Effects of Crop Load on Water Stress, Fruit Quality, Yield and Flower Bud Formation on Root-Restricted Wase Satsuma Mandarin Trees Grown Indoors

The effects of crop load on water stress, yeild, and fruit quality of 13-year-old rootrestricted satsuma mandarin (Citrus unshiu Marc. var. preaecox Tanaka) trees grown indoors were investigated. The trees were heated from early December to late May. The fruits were thinned to a leaf-to-fruit ratio of either 15 (L :F-15) or to 10 (L : F-10) in early April.1. Trees with L:F -5 had lighter crops of smaller frutis with higher Brix than had trees with L :F-10.2. As fruits ripened in June to July, soil water potential, pF, of L :F -15 plots nearly exceeded those in L :F -10 plbts. The leaf water potential was lower and early leaf abscission was greater on L :F -15 trees than on L :F -10 trees. Thus, satsuma mandarin trees with L :F-15 underwent a more severe water stress than did trees with L :F-10 trees.3. The total and reducing sugar contents in the bearing shoots at harvest were significantly higher in the L : F-15 treatment than shoots in the L: F-10 treatment, but there were no differences in the fine roots (< 2 mm diam.). However, no difference in the starch content was observed in shoots and fine roots between the two treatments.4. The number and length of shoots appearing after summer pruning in the L:F-10 and L : F-15 trees were nearly equal. In late October and late November, the starch contents of the new shoots were lower in the L :F -10 treatment than in the L : F -15 treatment. No difference existed in the number of flower buds between trees of the two treatments when they were forced in December of the second year.