Response of growth, physiological characteristics and concentration of some mineral ‎nutrients of local grafted watermelon to oxygen deficiency stress in hydroponic ‎system

In order to evaluate the tolerance of grafted watermelon plants on pumpkin, to oxygen deficiency conditions, a factorial experiment was carried out in the form of a completely randomized design in 5-liter plastic buckets containing Hoagland and Arnon's nutrient solution. The first factor was the amount of aeration of the nutrient solution in four levels (control, reduced aeration, no aeration and nitrogen injection) and the second factor was grafting in two levels (no grafting and grafting). The evaluations were based on the concentration of nutrients in leaves, and vegetative and physiological indicators. The results showed that although by reducing the oxygen in the nutrient solution or injecting nitrogen into the nutrient solution, the growth characteristics of the plant such as plant height, stem diameter, shoot fresh and dry weight, and root fresh and dry weight decreased significantly, but grafted plants, except for the stem diameter, had significantly better growth characteristics than non-grafted plants in other mentioned traits. With the decrease in dissolved oxygen of nutrient solution, the amount of proline and soluble sugars in the shoots and roots of grafted and non-grafted plants increased, but the concentration of proline and soluble sugars in grafted plants was higher than that of non-grafted plants. Oxygen deficiency stress decreased the amount of total chlorophyll, carotenoids and nutritional elements potassium, calcium, magnesium and phosphorus in shoot and root, but the concentrations of proline, soluble sugars and elements were higher in grafted plants than non-grafted plants. In short, according to the results of this research, grafting watermelon on pumpkin rootstock increased the tolerance of watermelon plant to oxygen deficiency conditions.