Revista Brasileira de Fruticultura (Mar 2010)
Variação da densidade de fluxo de seiva e do potencial hídrico foliar nas faces leste e oeste da copa de laranjeira 'Valência' Variation of sap flow density and leaf water potencial in the east and west side of the canopy of 'Valencia' sweet orange plant
Abstract
O objetivo deste trabalho foi avaliar a influência da variação diurna e sazonal dos fatores ambientais sobre a densidade de fluxo de seiva (DFS) e o potencial hídrico foliar (Ψf) nas faces leste e oeste da copa de laranjeiras 'Valência' em condições de sequeiro. Foram utilizadas três plantas para as avaliações, cujas linhas de plantio estavam orientadas no sentido norte-sul. As avaliações foram realizadas durante um dia, em cada época do ano: verão, outono, inverno e primavera. Os valores de potencial hídrico medidos antes do amanhecer variaram de -0,31 MPa, no dia 10-12-05, a -1,1 MPa, no dia 30-08-05, porém não houve diferença significativa entre as faces leste e oeste da copa. Já para o potencial hídrico medido às 14h 30, em todas as épocas avaliadas, a face oeste apresentou menores (pThis paper aimed to study the effect of diurnal and seasonal variation of the environmental factors on the sap flow density (SFD) and leaf water potential (Ψl) in the east and west side of the canopy of 'Valencia' sweet orange trees under field conditions, with no irrigation system. Were evaluated three plants, whose planting rows were north-south oriented. The evaluations were performed during one day in each season of the year: summer, autumn, winter and spring. The values of water potential measured at predawn ranged from -0,31 MPa, in the day 12/10/05, to -1,1 MPa, in the day 08/30/05, however there was no significant difference between the east and west sides of the canopy. At the afternoon, leaves at the west side showed smaller (p<0,05) water potential than the ones at east position, with values varying between -0,95 (12/10/05) and -1,89 MPa (08/30/05). The largest air evaporative demand that is verified at afternoon induces to a larger water deficit in the west side of the canopy independent of the time of the year and, in consequence, larger SFD in well-watered plants under conditions of days completely sunny. Under water deficit conditions (low values of Ψl), the west side of the plants is more sensible to that condition, showing reduction of SFD.
