Morphological and Physiological Responses of Maize Seedlings under Drought and Waterlogging

Waterlogging and drought are severe constrains that limit maize seedling growth in tropical and subtropical regions. It is significant to determine the differences in morphological and physiological responses of maize to drought and excess soil water, with a view toward better breeding and field management. In the present experiment, different levels of soil water availability were initiated at the one-leaf (V1) stage of two maize cultivars (Denghai9 and Yidan629): Control (CK), Severe Drought (SD), Light Drought (LD), Severe Waterlogging (SW), and Light Waterlogging (LW). The results indicated that waterlogging had more discernible impact on the seedling growth of both cultivars than drought stress. The Relative Growth Rate (RGR) of shoots and roots, along with root length, volume, and surface area were all markedly decreased in both cultivars under waterlogging stress. The malondialdehyde content increased significantly in roots and leaves under waterlogging treatment. In both cultivars, SuperOxide Dismutase (SOD) was mostly activated in roots and leaves at the three-leaf (V3) stage by waterlogging stress, while the Catalase (CAT) activity apparently increased under drought stress. The activity of Peroxidase (POD) distinctly enhanced in both cultivars under drought and waterlogging stress. Ascorbate Peroxidase (APX) showed constant activity with prolongation of waterlogging stress, and Glutathione Reductase (GR) activity notably increased in roots under waterlogging conditions at the six-leaf (V6) stage. We concluded that SOD, POD, APX, and GR were the most important antioxidant enzymes under waterlogging conditions, whereas CAT and POD appeared to play key roles under drought stress.