Source–sink relationships in sweet cherry were altered by girdling limbs both above and below fruiting spurs. Spurs isolated by girdling both above and below had lower total fruit weight per spur and lower weight per fruit then those above or below girdles. Fruit number per spur was not altered, but soluble solids and fruit color were lower in fruits from isolated spurs than fruit from spurs either above or below girdles. Fruit on spurs above girdles were generally highest in soluble solids and fruit color. These factors indicate fruit on isolated spurs also were delayed in maturity. Spurs below girdles were unaffected by girdling. Girdling had no effect on spur leaf net photosynthesis, stomatal conductance, or fruit water loss rate. The results indicate that spur leaves alone do not have the capacity to support fruit growth in sweet cherry and must, therefore, be supplemented by photosynthates from other sources.
Received for publication 18 Nov. 1986. Scientific research paper no. 7625, College of Agriculture and Home Economics Research Center, Washington State Univ., Pullman, WA 99164. This research was supported by the Washington Tree Fruit Research Commission. We thank Guy Auld for the use of his orchard. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact.