施設栽培で根域制限を行ったワセウンシュウの着果量が樹体の水分ストレス,果実の品質, 収量ならびに花芽分化に及ほす影響

Abstract

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.