Morphological and Physiological Changes during Fruit Growth and Maturation of Seven Melon Cultivars

Abstract

External color, length, diameter, fresh weight, C0 2 production, internal C 2 H A concentration, flesh firmness, soluble solids concentration (SSC), flesh color, and seed cavity diameter were measured during fruit growth and maturation of seven melon cultivars (Cucumis melo L., Inodorus Group, Naud. cv . `Amarelo', `Golden Beauty Casaba', `Honey Dew', `Honey Loupe', `Juan Canary', `Paceco', and `Santa Claus Casaba') of known age. There was no increase in C0 2 production either during ripening (e.g., loss of firmness and increased SSC) or with increasing C 2 H 4 levels in fruit from any of the seven cultivars. There was a significant decline in respiration only at the second sampling date, which ranged from 14 to 18 days after anthesis. Respiration measured 1 week later was substantially higher and was followed by a general decline. This post 14- to 18-day rise in respiration was not a climacteric since it occurred well in advance of other ripening characteristics, e.g., loss of firmness, increase in SSC, or rise in internal C 2 H 4 . The increase in internal C 2 H 4 . coincided with or followed attainment of full fruit size, while flesh softening and the rapid rise in SSC preceded the rise in internal C 2 H 4 , concentration. Respiration declined from 67 to 18 ml CO 2 /kg per hour by day 43 in all cultivars, except `Honey Dew' and `Honey Loupe'. Respiration in `Honey Loupe' remained above 23 ml CO 2 /kg per hour and showed a rise to 32 ml/kg per hour on day 53. Respiration in `Honey Dew' did not fall below 18 ml CO 2 /kg per hour until day 53. As with internal C 2 H 4 levels, there was no correlation between changes in and any marked change in the other signs of ripening that were measured.