using the O-J-I-P test, the following parameters were calculated: 1) density of reaction centers per cross section (RC/CS), 2) maximum quantum yield for primary photochemistry of photosystem II (sigmaPo), and 3) probability of energy excitation (psio) or that of an absorbed photon (sigmaEo) to move an electron further than quinone A, and 4) the performance index (PI ABS). The highest PI ABS was found in seedlings under shade for both species. Mahogany seedlings exhibited values of PI ABS about three-fold and 14-fold higher than copaiba seedlings under shade and sunlight, respectively. For RC/CS, reaction centers were inactive under sunlight, 58% for mahogany and 78% for copaiba. The high irradiance induced a decrease of sigmaPo in mahogany (36%) and in copaiba (69%) when compared to shaded seedlings. This likely was a result of need for excess energy dissipation under sunlight. In addition, it was verified that seedlings under sunlight presented a severe decrease in sigmaEo, particularly in copaiba (23-fold), when compared to mahogany (9fold). Therefore, mahogany seedlings showed the highest performance in energy use under low and high irradiance, thus it may be proposed that mahogany presented lower entropy than copaiba seedlings, as demonstrated by the higher plasticity in the use of energy.	
Tipo: 	Info:eu-repo/semantics/article	
Idioma: 	Inglês	
Identificador: 	http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1677-04202007000300001	
Editor: 	Brazilian Journal of Plant Physiology	
Relação: 	10.1590/S1677-04202007000300001	
Formato: 	text/html	
Fonte: 	Brazilian Journal of Plant Physiology  v.19 n.3 2007	
Fonte: 	info:eu-repo/semantics/openAccess