Data/hora: 24/06/2024 01:24:07

Biblioteca(s): | Embrapa Mandioca e Fruticultura.
Data corrente: | 19/03/2004
Data da última atualização: | 19/03/2004
Autoria: | HABERMANN, G.; MACHADO, E. C.; RODRIGUES, J. D.; MEDINA, C. L.
Afiliação: | Universidade Estadual Paulista.
Título: | CO2 assimilation, photosynthetic ligt response curves, and water relations of 'Pêra' sweet orange plants infected with Xylella fastidiosa.
Ano de publicação: | 2003
Fonte/Imprenta: | Brazilian Journal of Plant Physiology, Londrina, v. 15, n. 2, p. 79-87, 2003.
ISSN: | 1677-0420
Idioma: | Inglês
Conteúdo: | Plants with citrus variegated chlorosis (CVC), a disease caused by the xylem-limited bactéria Xylella fastidiosa, have leaves with water deficiency symptoms and are associated with decreases on the net photosynthesis and transpiration rates. Using healthy and CVC-affected 'Pêra' sweet orange plants on 'Rangpur' lime rootstock, the leaf gas exchange variables were measured with an open-gas portable photosynthesis system. All plants were watered and the leaf water potencial (Yw) was measured by isopiestic thermocouple  psychrometric technique. The net photosynthesis (A) vs. internal leaf CO2 concentration (A/Ci curves) was analyzed. The relative effect of stomatal resistance on photosynthesis (S%) and the estimation of carboxylation efficiency were calculated. The rates of photosynthesis and transpiration, stomatal conductance, and internal leaf CO2 concentration (Ci) were also  measured while varying the photosynthetic photon flux density (PPFD). The S% values were approximately 30% greater in infected plants when compared to healthy ones. The light compensation point for diseased plants was higher than in the healthy ones, and the saturation light point in plants with CVC was twofold lower. The lower Yw in diseased plants favours the hypothesis of xylem occlusion, which probably caused a lower water supply to the mesophyll, thus decreasing the photosynthesis and transpiration rates. Nevertheless, there was also a reduction in the photosynthetic metabolic activities,  represented by lower carboxylation efficiency and photochemical disturbances that were detected in diseased plants.
Palavras-Chave: | A/Ci curves; Citrus sinensis L; Osbeck; photosynthetic metabolism; photosynthetic photon flux density.
Thesaurus Nal: | citrus variegated chlorosis; stomata.
Categoria do assunto: | --
Registro original: | Embrapa Mandioca e Fruticultura (CNPMF)
Exemplares: | CNPMF - (20796-1) - ADP - AP - -- - 581.01 -  -  - DIS