© 2005 Heron Publishing—Victoria, Canada
Regulated deficit irrigation and the recovery of water relations in pistachio trees
J. Guerrero (1), A. Moriana (1, 2), D. Pérez-López (1), J. F. Couceiro (1), N. Olmedilla (1) and M. C. Gijón (1)
1. CMA El Chaparrillo, Crta. de Porzuna Km 3.5, 13005 Ciudad Real, Spain / 2. Corresponding author (amoriana@jccm.es) / Received March 3, 2005; accepted May 28, 2005; published online October 3, 2005
Summary
Recovery of water status in water-stressed pistachio trees (Pistacia vera L. cv. Kerman) was investigated by subjecting trees to regulated deficit irrigation (RDI) (60% of crop evapotranspiration
rate, ETc) during stages I and II of fruit development (FD) followed by full irrigation during FD stage III (kernel-filling). Trees
irrigated at 100% ETc throughout FD stages I, II and III served as controls. Water-stress severity was characterized by changes in soil water content
and midday stem water potential (Ψmd). Midday leaf conductance (g1) and trunk diameter variation (TDV) were also measured. In RDI trees, the lowest Ψmd value, –1.8 MPa, occurred at the end of the RDI period. The corresponding value for the control trees was around –1.1 MPa.
Although the RDI treatment affected gas exchange later than Ψmd, the greatest reductions in gas exchange (60% of control values) also appeared at the end of the RDI period. There were significant
differences in TDV between control and RDI trees at the end of the RDI period. Although plant water status recovered within
20 days of resuming irrigation, the TDV values indicated a longer period might be necessary for complete recovery. Recovery
of g1 was faster than that of Ψmd, although differences in TDV between control and RDI trees indicated that gas exchange recovered later than Ψmd. The slow recovery of pistachio trees during FD stage III from water stress imposed during FD stages I and II suggests that
irrigation should exceed 100% ETc during FD stage III or that more extensive irrigation should commence before the end of FD stage II.
Keywords:
leaf conductance, maximum daily shrinkage, Pistacia vera, plant water status, stem water potential, TDV, trunk growth rate.
