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

Abstract

Onion is one of the most cultivated crops and its production is increasing worldwide. Proper handling and storage will add huge benefits to the supply of onion to meet the demand of consumers. For storage, it is important to understand onion physiology from the day it has been harvested from the field until it reaches the market. This review summarizes the scientific literature related to the physiology of the onion bulb with respect to growth regulators, temperature, and chemical controls. The biochemical changes that occur during dormancy break and sprouting have been discussed in detail. The three main environmental factors that can influence onions during storage are temperature, humidity and composition of the atmosphere in the storage area. Among these factors, temperature plays a paramount role in the physiology of onion during pre-and postharvest storage. Particular emphasis was given to plant growth A c c e p t e d M a n u s c r i p t 2 hormones (endogenous and exogenous) and their consequent effects with respect to dormancy, sprouting and biochemical changes that occur in onions.

Morphological Performance of Onion under Exogenous Treatments of GA3

“…Globally, onion (Allium cepa L.) is an important crop that needs proper agricultural management in order to achieve a great flavour and to increase the production in regard with the consumer's demand (Sharma et al, 2015). It is the main spice crop rather than vegetable and therapeutic in Bangladesh (BBS, 2015).…”

Effect of prolonged storage in controlled atmospheres on the conservation of the onion (Allium cepa L)quality

“…The optimum temperature for sprouting is around 15 °C, but this value changes from a cultivar to another (Komochi, 1990). Sprouting occurs when the leaf primordia which are formed on stored bulbs, develop green leaves instead of cataphylls, which is longer and finally protrude from the neck of the bulb (Sharma et al, 2016).…”

“…According to Sharma et al (2016) the end of the dormancy of onion happens when the first inner sprout appear in the bulbs, but commercial storage life and market value of the onion continue until there is visible sprout growth and rooting. In the present study the onions stored in CA did not reach to break their dormancy, since they issued no sprouts during the 7 months of storage.…”

“…Endogenous hormones control this phenomenon. It is variable depending on the cultivar and environmental factors, in particular the temperature, which can extend it or shorten it (Sharma et al, 2016). However, during storage, especially during long periods, losses of marketable bulbs are recorded by either sprouting, rooting, decay, weight-loss or phytopathological damage (González et al, 2005).…”

Effect of harvesting practices, lifting time, curing and irrigation on quercetin content in onion (Allium cepa L.) cultivars

“…Onion extracts and the isolated bioactive compounds from onion has wide range of biological effects including antioxidant, antiplatelet, antidiabetic, anticarcinogenic, antiasthmatic, antimicrobial, anti-inflammatory and antibiotic effects on human health (Griffiths et al, 2002;Sharma, et al, 2015). Onion comprises two important groups of phytochemicals; flavonoids and the alk(en)yl cysteine sulphoxides, that are proved to be have beneficial effects to human health.…”