Relationship with Dissolved Oxygen Content of Floodwater and Flooding Tolerance of Mango (Mangifera indica) Tree

Abstract

In this study, we investigated the effect of dissolved oxygen in water on the survival of mango trees, as well as the distribution of carbohydrates in the trunk of trees submerged up to 5 cm above the graft union. The trees were assigned to three treatments: no flooding (control), waterlogging plus aeration (dissolved oxygen content: 6.35 mg/L), and waterlogging (dissolved oxygen content: 2.63 mg/L). Decreased dissolved oxygen in flooded water accelerated leaf wilting. Tissue of the scion bark collapsed regardless of dissolved oxygen concentration. Total sugars and non-reducing sugars in the scion trunk were increased by the flooding treatment regardless of dissolved oxygen concentration. This suggests that submergence may restrict the migration of non-reducing sugars, such as translocation sugar, at the graft union. There was no significant difference in the amount of reducing sugars among the treatments; however, the degree of leaf wilting was positively correlated with the amount of reducing sugars or the ratio of reducing sugars to non-reducing sugars in the scion wood. This suggests that the amount of reducing sugars increases with the progress of tree damage. Although tree death itself appears to be related to collapse of the scion bark and limitation of sugar migration through graft union, decrease in dissolved oxygen may accelerate the progress of tree damage, exacerbate damage to the scion, and hasten death.