STRATEGIES FOR DROUGHT RESISTANCE IN LEAVES OF 2 ALMOND CULTIVARS

Potted plants of two cultivars of almond (Amygdalus communis L.), Rami llete and Garrigues, growing under field conditions were subjected to drought by withholding irrigation for 28 days. Stressed plants were re irrigated 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 wat er stress effect, reaching -0.80 MPa in Garrigues and -0.98 MPa in Ram illete at the end of the stress period. The reduction in midday leaf c onductance in plants under water stress could be related to the reduct ion in midday leaf water potential. The reductions in leaf conductance values were about 62% and 79% for Garrigues and Ramillete, respective ly. Garrigues exhibited osmotic adjustment during the eater part of th e Stress period and this was sufficient to maintain the leaf turgor. T he relationship between leaf conductance and turgor pressure at midday appeared to be nearly linear over the range of turgor pressure observ ed. Ramillete presented lower leaf water potential at turgor loss poin t than did Garrigues. Both cultivars presented high relative apoplasti c water contents. The increase in these parameter values by water stre ss effect observed in Ramillete could indicate changes in cell wall st ructure. After rewatering, most of the parameters studied recovered qu ickly, although leaf conductance was delayed.