PREDICTION OF DORMANCY PERIOD AND STORAGE LIFE IN BULB ONIONS

摘要

The effect of various temperatures (4, 8, 14, 20, 25, and 30°C) on dormancy characteristics and storage span were investigated in two cultivars of onions namely, Texas Early Grano (TEG) and Dorcheh. There was a linear relationship between rate of sprout growth and temperature (P<0.05). As temperature increased from 4 to 14°C, rate of sprouting increased. Further increased in temperature to 30°C causes a decrease in the rate of sprouting. From the regression equations, the base, optimum and maximum temperature for breaking dormancy and sprouting in cv. TEG were -2.15, 14.85 and 33.76°C, respectively. Cardinal temperatures also for cv. Dorcheh were -1.78, 15.34 and 31.79°C. The thermal time requirement for breaking dormancy was 398.8°Cd in cv. TEG and 799.5°Cd in cv. Dorcheh. There was a significant difference in thermal times required for breaking dormancy between two cultivars (P<0.001). Plotting percentage of visible sprouting against thermal times resulted in a linear relation in both cultivars (r{sup}2=0.98 and P<0.01). Thermal times (θ) requirement for 100 percent visible sprouting was 2264°Cd in cv. TEG and 2662°Cd in cv. Dorcheh.