Determination of water potential on mango trees by pressure chamber.
Castro Neto M. T., Reinhardt D. H., Ledo C. A. da S.
Author Affiliation: Embrapa Mandioca e Fruticultura, CEP 44380-000 Cruz das Almas, BA, Brazil.
: 425-427
Abstract : Four-year-old mango trees, growing in sand soil and irrigated by micro-sprinklers, were subjected to several different soil water potentials by letting the soil to dry out, after it was irrigated to field capacity. Both sap water potential (phloem sap) and xylem water potential decreased with a decrease of soil water potential. However, xylem water potential followed more closely the decrease in soil water potential, suggesting that it could be a good indication of the plant water potential. The determination of water potential in mango trees, using a leaf petiole in a pressure chamber did not correctly express plant water potential. The main problem of the leaf petiole method is that when pressure is applied, exudation of the sap from the phloem masks the exudation of the watery sap from the xylem, thus misleading the reading point for the determination of water potential. The use of a small branch instead of a leaf petiole for the determination of plant water potential has been suggested to adequately relate plant water potential to soil water potential.