Agronomic and Photosynthetic Characteristics of Different Maize Hybrids in Response to Water Deficit Stress at Different Phenological Stages

The aim of present study was to evaluate the effects of drought stress on net photosynthesis rate (Pn), stomatal resistance, water use efficiency (WUE) and biomass (BM) of six maize (Zea mays L.) hybrids. Drought stress applied by withholding water supply at 4-5 leaf stage (S1, vegetative stage), anthesis (S2, reproductive stage), and dual stress condition (S3, combination of vegetative and reproductive stages). Results showed that all of the traits changed differently among hybrids under water stress but recovered close to initial values after re-watering. S3 affected leaf gas exchange and agronomic traits more severely than S1 and S2 treatments. Pn decreased due to imposed drought but more slowly in hybrids SC647 and SC704. In addition, SC700, SC704 and SC647 had the maximum BM and plant height. But, WUE decreased during the water stress period especially in hybrids SC260 and SC370 in which the decrease was remarkable. It can be concluded that SC704 and SC647 were the most tolerant and SC260 and SC370 were the least tolerant hybrids to water stress. The variation observed amongst the evaluated hybrids suggests the existence of valuable genetic resources for crop improvement in relation to drought tolerance.