Physiology of pre-harvest drop in Thompson navel orange (Citrus sinensis)
2012
Akhlaghi Amiri, N. | Arzani, K. | Barzegar, M. | Asadi Kanarshahi, A.
In some citrus cultivars, pre-harvest drop is one important reason for high losses in this important horticultural crop in Iran. Obtaining more information about abscission physiology may reduce or delay it with appropriate treatments. Therefore this experiment was conducted to investigate auxin, cellulase and polygalacturonase in the abscission zone of Thompson navel orange, and its relationship with fruit abscission. An experiment was performed in a randomized complete block design with 7 treatments: 1) Control; 2) 2,4-D; 3) 2,4-D + urea; 4) 2,4-D + ZnSO4; 5) 2,4-D + sucrose; 6) 2,4-D + GA3; and 7) GA3 + urea, and 4 replications. Results showed that the control had the highest abscission percent, the lowest auxin and the highest enzyme levels. Treatments 2, 3 and 4, significantly reduced abscission compare to the control. Auxin increased significantly in these treatments. Polygalacturonase levels in treatments 2 and 3 were significantly reduced. Abscission had a significant negative correlation with auxin and a significant positive correlation with hydrolytic enzymes. Therefore, treatments 2, 3 and 4, delayed reduction of auxin level, and decreased production or activation of hydrolytic enzymes and postponed breakdown of cell walls in the abscission zone, thus resulting in a significant reduction in pre harvest drop compare to the control.
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