EFFECT OF NITROGEN SUPPLY ON LEAF MINERAL-COMPOSITION OF APPLE-TREES UNDER SALINE CONDITIONS

The effect of N nutrition on the salt tolerance of apple cultivar 'Gol den Delicious' grafted either on M9 or M26 was evaluated in a sand cul ture system during 1989-1991. Three levels (4, 8 and 12 mM NO3-) of ni trogen were imposed. The growth medium was salinized with 30 mM NaCl o r Na2SO4. Leaf N and Ca2+ concentrations significantly increased with raising solution N level up to 8 mM, while the concentrations of K+, N a+, Cl-, and SO42- decreased. Leaves from trees on M9 accumulated much less K+, Na+, Cl- and SO42-, but more N and Ca2+ than those from tree s on M26. Trees stressed with Na2SO4 showed higher Na+, but lower Ca2 concentration than those treated with NaCl.