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Storage quality of lettuce leaves as affected by kinetin and abscisic acid Hemapat, Thosporn

Abstract

Some effects of post-harvest treatments of abscisic acid (ABA) and kinetin on the maintenance of quality and consumer appeal were studied on young lettuce plants. The treatments employed two concentrations of abscisic acid (1 and 5 ppm), one concentration of kinetin (20 ppm) and a combination of 5 ppm abscisic acid and 20 ppm kinetin. The plants were sprayed to the run-off point and placed in a storage chamber at 3±1°C with relative humidity close to 100%. After 6 weeks of storage all lettuce including untreated controls were in good condition. The chemical treatments did not have any distinct effect on the quality of lettuce as evaluated by a panel of observers for visual quality rating. The 20 ppm kinetin retarded chlorophyll degradation when compared to the control or the ABA-only treatments. Considering chlorophylls A and B separately, the kinetin-treated plants showed a significantly higher chlorophyll A content than other treatments, including the control. The differences in chlorophyll B content followed the same trend but only approached the 5% level of significance. ABA in the 5 ppm + 20 ppm kinetin treatment had a mild antagonistic activity to kinetin, and hence reduced the effect of kinetin on both chlorophyll A and B. Measurement of chlorophyll contents and adjustment to the original fresh weight before the samples were put in storage, provided a common basis to make comparisons for the study of chlorophyll degradation as functions of storage time and chemical treatment. Means of chlorophyll contents reported on this basis showed a trend of degradation from the 5th week to the 7th week. Temperature at 3±1°C and high relative humidity in the storage appear to be favourable for keeping lettuce. Hygenic preparation of the storage chamber also resulted in disease-free product even at the end of 7 weeks in storage.

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