effect of gibberellin concentrations and spraying time on cracking of pomegranate fruit (punica granatum l.) cv. “malas esfahan”

abstract fruit cracking of pomegranate is a phenomenon that is shown at most growing zones of the world. pomegranate cracking is the main obstacle for production and export, and have a lot of annual economic damage, the present study has been done about pomegranate trees. the purpose of this research is surveying the decreasing of pomegranate cracking and increasing the fruit quantities and qualifies characteristic by using of diverse concentrations of gibberellic acid that is sprayed at the different times. this experiment has been done at pomegranate orchard of isfahan center for research of agricultural science and natural resources. this study was conducted as a factorial experiment based on randomized complete block design in three replicates. experimental treatments including gibberellin sprayed with four concentrations of 0, 150, 300 and 450 mg/l, which was applied in three times, including full bloom, a month and two months after full bloom. gibberellin decreased cracking percentage compared to control. different stages of gibberellin application did not show any significant difference on cracking percentage. however, by increasing of concentrations and application close to 3rd stage, the cracking rate was decreased. in the first stage, all of used gibberellin concentrations were caused parthenocarpy, and the fruits didn't grow. the effect of gibberellin at different stages and concentrations was significant on the total weight and skin fresh weight. length, diameter, total acidity, size and volume of fruit were increased by increasing of gibberellin concentrations. the concentration of 450 mg/l showed the maximum effects on fruit quantities and qualities characteristics.