Abstract
This experiment was undertaken to clarify the mechanism of dry juice sac development histologically and physiologically with Hyuganatsu (Citrus tamurana Hort. ex Tanaka).
1. Dry juice sacs began to appear near the central axis and then spread along the side membranes of the segment. It was found that the epidermal cells of affected vesicles were twisted and dried out, showing comparatively high permeability of membranes to water.
2. It was shown by the test of injecting a given volume of pigment solution into the center of the segment of mature fruit on the tree that the pigment solution moving around seeds from the injected site was translocated into axial bundles through seed bundles in segments with healthy vesicles, while in segments with severe dry juice sacs, it did not move into axial bundles but remained at the injected site.
3. Respiration and ethylene production of vesicles developing fruit rapidly increased from mid May to mid June, although they had markedly been suppressed until early May. They rapidly increased again during the early developmental stage of dry juice sacs, being followed by a decline with the advance of the disorder. Comparing with peel tissue of healthy fruit, respiration rate per unit of fresh weight was higher in that of disordered one. It appeared that more ethylene was produced in vesicles along the side membranes than in those of the other portions of the segments in mature fruit. The diffusion rate of ethylene was markedly increased in segments with healthy vesicles by incising the connecting wall of side membranes along the axial bundle of mature fruit.
4. During the development of dry juice sacs specific gravity of fruit and total soluble solids, total sugars and citric acid contents of fruit with dry juice sacs became much lower than for healthy fruits. In particular, fruit showing the reduction of citric acid content to about 1 percent of the juice was apt to produce dry juice sacs.
