Growth regulators can improve the quality and productivity of fruit trees. This study was conducted at the Palm Research Station in Bushehr Province for two consecutive years and aimed to evaluate the effects of pre-harvest spraying with growth regulators on the physicochemical properties of date palm (Phoenix dactylifera cv. ‘Shahabi’) fruits at halal and tamar stages. In the first year, the fruit bunches of these trees were sprayed at the kimri stage and in the second year at the kimri and hababouk + kimri stages with NAA (100 mg/L), GA3 (100 mg/L), KI (100 mg/L), SA (50 mg/L), Put (1.288 × 103 mg/L) and distilled water as a control. Foliar spraying of all the plant growth regulators on the bunches of date cultivar ‘Shahabi’ at the kimry stage did not have a significant effect on the parameters such as fruit length, diameter, weight and volume compared to the control, but foliar spraying with NAA and to some extent Put at the hababouk + kimry stage resulted in a significant increase in these parameters at the halal and tamar stages. Foliar spraying with all the growth regulators resulted in a significant increase in pulp weight at both the halal and tamar stages. At the flowering stage, bunch weight and yield percentage increased significantly after foliar spraying with Put, SA, GA3 and especially NAA compared to the control. Overall, the fruit drop percentage was significantly higher with all the growth regulators as foliar spray at the hababouk + kimry stage compared to foliar spray at the kimry stage. Foliar spraying at the kimri stage significantly reduced the number of fruit drop, but foliar spraying with NAA, GA3 and SA at the hababook + kimri stage significantly increased the number of fruit drop compared to the control. Foliar spraying with all the PGRs at the kimri and hababook + kimri stages resulted in a significant decrease in the percentage of TSS as well as the percentage of total carbohydrates compared to the control at the halal and tamar stages. Foliar spraying with all the PGRs at the kimri and hababook + kimri stages resulted in a significant increase in the percentage of TA at the halal stage compared to the control.
Addition of 100 mg/L NAA by injection increased bunch weight and improved fruit physical characteristics such as weight, length, diameter, size, pulp percentage and TSS in date palm cultivar ‘Kabkab’. However, grain weight, acidity percentage and non-reducing sugar content were not changed. Exogenous GA had no significant effect on pulp percentage at different stages of fruit development and NAA had the highest pulp percentage8.
Related studies have shown that when the IAA concentration reaches 150 mg/L, the fruit drop rate of both jujube varieties is significantly reduced. When the concentration is higher, the fruit drop rate increases. After applying these growth regulators, fruit weight, diameter and bunch weight increase by 11.
The Shahabi variety is a dwarf variety of dates and is highly resistant to small amounts of water. Also,
The fruit has a high storage capacity. Due to these characteristics, it is grown in large quantities in Bushehr province. But one of its disadvantages is that the fruit has little pulp and a large stone. Therefore, any efforts to improve the quantity and quality of the fruit, especially increasing the fruit size, weight and, ultimately, the yield, can increase the income of producers.
Therefore, the aim of this study was to improve the physical and chemical properties of date palm fruits using plant growth regulators and select the best option.
With the exception of Put, we prepared all of these solutions the day before foliar spraying and stored them in the refrigerator. In the study, Put solution was prepared on the day of foliar spraying. We applied the required growth regulator solution to the fruit clusters using the foliar spray method. Thus, after selecting the desired trees in the first year, three fruit clusters were selected from different sides of each tree at the kimry stage in May, the desired treatment was applied to the clusters, and they were labeled. In the second year, the importance of the problem required a change, and in that year four clusters were selected from each tree, two of which were at the hababuk stage in April and entered the kimry stage in May. Only two fruit clusters from each selected tree were at the kimry stage, and growth regulators were applied. A hand sprayer was used to apply the solution and stick the labels. For best results, spray the fruit clusters early in the morning. We randomly selected several fruit samples from each bunch at the halal stage in June and at the tamar stage in September and carried out the necessary measurements of the fruits to study the effects of different growth regulators on the physicochemical properties of the fruits of the Shahabi variety. The collection of plant material was carried out in accordance with the relevant institutional, national and international norms and laws, and permission was obtained to collect the plant material.
To measure the fruit volume at the halal and tamar stages, we randomly selected ten fruits from each cluster for each replicate corresponding to each treatment group and measured the total fruit volume after immersion in water and divided it by ten to obtain the average fruit volume.
To measure the percentage of pulp at the halal and tamar stages, we randomly selected 10 fruits from each bunch of each treatment group and measured their weight using an electronic scale. We then separated the pulp from the core, weighed each part separately, and divided the total value by 10 to obtain the average pulp weight. The pulp weight can be calculated using the following formula1,2.
To measure the moisture percentage at the halal and tamar stages, we weighed 100 g of fresh pulp from each bunch per replicate in each treatment group using an electronic scale and baked it in an oven at 70 °C for one month. Then, we weighed the dried sample and calculated the moisture percentage using the following formula:
To measure the fruit drop rate, we counted the number of fruits in 5 clusters and calculated the fruit drop rate using the following formula:
We removed all the fruit bunches from the treated palms and weighed them on a scale. Based on the number of bunches per tree and the distance between plantings, we were able to calculate the increase in yield.
The pH value of juice reflects its acidity or alkalinity at the halal and tamar stages. We randomly selected 10 fruits from each bunch in each experimental group and weighed 1 g of pulp. We added 9 ml of distilled water to the extraction solution and measured the pH of the fruit using a JENWAY 351018 pH meter.
Foliar spraying with all growth regulators at the kimry stage significantly reduced fruit drop compared to the control (Fig. 1). In addition, foliar spraying with NAA on the hababuk + kimry varieties significantly increased the fruit drop rate compared to the control group. The highest percentage of fruit drop (71.21%) was observed with foliar spraying with NAA at the hababuk + kimry stage, and the lowest percentage of fruit drop (19.00%) was observed with foliar spraying with GA3 at the kimry stage.
Among all treatments, the TSS content at the halal stage was significantly lower than that at the tamar stage. Foliar spraying with all PGRs at the kimri and hababuk + kimri stages resulted in decreased TSS content at the halal and tamar stages compared to the control (Fig. 2A).
Effect of foliar spraying with all growth regulators on chemical characteristics (A: TSS, B: TA, C: pH and D: total carbohydrates) at Khababuck and Kimry stages. Mean values following the same letters in each column are not significantly different at p < 0.05 (LSD test). Put putrescine, SA - salicylic acid (SA), NAA - naphthylacetic acid, KI - kinetin, GA3 - gibberellic acid.
At the halal stage, all growth regulators significantly increased the whole fruit TA, with no significant differences between them compared to the control group (Fig. 2B). During the tamar period, the TA content of foliar sprays was lowest in the kababuk + kimri period. However, no significant difference was found for any of the plant growth regulators, except for NAA foliar sprays in the kimri and kimri + kababuk periods and GA3 foliar sprays in the kababuk + kababuk period. At this stage, the highest TA (0.13%) was observed in response to NAA, SA, and GA3.
Our findings on the improvement of physical characteristics of fruits (length, diameter, weight, volume and pulp percentage) after the use of different growth regulators on jujube trees are consistent with the data of Hesami and Abdi8.
Post time: Mar-17-2025