Effects of grafting on the morphology, physiology, and aerenchyma of balsam pear aboveground under waterlogging stress

The effects of grafting on the morphology, physiology, and aerenchyma of balsam pear aboveground under waterlogging stress were studied using a two-factor randomized block design. At 8 and 16 days, the degree of reduction of grafted balsam pear was lower than those of self-rooted balsam pear, although the height and leaf number of self-rooted and grafted balsam pears were remarkably reduced under waterlogging stress. Compared with self-rooted balsam pear, grafting considerably decreased the malondialdehyde content of balsam pear leaves but substantially increased the activities of antioxidant enzymes (superoxide dismutase, peroxidase, and catalase) and the contents of osmosis-regulating substances (soluble sugar, soluble protein, and proline) in the leaves of balsam pear under waterlogging stress at 4, 8, and 16 days. The stem of grafted balsam pear formed aerenchyma (pith cavity) at 0 days, whereas the stem of self-rooted balsam pear formed aerenchyma at 4 days. The aerenchyma of the stem formed by grafted balsam pear was more developed than that formed by the self-rooted balsam pear under waterlogging stress. The petiole of self-rooted and grafted balsam pears formed aerenchyma at 16 days, and the aerenchyma of grafted balsam pear was more developed than that of self-rooted balsam pear. These results indicated that grafting improved the antioxidant and osmotic regulation ability of balsam pear and enhanced the tolerance of balsam pear to waterlogging stress by enlarging the pith cavity of the stem and petiole of balsam pear.