PLANT WATER STATUS AND FRUIT-QUALITY IN BRAEBURN APPLES

Five-year-old 'Braeburn' apple trees (Malus domestica Borkh.) on MM.106 rootstock were studied to determine plant and fruit quality responses to reduced plant water status late in the season. Trees were irrigated or not irrigated. Those not irrigated developed reduced xylem water potential and stomatal conductance from 110 and 132 days after full bloom (DAFB), respectively. However, they showed no reduction in photosynthetic rates. Fruit were harvested at stage 1 (S1), starting 167 DAFB, or stage 2 (S2), starting 180 DAFB. At S1, fruit had higher soluble solids concentrations, enhanced red skin pigmentation, and a tendency for higher sorbitol concentrations. Total soluble sugar concentrations at final harvest showed no difference between treatments, but fruit from the nonirrigated trees showed earlier sugar accumulation during the season. Such fruit also had reduced Ca+2 concentrations at S1 and S2 relative to those on plants that were irrigated. No incidence of any disorder was found in fruit from either treatment at harvest or after 12 weeks of 0C storage.