Photosynthesis and water relations of well-watered orange plants as affected by winter and summer conditions

Autor(es)

Ribeiro, R. V. ^[1] ; Machado, E. C. ^[1] ; Santos, M. G. ^[2] ; Oliveira, R. F. ^[3]

Afiliação do(s) autor(es)

^[1] Inst Agron Estado Sao Paulo, Ctr Res & Dev Ecophysiol & Biophys, Sect Plant Physiol, BR-13012970 Campinas, SP - Brazil

^[2] Univ Fed Pernambuco, Dept Bot, BR-50670901 Recife, PE - Brazil

^[3] Univ Sao Paulo, Dept Biol Sci, Luiz de Queiroz Coll Agr, BR-13418900 Piracicaba, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Photosynthetica; v. 47, n. 2, p. 215-222, JUN 2009.
• Citações Web of Science: 55

Resumo

The aim of this study was to evaluate how the summer and winter conditions affect the photosynthesis and water relations of well-watered orange trees, considering the diurnal changes in leaf gas exchange, chlorophyll (Chl) fluorescence, and leaf water potential (I) of potted-plants growing in a subtropical climate. The diurnal pattern of photosynthesis in young citrus trees was not significantly affected by the environmental changes when compared the summer and winter seasons. However, citrus plants showed higher photosynthetic performance in summer, when plants fixed 2.9 times more CO(2) during the diurnal period than in the winter season. Curiously, the winter conditions were more favorable to photosynthesis of citrus plants, when considering the air temperature (< 29 A degrees C), leaf-to-air vapor pressure difference (< 2.4 kPa) and photon flux density (maximum values near light saturation) during the diurnal period. Therefore, low night temperature was the main environmental element changing the photosynthetic performance and water relations of well-watered plants during winter. Lower whole-plant hydraulic conductance, lower shoot hydration and lower stomatal conductance were noticed during winter when compared to the summer season. In winter, higher ratio between the apparent electron transport rate and leaf CO(2) assimilation was verified in afternoon, indicating reduction in electron use efficiency by photosynthesis. The high radiation loading in the summer season did not impair the citrus photochemistry, being photoprotective mechanisms active. Such mechanisms were related to increases in the heat dissipation of excessive light energy at the PSII level and to other metabolic processes consuming electrons, which impede the citrus photoinhibition under high light conditions. (AU)

• Processo FAPESP: 05/57862-8 - Florescimento e frutificação em laranjeira Valência: aspectos anatômicos, fisiológicos, bioquímicos e moleculares
• Beneficiário: Marcelo Carnier Dornelas
• Modalidade de apoio: Auxílio à Pesquisa - Temático
• Processo FAPESP: 02/08480-7 - Variação sazonal da fotossíntese, relações hídricas e do teor de carboidratos em laranjeira Valência
• Beneficiário: Rafael Vasconcelos Ribeiro
• Modalidade de apoio: Bolsas no Brasil - Doutorado