Abstract:

Through the analysis of the nitrogen metabolism of leaves and the correlation between the nitrogen content and metabolic-related enzyme activities, and the determination of fruit quality and yield, the appropriate concentration of PCPA in the greenhouse cultivation of seedless watermelon was discussed, and some theoretical references on the application of PCPA in seedless watermelon cultivation was provided. Physiological indicators such as soluble protein, total nitrogen content, metabolic-related enzyme (GS, NR and GDH) activities, fruit quality and yield were measured in different treatments using PCPA solution of different mass concentrations (0, 10, 20, 40 mg/L) at beginning of flowering period, full flowering period and young fruit period of seedless watermelon. The results showed that: (1) with the increase of the concentration of PCPA, the change trend of soluble protein, total nitrogen content and GS, NR and GDH activity of the leaves first rise and then fall; when the concentration of PCPA was 20 mg/L, the promotion effect was the most obvious, soluble protein, total nitrogen content of leaves and GS, NR and GDH activity were all the highest, significantly higher than those of CK; when the concentration of PCPA was 40 mg/L, soluble protein, total nitrogen content and GS, NR and GDH activity of leaves were reduced rapidly, and the indicators were all significantly lower than those of 10 and 20 mg/L treatments; the correlation analysis of the indicators showed that there was a significant or extremely significant positive correlation between total nitrogen content and GS, NR and GDH activity of seedless watermelon leaves; (2) among all the treatments, 20 mg/L treatment had the highest fruit yield and soluble solids content, both significantly higher than those of CK. Therefore, the appropriate concentration of PCPA used in greenhouse cultivation of seedless watermelon could be 20 mg/L.

Key words: Seedless Watermelon, PCPA, Nitrogen Metabolism, Fruit Quality, Yield