EFFECT OF WATER DEFICIENCY ON YIELD OF WHEAT

The objective of this work was to evaluate the effects of water defici ts on some parameters associated with yield, as well as defining criti cal water deficiency periods and their intensities in relation to whea t yield. The experiment was set up in a greenhouse in pots, under 18 d egrees C and 65% humidity. Water deficiency levels of -1.0, -2.0 and - 3.0 MPa were applied when plants reached the phenological stages of th e fourth leaf, flag leaf, anthesis and milking stage. The plants were rehydrated as soon as the stress levels were reached. Flag leaf stage was the most sensitive to water deficiency, resulting in the greatest yield reduction, followed by anthesis and fourth leaf stages. A water deficit of -2.0 MPa, applied at anthesis, reduced leaf area without af fecting the grain yield. The water deficit imposed at flag leaf stage was associated with reductions in spike weight, thousand grain weight, and number of grains per spike, as well as with late tillering. Grain yield reduction in wheat occurred only when the water deficiency leve l exceeded -2.0 MPa, affecting mainly the number of seeds per spike.