FRUIT MATURITY AND CALCIUM AFFECT CHILLING REQUIREMENTS AND RIPENING OF DANJOU PEARS

'D'Anjou' pear (Pyrus communis L.) trees were sprayed with zero or 32. 3 mM CaCl2 during fruit development at 55, 86, 125, and 137 d from ful l bloom and harvested at 85% (immature), 100% (mature), and 110% (over mature) maturity stages. The fruit were stored in air at -1 degrees C for several periods to determine the effect of CaCl2 treatments on chi lling requirement to accomplish ripening during 11 d at 20 degrees C, Immature or mature unsprayed fruit required 55 d, while the overmature fruit required 40 d at -1 degrees C to gain the capacity to produce e thylene during ripening at 20 degrees C. Calcium sprays increased fles h firmness at harvest by 15 N, fruit Ca concentrations by an average o f 0.01 mg.g(-1), fresh mass basis, and the chilling requirements by at least 15 d, Unsprayed immature fruit contained more Ca than the spray ed mature or overmature fruit, but their chilling requirement was simi lar. These results suggest that high Ca concentrations may increase th e chilling requirement of 'd'Anjou' pears in a developmentally related manner.