Yozo Okazawa

Viability, DNA Synthesis and Cell Wall Regeneration on Potato Protoplasts

Potato (Solarium tuberosum L.) plants have been regenerated from intact mesophyll protoplasts (Shepard and Totten 1977; Gunn and Shepard 1981; Carlberg et al. 1983; Haberlach et al. 1985; Bajaj 1986), from axenic shoot cultures (Binding et al. 1978; Thomas 1981; Sree Ramulu et al. 1984) and from axenic shoots regenerated from tuber tissue cultures (Kikuta et al. 1984). These developments have been extended by the recovery of somatic hybrids of Solarium tuberosum and Solarium brevidens by protoplast fusion (Barsfy et al. 1984) and the transfer of resistance to potato leaf roll virus from Solarium brevidens into Solarium tuberosum by somatic fusion (Austin et al. 1985). Despite this progress, experimental manipulation of potato protoplasts is still an extraordinary technique. A major problem is the inefficiency of protoplast division under conventional culture conditions.

Viability And Development Of Potato Protoplast Culture

The culture and regeneration of potato protoplasts are the two crucial steps in the application of protoplast manipulation for crop improvement. Although there have been a few reports that succeeded in recovery of plants from protoplasts in Solanum tuberosum (1–4), sustaining high viability and consistent development of potato protoplast culture still remain elusive. The work described here deals with the development of potato protoplast culture, in relation to this, the changes in viability of protoplasts, cell-wall regeneration and DNA synthesis for sustainment of the first cell division.

Physiological and Morphological Studies on the Potato Plants. : Part16. Some contribution to the physiology of dormancy, with special reference to the interrelation between ascorbic acid, phosphorylase and phosphatase in the potato tuber during the rest period.

While many of the practical problems concerning dormancy in the potato tubber have been solved, the internal physiological factors that govern this state are little understood. One of the more obvious methods of approaching this basic problem is to determine what changes occur in the enzymatic activity. In the present investigation, with a desire to obtain some further understanding of the physiology of dormancy, particular attention was paid to the interrelation between ascorbic acid, phophorylase and phophatase in the potato tubers during the storage period. The experimental results obtained may be summarized as follows: 1). Generally speaking, the activities of phosphorylase and phophatase showed little variation during the rest period. On the other hand, the ascorbic acid contents (reduced- and oxidized-forms) in the tuber decreased gradually with the again of the tuber during this peiod. 2). After the termination of the rest period, concomitant with the increase of the reduced ascorbic acid content in the apical bud of the tuber, remrkable high activities of phosphorylase and of phophatase were recognized, except for the phosphorylase activity in the pith of the tuber. 3). When considering the physiological role of the ascorbic acid in the germination and the biochemical action of the ascorbic acid as the activator of phosphatase enzyme, these increases in the terminal bud noted above, may be intimately related to the termination of the dormancy of potato tubers.