INFLUENCE OF PREHARVEST WATER-STRESS ON POSTHARVEST MOISTURE LOSS OF CARROTS (DAUCUS-CAROTA L.)

To understand the relationship between preharvest water stress and pos tharvest moisture loss, carrot cvs Eagle and Paramount were grown in m uck soil in 61 pots (eight carrots per pot) in a greenhouse at the Uni versity of British Columbia. The plants were watered to field capacity every second day for 5.5 months prior to receiving 100, 75, 50 and 25 % field capacity water stress treatments (for 4.5 weeks), henceforth r eferred to as low, medium, high and severe water stress respectively. Postharvest moisture loss of carrots stored at 13 degrees C and 32% re lative humidity was monitored every second day for three weeks. The pe rcent moisture loss was low in the low water stressed, and high in the severely water stressed carrots of both cultivars. Root crown diamete r, weight, and water and osmotic potentials decreased, whereas specifi c surface area and relative solute leakage increased with increasing p reharvest water stress. The results show that carrots adjust to water stress by lowering water and osmotic potentials. Root water potential, followed by relative solute leakage, were the variables which account ed for most of the variation in moisture loss. It is suggested that pr eharvest water stress lowers membrane integrity of carrot roots, and t his may enhance moisture loss during storage.