Maryam Goodarzian-Ghahfarokhi - Department of Agronomy and Plant Breeding, Campus of Agriculture and Natural Resources, Razi University, Kermanshah, Iran
Cyrus Mansouri-Far - Department of Agronomy and Plant Breeding, Campus of Agriculture and Natural Resources, Razi University, Kermanshah, Iran
Mohsen Saeidi - Department of Agronomy and Plant Breeding, Campus of Agriculture and Natural Resources, Razi University, Kermanshah, Iran
Majid Abdoli - Young Researchers and Elite Club, Zanjan Branch, Islamic Azad University, Zanjan, Iran
Mohammad Esmaeilpour-Jahromi - Faculty of Agricultural Science, Jahrom University, Jahrom, Iran

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 ۴-۵ leaf stage (S۱, vegetative stage), anthesis (S۲, reproductive stage), and dual stress condition (S۳, 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. S۳ affected leaf gas exchange and agronomic traits more severely than S۱ and S۲ treatments. Pn decreased due to imposed drought but more slowly in hybrids SC۶۴۷ and SC۷۰۴. In addition, SC۷۰۰, SC۷۰۴ and SC۶۴۷ had the maximum BM and plant height. But, WUE decreased during the water stress period especially in hybrids SC۲۶۰ and SC۳۷۰ in which the decrease was remarkable. It can be concluded that SC۷۰۴ and SC۶۴۷ were the most tolerant and SC۲۶۰ and SC۳۷۰ 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.

Dry weight, Drought, Gas exchange, Re-watering, Water Use Efficiency