Drought-Hardening Improve Waterlogging Tolerance of Maize at Seedling Stage

This study aimed to investigate the stress tolerance of maize by exploring the changes in abscisic acid (ABA) concentration, biomass accumulation, and transpiration rate of maize exposed to drought and waterlogging stress; The experiment was conducted in a controlled greenhouse by setting up a total of 17 treatments of water stress, waterlogging stress, and drought stress followed by waterlogging. A completely randomized block design was employed; Waterlogging limited the formation of maize biomass more than that by water stress. Waterlogging alone (W) inhibited more strongly the growth of the aboveground part than of the underground part, causing a de-crease in the canopy-to-root ratio. However, the canopy-to-root ratio increased under waterlogging after drought. Under drought and waterlogging stress, the ABA concentrations of maize leaves and roots changed gradually, decreasing from the leaves to the root base, then middle root, and finally root tip. Early water stress had a greater effect on leaf ABA concentration than on root ABA concentration, and leaves were the most sensitive to drought stress. Root system was more sensitive to drought stress followed by waterlogging; Moderate controlled drought at the seedling stage can improve their resistance to subsequent waterlogging stress, but the subsequent water-logging stress should not last more than 7 days.