Effect of gibberellic acid and urea on the growth of pineapple fruit (Ananas comosus (L.) Merr.)

Abstract

Effects of gibberellic acid (GA3) and urea on Queen pineapples (Ananas comosus (L.) Merr.) growth in the field were discussed in this study. Pineapples were sprayed with GA3 (at the concentration of 1, 5, 10, 20, 40, 60, 80 and 100 mg.L^-1) or urea (at the concentration of 1, 5, 10, 15, 20, 25 and 30 g.L^-1) on day 0 and day 3 at the beginning of growth period (50% dried flowers). Fruits were sampled every 15 days from day 0 to day 75 for assessment on fruit weight, fruit size, and fruit quality. Besides, fruits (which were sprayed with GA3 at the concentration of 40 mg.L^-1 or urea at the concentration of 15 g.L^-1) were sampled on the 15th day from the day which processed to determine the size of cells. The results showed that the treatments with four highest concentration of GA3 (40, 60, 80 and 100 mg.L^-1) or urea (15, 20, 25 and 30 g.L^-1) significantly increased fruit weights and fruit sizes. In addition, the treatments of GA3 in high concentration (40 - 100 mg.L^-1) stimulated the increase of sugar content and vitamin C content in the fruit flesh compared to the control. The treatments of urea at different concentrations did not alter the fruit quality index. Exogenous GA3 at the concentration of 40 mg.L^-1 or urea at the concentration of 15 g.L^-1 stimulated the increase of fruit weight without decreasing the fruit quality. In which, exogenous GA3 at concentration 40 mg.L^-1 increased the fruit weight by enlarging flesh cell.