Dual Effects of Ethylene on Potato Dormancy and Sprout Growth

Abstract

Dormant potato tubers (Solanum tuberosum L.) of two cultivars were treated with various concentrations of ethylene gas for various exposure periods. As has been shown by others, ethylene caused a rapid but transient increase in respiration rate, which appeared to be independent of any effects on dormancy. All concentrations tested caused accelerated sprouting, 2 microliters per liter being the most effective. Ethylene exerts a dual effect on potato tubers: it markedly shortens the duration of rest, but it inhibits elongation of the sprouts during extended treatment. Comparing these results with published work on seeds, bulbs, and corms suggests that ethylene must have a significant but as yet unexplained role in rest and dormancy. However, since the most effective ethylene treatment did not equal the response elicited by treatment with ethylene chlorhydrin, other factors must also contribute to termination of rest.The initiation of sprouting in potato tubers is accompanied by a variety of biochemical changes which are usually reflected in changes in hormonal concentration, respiration rate, and the onset of nucleic acid synthesis and cell division and enlargement (16, 21, 24-26, 30, 31). A number of reports have supported the hypothesis that the rest period in potato tubers is regulated by gibberellins and ABA (24,26,30). However, the significance of other hormones, particularly of ethylene, has not been investigated adequately.That ethylene is an endogenous growth hormone for plants and a potent growth regulator is well established (1,23), but its role in the dormancy of potatoes and other plant organs has remained unclear. The older works on potato present conflicting evidence (4, 5), and there has been little clarification in recent work. Terminating dormancy in freshly harvested potatoes is an important practical problem, to which much attention has been given, and many chemical treatments have been tried (5,22). Rosa (28) was first to try ethylene; concentrations of 10, 200, and 1000 ,ull were applied for 28 days giving substantial increases in the stand obtained 1 month after planting. On the other hand, Denny (8, 9) tried ethylene, propylene, and acetylene at 1000 and 10,000 ,lll for 4 and 7 days and found them to be ineffective. In studies by Vacha and Harvey (32), ethylene treatments with 1000 ,ul/l at 20 C for 6 days gave 'This investigation was supported in part by North Atlantic Treaty Organization Research Grant 541 to L.R.2 On leave from Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. earlier sprouting and faster growth with some potato cultivars. Rosa (29) reported further tests with ethylene, using treatments of 455 and 2500 ,ul/l for 2, 3, or 4 weeks at 22 C; the 2-and 3-week treatments inhibited sprouting, whereas a 4-week treatment promoted sprouting (no difference between the concentrations was observed). In a better planned experiment with 800 ,1/1, ethylene accelerated emergence, especially in the shorter treatments. Another experiment with 500 1ul/l g...

Involvement of Ethylene in Potato Microtuber Dormancy

“…Subsequent studies identified a number of bioactive compounds in the volatile fraction, including benzothiazole, diphenylamine, and 1,4-and 1,6-dimethylnaphthalene (Meigh et al, 1973). Although ethylene was also identified as a component of the volatile fraction, its involvement in volatile-induced sprout growth inhibition was discounted because of its very low concentration in the total volatile fraction and its relatively poor bioactivity (Burton and Meigh, 1971;Rylski et al, 1974). Given the low rates of ethylene evolution and the ephemeral nature of the ethylene requirement, it is likely that without the use of the in vitro tuberization system and the specific inhibitors of ethylene action, the role of endogenous ethylene in potato tuber dormancy regulation would have again escaped detection.…”

“…Depending on the concentration and duration of exposure, exogenous ethylene can either hasten or delay tuber sprouting. Relatively shortterm (less than 3 d) exposure to ethylene results in the premature termination of tuber endodormancy, whereas long-term or continuous exposure to similar concentrations of ethylene inhibits subsequent sprout growth (Rylski et al, 1974). Temporary treatment with exogenous ethylene has also been reported to stimulate the sprouting of partially dormant tubers (Alam et al, 1994).…”

Regulation of potato tuber sprouting

“…Conflicting data have been published concerning its role during later stages of dormancy and sprouting as summarised by Suttle (2004bSuttle ( , 2007. In brief, exogenous application could either shorten or delay the dormancy period depending on the duration of treatment and the concentration applied (Rylski et al 1974;Prange et al 1998). Previously, Suttle (2009) reported that neither ethylene application nor stimulation of endogenous biosynthesis was effective in bud break or sprout growth.…”

Encapsulated calcium carbide enhances production and postharvest performance of potato (Solarium tuberosum) tubers

“…maximum tuber sprouting percentage was observed and it may be because eCC broke the dormancy of tubers and also reduced the production of growth inhibiting hormone abscisic acid (AbA) (el-Antably et al 1967;Alam et al 1994). it has been reported that short-term ethylene treatment can prematurely terminate tuber dormancy whereas continuous treatment results in delay in sprout growth inhibition (Rylski et al 1974). Similarly, treatment with ethylene releasing agents has been reported to either hasten or delay sprouting (Cvikrova et al 1994).…”