INFLUENCE OF LIFTING TIME , DURATION AND SHADING PROCESSES ON PERIDERM THICKNESS AND RESPIRATION RATE

Abstract

Potato tubers Solatium tuberosum L. cv. Desire produced during the spring seasons of 2001 and 2002 , were stored in the Storage Unit , Dept. of Horticulture. Tubers were lifted for three times : Early morning , mid-day and in the evening , then tubers were stored either immediately after lifting or left for one , two , or three hours in the field under shade or without it. Results indicated that the lifting at morning significantly increased the thickness of periderm layer at the end of storage period to 71.38 and 63.78 im as compared with tubers that lifted in the mid-day in which periderm layer was reduced to 61.16 and 56.47 im for both seasons. Respiration rate was retarded in potato tubers lifted in both early morning and in evening time as compared with the mid-day time in which respiration rate was increased for both seasons. Tubers lifted and then left for one hour significantly increased the thickness of periderm layer to 67.83 and 61.68 i.m , but it was decreased to 62.58 and 56.11 xm for tubers lifted for three hours before storing. Tubers stored immediately after lifting reduced the respiration rate , while this rate was increased as the lifting time increased. Shading tubers significantly increased the periderm thickness to 68.35 and 61.58 (im as compared with the periderm thickness of unshaded tubers which were of 65.86 jim and 59.98 Jim for both seasons , respectively .