Influence of Short-term Application of Abscisic Acid in Nutrient Solution on Growth and Drought Tolerance of Tomato Seedlings

Abstract

This study was conducted to evaluate influence of short-term application of abscisic acid (ABA) in nutrient solution on growth and drought tolerance of tomato seedlings. The treatments included four ABA concentrations (0.5, 1, 2, 3mg·L -1 ) and control (non-treatment) were applied to the nutrient solution in a hydroponic system. On the 5 th and 10 th day after growing in the nutrient solution containing ABA, seedlings were transferred to -5 bars of PEG-8000 in a growth chamber to induce water stress. Except for stem diameter and fresh and dry weight of root, there were no statistical differences in other growth parameters among control, 0.5 and 1mg·L -1 of ABA treatments. Seedlings growths were strongly inhibited in nutrient solution containing 2 and 3mg·L -1 of ABA. The root growth such as fresh and dry weigh of root, total root surface area, and average root diameter was slightly enhanced in 1mg·L -1 of ABA treatment. The elevation of ABA concentrations in nutrient solution resulted in the decrease in transpiration rate and increase in stomatal diffusive resistance and leaf temperature of tomato seedlings. The initiations of seedling wilting after treating in -5 bars of PEG were delayed from 10 hrs in control to 30 hrs in ABA applied treatments. Additionally, the high percentages of recovered seedlings were observed in 0.5 and 1mg·L -1 of ABA treatments after re-irrigation. Therefore, short-term application of 1mg·L -1 of ABA in the nutrient solution stimulated the root growth and drought tolerance of tomato seedlings by delaying the start time of wilting point and enhancing the recovery after re-irrigation.