EFFECTS OF CHILLING TEMPERATURES ON CELLULARITY AND ULTRASTRUCTURE OF HONEY DEW FRUITS

Abstract

Honey dew melon is a warm season crop and susceptible to chilling injury (CI). CI is a disorder due to membrane structure change and malfunction of cell metabolism. The CI symptom for most melon cultivars reported to be water-soaking of the rind, surface pitting, greying or browning, flesh softening and increased decay. In this paper, we present some findings of honey dew fruits under three constant temperatures for four weeks to understand further the relationship between CI symptoms and cellular and/or ultra-structural change. Honey dew melons of cultivar 'Tainong No.2' were picked on December 30 from a commercial melon greenhouse near Lanzhou, packed in paper cartons, and kept for up to 28 days at relative humidity of 80±3% and three constant temperatures (2, 5 and 8°C). For each temperature treatment, three replicates of 3 cartons with 12 fruits were used. The results showed that chilling temperatures induced flatted cells, decreased micro-fibrils, and disintegrated plasmalemma and nuclear envelop. Cell deformation caused by low temperature was the direct reason of fruit pitting (typical CI symptom on honey dew) and quality deterioration. But the mitochondria in honey dew cells showed stronger stability under chilling temperatures.