Effects of foliar melatonin application on the flowering and fruit set of pomegranate (Punica granatum L. Wonderful)
A naturally occurring compound, melatonin (N-acetyl-5-methoxytryptamine), is mainly released by the pineal gland at night and has long been known to cure insomnia and adjust sleep-wake cycles in people. Recently, horticultural scientists suggested that melatonin may be used to regulate plant root and shoot growth, stimulate seed germination and delay leaf senescence. However, the impacts of melatonin on plants have not been studied well, and very little information is available about the impacts of melatonin on flowering. Therefore, the present study was conducted to determine the impacts of foliar melatonin application (5 ppm, twice) on the number of flowers, flower sex, fruit set, flower drop, fruit drop and fruit position. For this reason, 18 pomegranate (Punica granatum L. Wonderful) trees were selected from a 5-year-old orchard and randomly divided into two groups. One group was sprayed with distilled water as a control, and the other was treated with melatonin (5 ppm). Applications were performed twice with an electrical mist sprayer as a foliar application. The first application was performed just before flowering, and the second was applied 21 days later. Results of current work demonstrated that the melatonin treatment significantly increases the number and percentage of fruit set. The average number of fruit set was recorded to be 37.5 in the control group, which increased to 48.6 at the melatonin-treated group. Therefore, flower drop was less at the melatonin-treated trees (77.0%) than at the non-treated trees (81.1%). This difference was not because of the male and non-viable hermaphrodite flowers (NVHF) but because of the viable hermaphrodite flowers (VHF). The average number of dropped VHF was 27.1 at the melatonin-treated trees and 34.9 in the control groups. Consequently, current results showed that the melatonin treatment has no significant influence on the number of flowers, flower sex, flower and fruit position but significantly reduces the fruit fall and VHF drop, which increases the fruit set.
Usanmaz, S., Aşkın, M.A. and Kahramanoğlu, İ. (2022). Effects of foliar melatonin application on the flowering and fruit set of pomegranate (Punica granatum L. Wonderful). Acta Hortic. 1349, 63-72
number of flowers, fruit set, fruit drop, viable hermaphrodite flowers, non-viable hermaphrodite flowers, male flowers