Responses of Different Physiological Indices for Maize (Zea mays) to Soil Water Availability

Knowledge of plant responses to soil water availability is essential for the development of efficient irrigation strategies. However, notably different results have been obtained in the past on the responses of various physiological indices for different plants to soil water availability. In this study, the responses of various plant processes to soil water availability were compared with data from pot and field plot experiments conducted on maize (Zea mays L.). Consistent results were obtained between pot and field plot experiments for the responses of various relative plant indices to changes in the fraction of available soil water (FASW). A threshold value, where the relative plant indices began to decrease with soil drying, and a lower water limit, where the decline of relative plant indices changed to a very slow rate, were found. Evaporative demand not only influenced the transpiration rate over a daily scale but also determined the difference in transpirational response to soil water availability among the transient, daily and seasonal time scales. At the seasonal scale, cumulative transpiration decreased linearly with soil drying, but the decrease of transpiration from FASW = 1 in response to water deficits did not affect dry weight until FASW = 0.75. On the other hand, the decrease in dry weight was comparable with plant height and leaf area. Therefore, the plant responses to soil water availability were notably different among various plant indices of maize and were influenced by the weather conditions.