Effects of carbon dioxide on the physiological disorders observed in onion bulbs during CA storage

Abstract

Onions (Allium cepa L.) stored for 162–3 or 224–6 days in CA containing 10% CO2 and 3 to 5% O2 at 1°C showed physiological disorders. The same disorder appeared in all onion bulbs stored in sealed polythene bags containing over 10% CO2. Microscopic study of the epidermis and parenchyma of fleshy scales have demonstrated a process of destruction in walls of the onion cells. Free cellulose micelles were found inside such preparations due to hydrolitic enzyme activity. Alterations of the ultra-structure of the mitochondria were also observed. A high free amino acid content was found in onion bulbs with this physiological disorder. Total animo acid content was higher in the internal than in the external scales of onion bulbs.