Abstract:

The paper aims to clarify the dynamic characteristics of fruit morphology as well as carbohydrate content of wax gourd, and to provide a theoretical basis for its high quality and high yield cultivation. The large black wax gourd ‘Tiezhu No.2’ was used as the material in this study. The fruit appearance, pulp cell structure, content of carbohydrates, and the activities of enzymes like α-galactosidase were observed at fruit setting stage, young fruit stage, fruit enlargement stage and mature stage, respectively. During the development of wax gourd fruit, cell division mainly happened in the early stage (the first 15 days after flowering) and cell expansion dominated the late stage. The transverse and longitudinal diameters changed with the development of fruit and presented as “S” curves, and their spatial differences in the upper, middle and bottom parts of the fruit were observed. In the fruit enlargement stage, the transverse diameter of the middle part was significantly lower than that of the other parts, and was related to the difference of cell volume. The main carbohydrates in fruit were fructose and glucose, accounting for 51% and 48% of the total soluble sugars, respectively. With the development of fruit, the concentration of soluble total sugar continuously increased, and the activities of neutral invertase, sucrose phosphate synthase, and sucrose synthase in the decomposition direction also gradually increased. However, the activities of soluble acid invertase, cell wall insoluble invertase, and α-galactosidase decreased. The total activities of sucrose decomposition enzymes were greater than those of sucrose synthesis enzymes across all growth periods. Therefore, 20-25 days after flowering is the key period for the growth of middle transverse diameter, and 25-35 days after flowering is important for the accumulation of sugar substances in wax gourd fruit. To improve the shape quality and economic value of wax gourd, early fertilization and proper management should be highlighted, and timely harvest at around 35 days after flowering is recommended.

Key words: black wax gourd, fruit growth and development, pulp cells, soluble sugar, enzyme activity