COMPARATIVE WATER STRESS STUDIES ON DROUGHT RESISTANT AND SUSCEPTIBLE CORN GROWN IN CHAMBER AND FIELD ENVIRONMENTS

Abstract

Drought resistant and drought susceptible corn plants were grown in both field and growth room environments in order to study differences in response to water stress attributable to their growth environments, including their prestress history.After 40–56 days of growth, field- and chamber-grown drought resistant and susceptible plants were placed in a growth cabinet for the drought stress experiments. There they underwent two stress cycles, during which time water was witheld. During the cycles, leaf water potential, transpiration, stomatal resistance and soil moisture content were monitored. The response differences due to water stress between the drought resistant and susceptible plants were first examined. Response differences due to their prestress growth environments were then considered.The responses of the field- and chamber-grown drought resistant plants to stress were found to be similar although there were differences in the absolute value of the responses measured. This was also true of the drought susceptible plants. The drought resistant plants were able to maintain their ability to extract water for a longer period of time than the susceptible plants. They maintained low stomatal resistance values for a large part of the drying cycle. The values of leaf water potential at which the stomatal resistances increased were lower than those of the drought susceptible plants. This enabled the drought resistant plants to extend their period of water utilization.During the drying cycles, the field-grown drought resistant and susceptible plants maintained low stomatal resistances and high transpiration rates for a longer period of time than their chamber counterparts. The values of leaf water potential at which stomatal resistance increased and transpiration decreased were lower than those of the chamber-grown plants, allowing the field-grown plants a slightly extended period of water utilization.The knowledge of prestress history of plants grown in different environments is shown to be of importance when comparative studies between field and controlled environments are undertaken. The similarity in response found between field- and chamber- grown plants is a useful factor as the chamber work with these particular cultivars is shown to be representative of field response at this location.Key words: Water stress, drought resistance, Zea mays L.