Regulation of Bud Rest in Tubers of Potato, Solanum tuberosum L

Abstract

The rest period of the potato tuber was studied in relation to certain biochemical changes that are induced by gibberellic acid (GA3). The concentration of reducing sugars in excised plugs with buds treated with 10-M GA3 decreased in the first 4 hours after treatment and then rapidly increased up to 70 hours. The pattern in control buds was similar, but the changes occurred more slowly. The response to GAs is temperature-dependent and is not limited to any particular tissue of the tuber. The concentration of reducing sugars in excised buds increased proportionally to the log of the concentration of GA3 in a range from 10-8 to 10-4 M.At 10-3 M, GA3 slightly inhibited production of reducing (1,3,9,13,29,35,38,40). Application of gibberellic acid promotes sprouting of intact tubers during tuber development or after they are harvested as marketable (23,36,38 the level of enzymes associated with carbohydrate metabolism (4,19,25,32). There is mounting evidence that the hormone can induce synthesis of several hydrolytic enzymes (6,14,20,49,50). Working with Avena fatua, Simpson and Naylor (44) noted that the activity of maltase was higher in imbibed nondormant seeds than in imbibed dormant seeds. Gibberellin A3 caused an increase in maltase in dormant seeds, with a resultant increase in sugar production. Moreover, whereas excised nondormant embryos would grow on a sugar-amino acid medium, dormant embryos would grow on this medium only if GA3 was present (45). Thus in A. fatua, GA3 appears to have dual functions-to induce in the aleurone layers synthesis of enzymes that hydrolyze carbohydrate reserves and to induce in the embryo enzymes that utilize the resulting substrates. Development of cell wall invertase in tissue slices of Helianthus tuberosa in response to GA3 was observed by Edelman and Hall (10, 11) and Bacon, MacDonald, and Knight (2). Palmer (34) reported similar results with root slices of Beta vulgaris L.The expectation that GA3 would promote protein synthesis in potato buds was heightened by the observation that GA3 accelerates synthesis of RNA and DNA in excised buds from resting potatoes (39,41,49). We have shown (7) that reducing sugar content of potato buds increased shortly after excision, and the increase was accelerated by treatment with the hormone. It was therefore of interest to explore certain biochemical responses that occur in potato buds shortly after excision and treatment with GA3. MATERIALS AND METHODSPLANT MATERIALS White Rose potatoes were harvested 100 to 120 days after planting at which time they were in deep rest. The tubers were washed by hand and placed in the dark at 200. They were used within 3 days after harvest and were cooled to 00 hr before an experiment was begun; thereafter all procedures associated with preparation of plugs were at this temperature. In most experiments plugs with an apical bud (eye) were excised with a potato "deeyer" (internal diameter 0.8 cm) and cut to a length of 0.5 cm (35). In some experiments, 0.2 cm x 0.2 cm plugs with a bud were used. Such...

Comparative analysis of abscisic acid content and starch degradation during storage of tubers harvested from different potato varieties

“…However, from this highly specialised system it is not possible to deduce similarities to other tissue such as potato tubers. Clegg & Rappaport (1970) did not find a significant increase in either amylase activity following GA3-treatment of potato tubers. Furthermore, there are contrary results whether starch degradation in potato tubers is mainly amylolytic or phosphorolytic (Morrell & ap Rees, 1986;Davies & Ross, 1987).…”

The physiology of growth and tuber yield

“…The gibberellins and abscisic acid appear to act independently on the synthesis of nucleic acids rather than, say, abscisic acid inhibiting gibberellin synthesis. Increasing concentrations of gibberellins also promote the breakdown of starch to reducing sugars, but these do not appear to have any direct effect on the release of buds from dormancy (Clegg and Rappaport, 1970).…”

The Role of Cytokinin and Gibberellin in Potato Tuber Sprouting

“…In potato tuber, dormancy could be broken by the application of GAs which is reported by Hemberg (1985); Coleman (1987); Burton (1989); and Fernie and Willmitzer (2001). GAs may terminate dormancy by activating the synthesis of DNA and RNA (Clegg and Rapport, 1970;Burton, 1989;Arteca, 1996) and by decreasing the duration of the cells in the G 1 and S phases (Robberts, 1988). According to Francis and Sorrell (2001), GAs may affect the Cdc 2 kinase level at the G 2 -M checkpoint of the cell cycle and GAs may increase the rate at which cells are produced.…”

“…Transport takes place mainly in the phloem of the plants and can be both up and downward (Kefeli, 1978). GAs are generally considered to be responsible for cell elongation, rather than cell division (Kefeli, 1978;Vivanco and Flores, 2000;Francis and Sorrell, 2001), but may also play a role in stimulating cell division in meristematic areas (Kefeli, 1978;Clegg and Rapport, 1970).…”