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Abstract : |
To investigate the effects of low temperature on the physiological and biochemical processes, we held two crisphead lettuce (Lactuca sativa L.) cultivars أƒآ¢أ‚€أ‚ثœShizuka` and أƒآ¢أ‚€أ‚ثœCisco` at 5أƒâ€ڑأ‚آ°C for 10 days. Minimum weight loss and lower respiration rate along with a higher hue angle value were recorded from both cultivars. However, cultivar أƒآ¢أ‚€أ‚ثœCisco` showed higher relative weight loss, respiration rate and accumulation of ammonia compared to that of أƒآ¢أ‚€أ‚ثœShizuka`. Except in the leaf portion of أƒآ¢أ‚€أ‚ثœShizuka`, glutamine synthetase (GS, 6.3.1.2) activity did not change significantly. The accumulation of ammonia was supposed to be below the critical level to repress GS activity. However, the highest amount of ammonia content was found at the end of the storage period in all cases. Amination activity of glutamate dehydrogenase (GDH, 1.4.1.2) decreased by day 4 and slightly increased thereafter while the deamination activity did not show any significant change. Overall, GDH-amination activity was remarkably higher than GDH-deamination activity and the leaf portion showed higher GDH-amination activity while the midrib portion showed higher GDH-deamination activity. Between the two cultivars, أƒآ¢أ‚€أ‚ثœCisco` could have a shorter shelf life than أƒآ¢أ‚€أ‚ثœShizuka`. The results suggested that although the visual quality of lettuce was maintained at low temperature, some physio-biochemical changes occurred in this period., |
