Strategies for drought resistance in leaves of two almond cultivars

Abstract

Potted plants of two cultivars of almond ( Amygdalus communis L.), Ramillete and Garrigues, growing under field conditions were subjected to drought by withholding irrigation for 28 days. Stressed plants were reirrigated and the recovery was studied for 8 days. Control plants were drip irrigated daily maintaining the soil matric potential at about −30 kPa. Predawn leaf water potential declined progressively due to water stress effect, reaching −0.80 MPa in Garrigues and −0.98 MPa in Ramillete at the end of the stress period. The reduction in midday leaf conductance in plants under water stress could be related to the reduction in midday leaf water potential. The reductions in leaf conductance values were about 62% and 79% for Garrigues and Ramillete, respectively. Garrigues exhibited osmotic adjustment during the greater part of the stress period and this was sufficient to maintain the leaf turgor. The relationship between leaf conductance and turgor pressure at midday appeared to be nearly linear over the range of turgor pressure observed. Ramillete presented lower leaf water potential at turgor loss point than did Garrigues. Both cultivars presented high relative apoplastic water contents. The increase in these parameter values by water stress effect observed in Ramillete could indicate changes in cell wall structure. After rewatering, most of the parameters studied recovered quickly, although leaf conductance was delayed.