ROOT-GROWTH, WATER RELATIONS, ABSCISIC-ACID AND PROLINE LEVELS OF DROUGHT-RESISTANT AND DROUGHT-SENSITIVE MAIZE CULTIVARS IN RESPONSE TO WATER-STRESS

Two maize (Zea mays L.) cultivars, the one drought resistant (PNR473) and the other drought sensitive (SR52), were grown in a greenhouse under two watering treatments: a control treatment, in which plants were watered throughout, and a water stress treatment, in which plants were subjected to a period when watering was withheld. The response of growth and some physiological characteristics of the two cultivars were compared. The drought-resistant cultivar had a lower growth rate than the drought-sensitive cultivar in the control treatment, but had a higher growth rate and deeper rooting than the drought-sensitive cultivar in the water stress treatment. There were no differences between the cultivars in some physiological characteristics in the control treatment, but in the water stress treatment the drought-resistant cultivar had a higher transpiration rate and lower diffusive resistance during the onset of water stress, and higher relative water content and levels of abscisic acid and proline throughout the period of water stress.