INTERACTION OF ROOT CONFINEMENT AND FRUITING IN PEACH

Fruiting and nonfruiting 'Washington' peach trees were grown in 2.4- ( small) or 9 liter (large) containers to determine the influence of roo t confinement and fruiting on vegetative growth, fruit growth and qual ity, CO2 assimilation (A), and carbohydrate content. Shoot length, fru it diameter, A, and leaf carbohydrates were measured weekly. Thirteen weeks after transplanting, trees were divided into roots, shoots, leav es, and fruit for dry weight measurement. The dry weight of all organs except fruit was reduced by root confinement, and only the weight of stems formed the previous season was not reduced by fruiting. Fruit dr y weight was 30.0 g/tree for large- and small-container treatments, ca using the yield efficiency (g fruit/g total dry wt) to be 50 % higher for confined trees. Fruit red color, weight, and diameter were unaffec ted by root confinement, but higher flesh firmness and a more green gr ound color of the fruit surface from root-confined trees suggested tha t confinement delayed maturity. Vegetative growth was not reduced by l ack of nonstructural carbohydrates in confined trees. A was reduced by root confinement on only the first of 11 measurement dates, whereas f ruiting increased A on 5 of 8 measurement dates before fruit harvest. Fruit removal reduced A by 23 % and 31 % for nonconfined and confined trees, respectively, within 48 h of harvest. Leaf starch, sucrose, sor bitol, and total carbohydrate levels were negatively correlated with A when data were pooled, but inconsistent responses of A to carbohydrat e content indicated that factors other than feedback inhibition were a lso responsible for the reduction in A on nonfruited trees. We hypothe sized that a physiological signal originating in roots of confined tre es reduced vegetative growth without reducing fruit growth.