240 Fruit Removal Effects on Growth and Carbon Allocation in Young Citrus Trees

Abstract

Fruit were removed 8, 16, and 24 weeks after peak bloom from 3- and 4-year-old, `Hamlin' orange [Citrus sinensis (L.) Osbeck] trees on `Carrizo' citrange root-stock [C. sinensis (L.) Osbeck ×Poncirus trifoliata (L.) Raf.], planted as bare root or containerized trees, to determine if fruit removal enhanced vegetative growth. Bare-root trees had a greater stem diameter and tree height than containerized trees at planting and after years 3 and 4. Fruit of bare-root trees had lower fresh and dry weights, refixed less of their respiratory CO2 during development, and lost water less rapidly after harvest. In addition, fruit removal treatments did not increase growth of either bare-root or containerized trees relative to trees from which no fruit had been removed. In fact, tree diameters were slightly higher when fruit were not harvested. Carbon cost of fruit production may have been countered by other factors under field conditions, such as known enhancement of photosynthetic rates by fruit load and/or diurnal contributions by fruit to leaf water demands.