Plant water status indicators for detecting water stress in pomegranate trees

Abstract

Measurements obtained by the continuous monitoring of trunk diameter fluctuations were compared with discrete measurements of midday stem water potential (PSIstem) and midday leaf conductance (gl) in adult pomegranate trees (Punica granatum (L.) cv. Mollar de Elche). Control plants (T0) were irrigated daily above their crop water requirements in order to attain non-limiting soil water conditions, while T1 plants were subjected to water stress by depriving them of irrigation water for 34 days, after which time irrigation was restored and plant recovery was studied for 7 days. T1 plants showed a substantial degree of water stress, which developed slowly. Maximum daily trunk shrinkage (MDS) was identified to be the most suitable plant-based indicator for irrigation scheduling in adult pomegranate trees, because its signal:noise ((T1/T0):coefficient of variation) ratio was higher than that for PSIstem ((T1/T0):coefficient of variation) and gl ((T0/T1):coefficient of variation). MDS increased in response to water stress, but when the PSIstem fell below ¿1.67 MPa, the MDS values decreased.