The expression of histone 2A in onion (Allium cepa) during the onset of dormancy, storage and emergence from dormancy

Abstract

The tissue-specific and developmental expression of histone 2A was studied in onion (Allium cepa ' Robusta '), using northern blots. Histone 2A expression was enriched in basal tissues, particularly in the inner, meristematically active parts of bulbs. The expression was assessed during a time course of bulb development, dormancy onset and post-harvest sprouting in field-grown material. During bulb development histone 2A expression in the inner bulb declined rapidly during bulb ripening, reaching a minimum with the onset of dormancy. During post-harvest storage, expression increased slowly, reaching a peak in the spring, coinciding with the first observed sprout emergence. It was concluded that in onion, as in other plant systems, histone 2A expression is linked to cell division and dormancy level, the peak in expression during post-harvest storage indicating the time of dormancy breakage. In cultivars where post-harvest sprouting occurred much earlier or much later than in ' Robusta ', this expression peak occurred at about the same time of year, regardless of sprouting time. It was concluded that differences in storage longevity between cultivars were not due to differing times of dormancy breakage. Factors controlling the rate of sprout emergence post-dormancy are likely to be major determinants of storage capacity.

Quantitative analysis of flavonoids, sugars, phenylalanine and tryptophan in onion scales during storage under ambient conditions

“…During the dormancy, which supposedly started near harvest and varies from several weeks to months depends on the various cultivars (Miedema 1994;Yasin and Bufler 2007), many physiological processes are slowed down, although not ceased (Pak et al 1995;Carter et al 1999;Yasin and Bufler 2007;Brewster 2008). After the dormancy breaking, onion bulbs enter the regrowth phase that is accompanied by gradually increasing metabolic activity.…”

Importance of growth hormones and temperature for physiological regulation of dormancy and sprouting in onions

“…The duration of dormancy varies from several weeks to months depending on the cultivar, and the methods used in the determination of dormancy and sprouting. (16)(17)(18)(19) According to Espen, (20) dormancy in onion bulbs is a physiological state that could be linked to the metabolic changes following the source-to-sink transition, when the bulbs are prepared to sprout. The metabolic activity in onion depends on the source to sink transition, the source (scales) is where the carbohydrates are produced and the sink (base plate) is where they are consumed during the sprouting in onion.…”

Preharvest application of exogenous abscisic acid (ABA) or an ABA analogue does not affect endogenous ABA concentration of onion bulbs

“…Furthermore, plants of Allium wakegi that received fluridone (an inhibitor of ABA biosynthesis) as an aqueous soil treatment had reduced amounts of ABA in all parts of the plant, and the application of 25 or 125 mM fluridone decreased the number of days to sprouting from 45 days to 29 and 15 days, respectively (Yamazaki et al 1999a). Cell division is not closely linked with dormancy (Carter et al 1999), so the control of cell elongation, rather than cell division, is important in suppression of sprout growth. There is evidence that ABA inhibits cell elongation (Karagiannis and Pappelis 1994), which provides further support for the hypothesis that increasing the concentration of ABA in the crop before storage or decreasing the rate of degradation of ABA during storage could prolong storage potential by suppressing sprout growth (Chope et al 2006).…”