温州ミカンの着果負担に関する研究 (第4報)

Abstract

To clarify the effect of fruit load on the matter economy of satsuma mandarin trees, net production (ΔPn), dry matter loss by death and removal (ΔL), respiration loss (ΔR) and gross production (ΔPg) were surveyed in separate periods from April, 1972 to February, 1973 using bearing (4 fruits per plant) and non-bearing 3-year-old‘Miyagawa-wase’trees. Fruit load was regulated by hand thinning on July 15.1) From April 5 to May 31 (from sprouting to arrested current shoot elongation): ΔPg per plant in this period (57 days) was 41.0g, and ΔR accounted for 74 per cent of that. New organs grew vigorously accounting for 150 per cent of ΔPn. By contrast, old organs lost considerable weight.2) From June 1 to July 14 (from arrested current shoot elongation to fruit thinning): ΔPg in this period (44 days) was 48.1 g, and ΔR accounted for 60 per cent of that. Fruits and old organs initiated their rapid growth with retarded current shoot elongation.3) From July 15 to September 6 (from fruit thinning to rapid fruit growth): In the bearing trees, ΔPg in this period (54 days) was 90.7g, of which ΔR accounted for 54 per cent. Further, 37 per cent of ΔPn was distributed to their fruit. In the non-bearing trees, ΔPg was 127.7g, of which ΔR accounted for 52 per cent. This ΔR/ΔPg ratio was lowest among the non-bearing trees through the whole season. Each organ of the non-bearing trees grew more vigorously than that of the bearing trees.4) From September 7 to November 9 (from rapid fruit growth to harvest): In the bearing trees, ΔPg in this period (64 days) was 83.9g, of which ΔR accounted for 55 per cent. Further, 66 per cent of ΔPn was distributed to their fruit. In the non-bearing trees, ΔPg was 98.3g, of which ΔR accounted for 65 per cent. Further, 74 per cent of ΔPn was distributed to underground parts because of vigorous growth of root crowns and roots.5) From November 10, 1972 to January 11, 1973 (from harvest to arrested vegetative growth): In the bearing trees, ΔPg in this period (63 days) was 35.3g, of which ΔR accounted for 39 per cent. In the non-bearing trees, ΔPg was 28.1g, of which ΔR accounted for 76 per cent. This ΔR/ΔPg ratio was lowest among those of the bearing trees through the whole season. Since the bearing trees resumed their growth after harvest, their ΔPn was larger than that of the non-bearing trees.6) From January 12 to February 25 (arrested vegetative growth period): In this period (45 days) ΔPg was 7.7g in the bearing trees and 11.6g in the non-bearing trees. In each treatment trees showed little growth and ΔR was almost equivalent to ΔPg.7) Annual ΔPg of the bearing trees was 306.7g per plant, and 29%, 9%, 5%, 29% and 28% of it were distributed to leaves, stems, trunk, underground parts and fruits, respectively. Annual ΔPg of the non-bearing trees was 354.8g per plant, and 29%, 13%, 5%, 46% and 7% of it were distributed to leaves, stems, trunk, underground parts and fruits (until thinning), respectively. The bearing and non-bearing trees showed approximately the same annual ΔPn values; 131.0g and 132.4g per plant. Since annual ΔPn/ΔPg ratios of the bearing and non-bearing trees were 0.43 and 0.37, respectively, it was found that ΔPg of the bearing trees was utilized for ΔPn more efficiently than that of the non-bearing trees.