Preliminary Study On Characteristics Of K～+ Channel In Different Salt Tolerant Genotypes In Malus

K+/Na+ selectivity mechanism under salt tolerance was studied in Malus Zumi and Malus baccata (L. ) Borkh. It showed that after Na+ treatment K+ inward currents were inhibited significantly. The decreation is 40% in Zumi and 60% in baccata (L.)borlsh. It indicated K+/Na+ selectivity of baccata(L.)borkh root cells under salt stress was more sensitive than Zumi. After Glu-K was replaced by Glu-Na in solution, the inward currents weren't detective when membrane potential was as high as 180mV. It proved K+ channels was not the main route of Na+ fluxes in cells.After Ca²⁺ was added into solution for Na+ treatment, the K+ currents increased, which indicated Ca²⁺ could weaken the inhibition of Na+ on K+. K+ channel was open again and Na+ inward currents were inhibited at the same time. Effects of Ca²⁺ on K+/Na+ selectivity of inward channels in Malus Zumi and Malus baccata(L.)borkh was different. When the concentration of Ca²⁺ was increased continuously, K+ currents were inhibited.When Mg²⁺-ATP (K+ channels activator) was added to cytoplasm, K+ currents had no obvious attenuation in 20 minutes. Under Na+ stress, K+ currents were not inhibited significantly. It showed K+ channels and K+/Na+ selectivity was controlled by ATP. TEA+ and EGTA (K+ channels blocker) could block K+ currents, thus K+/Na+ selectivity was decreased. The patch-clamping showed that pH could control K+ inward currents.