ISHS Acta Horticulturae 343: Physiological Basis of Postharvest Technologies
INTERNAL ATMOSPHERE AND WATERY SCALES IN ONION BULBS (ALLIUM CEPA L.) |
| Author: | H. Hoftun |
| Abstract:
Watery scales is a physiological disorder in stored onion bulbs, and may lead to considerable losses during the storage period. To get knowledge about this disorder and its causes some experiments were carried out, measuring the internal CO2 and O2 content. Before the measurements the onion bulbs were treated in different ways to restrict the gas exchange between the interior of the bulbs and the external atmosphere. Blocking the neck of the bulbs caused a dramatic increase in internal CO2 and decrease in O2, indicating that the main gas exchange took place through the neck. Through the root plate some gas diffusion was found, but to a small degree. The outermost dry scales were nearly impermeable to gas exchange. When the outer or the center part of onions were covered with Vaseline after the bulbs were cut about 2 cm beneath the neck, differences in CO2 concentrations were observed, indicating restricted gas diffusion from scale to scale inside the bulbs. Watery scales were observed when CO2 was above 13% and O2 below 4% in the internal atmosphere. It is suggested that onions are more sensitive to high CO2 than to low O2. | |
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