Effect of Temperature on the Growth, Pyruvic Acid and Sugar Contents in Onion Bulbs
2009
Lee, E.J., Kyungpook National University, Daegu, Republic of Korea | Suh, J.K., Kyungpook National University, Daegu, Republic of Korea
Flavor potential in onions is genetically determined, but it can be modified by environment. The aim of this study was to investigate the effect of temperature (15, 20, 25, 30℃) on the sugar and pyruvic acid contents and growth of onion (Allium cepa L.) bulbs. There were no differences in the plant height according to temperature. The number of leaves was decreased as temperature increased. However bulb diameter, bulb weight and bulbing index (bulb/neck diameter) were increased as temperature increased. Therefore aerial part growth was better at 20 and 25℃ and subterranean growth was better at 25 and 30℃. At harvest, there was a significant difference in bulb characteristics. It showed better growth in bulb diameter and weight at 25℃. The growth of bulbs was better but bulb weight was decreased lower at 30℃ because of stress. The pyruvic acid content in onion bulb was the highest at 20℃, while total sugar content was the highest at 25℃. The pyruvic acid and sugar content per unit weight of the bulb were the highest at 20℃. Onion grown at 25℃ was the highest in sweetness but much lower in PA/TS rate. Sucrose content was increased as temperature increased but there was no effect on glucose and fructose contents. Therefore, strong sweet flavor should be obtained when onions are grown at 25℃ condition.
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