The Effect of IBA on the Ca2+ Absorption and Ca2+-ATPase Activity and Their Ultracytochemical Localization in Apple Roots
The uptake rate of Ca2+ and Ca2+-ATPase ultracytochemical localization were studied using Malus hupenensis Rehd seedlings and pot-cultured two-year-old apple trees (‘Starkrimson’/Malus hupenensis Rehd), after treatment with IBA. The results showed, IBA increased activity of roots and Ca2+-ATPase and rate of Ca2+ uptake. But Ca2+ uptake rates were inhibited by 2,4-DNP, the metabolic inhibitor, and the inhibition degree was higher under low Ca2+ concentrations (0 ～0.5 mmol/L) than high Ca2+ concentrations (0.5～5 mmol/L). The Km and Imax and the ratio (Imax/Km) all increased, and the inhibition degrees were higher in excised root than intact roots after roots were treated with IBA. The Imax and a (Imax/Km) increased but the Km after spraying IBA on leaves. 2,4-DNP inhibited the effects of IBA on Ca2+ absorption. Ca2+-ATPase was located on the cytoplasmic membrane and the vacuolar membrane. The activity of Ca2+-ATPase on the cytoplasmic membrane was increased significantly after treating by IBA.