CALCIUM RETARDS PHYSIOLOGICAL COLLAPSE AND SUBSEQUENT MICROBIAL DEGRADATION OF MUNG BEAN (Vigna radiata L. Wilczek) SPROUTS

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Abstract
Mung bean (Vigna radiata L. Wilczek) sprouts, when germinated in water with no added calcium, were prone to physiological collapse of the cell walls below the cotyledonary hook. Growth of the collapsing hypocotyls gradually decreased until it stopped completely as the collapsed area extended cross-sectionally. Scanning electron micrographs indicated that extensive microbial degradation of the collapsed area of the low-calcium hypocotyl ensued by day 4 of germination. In contrast, at the same stage of germination, bacteria were essentially absent on sprouts germinated with calcium added to the water either as CaCl2, or Ca(NO3)2. Even by day 7 the calcium-treated hypocotyls remained intact and without any visual microbial degradation although bacteria were present on the surface of the seedlings. It is concluded that mung bean sprouts are very sensitive to physiological collapse with subsequent microbial degradation of the hypocotyl especially at temperatures above 20 °C. Therefore, it is recommended that water used for germinating the sprouts has sufficient calcium added (e.g. 5 × 10−3 M CaCl2) to maintain the integrity of the hypocotyls and reduce the microbial flora on the sprouts.Key words: Hypocotyl, growth, deterioration, mineral supplement