Effects of potassium and calcium on vegetative growth and mineral balance of apple ‎tree grafted on dwarfing rootstocks, under salinity stress

Soil salinity is one of the most important abiotic stress that by disrupting mineral balance, affects the growth and fertility of plants. In order to investigate the effects of calcium and potassium nutrition on increasing the apple trees tolerance to salinity stress, a factorial experiment with a completely randomized design was conducted in two years, in which six nutritional solutions were used to simulate different levels of salt stress conditions by several amounts of calcium, potassium, magnesium and sodium chloride. According to the results, trees grafted on MM111 showed the earliest and the most frequent symptoms of chlorosis and necrosis in both years, and the trees grafted on M9 rootstocks showed less symptoms than two other rootstocks during the both years. In both years of experiment, correlation between percentage of necrotized leaves, leaf loss and decreasing vegetative growth with leaves chloride content was higher than their correlation with leaf sodium content. Also, the results showed that in both years of experiment, the D nutritional solution (5 mM KNO3, 3.5 mM Ca (NO3)2, 3.57 mM MgSO4 & 6 mM NaCl), could suppress the symptoms of stress in the trees and maintained their growth. Trees grafted on M9 rootstocks, were healthier during the stress period, and also after this period they had higher survival and recovery ability than the two other rootstocks.