الفهرس 
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Abstract
The present study was conducted during two successive seasons 2017 and 2018 on thirty uniforms in vigor Balady acid lime trees, grown in private orchard located at Derwa Village, Mallawi Distract Minia Governorate (280 km southern Cairo city) where the soil texture is sandy and well drained water since water table depth is not less than two meters. The chosen acid lime trees are 10 years and planted at 4 X 4 meters apart. Surface irrigation system using well water was adopted. Winter pruning was followed at the last week of December in both experimental seasons.
The experiment involved the following tenth treatments from gibberellic acid concentrations and frequencies. As follow the ten treatments were arranged:
• Control, 0.0 ppm gibberellic acid (trees sprayed with water).
• Spraying gibberellic acid at 10 ppm one time.
• Spraying gibberellic acid at 10 ppm two times.
• Spraying gibberellic acid at 10 ppm three times.
• Spraying gibberellic acid at 20 ppm one time.
• Spraying gibberellic acid at 20 ppm two times.
• Spraying gibberellic acid at 20 ppm three times.
• Spraying gibberellic acid at 30 ppm one time.
• Spraying gibberellic acid at 30 ppm two times.
• Spraying gibberellic acid at 30 ppm three times.
Each treatment was replicated three times, one tree per each. Triton B at 0.05% as a wetting agent was added to all spraying solutions.
The most important results obtained during the two experimental seasons could be summarized as follows:
1- Vegetative growth characteristics:
All studied vegetative growth characters. i.e. main shoot length (cm), number of leaves/shoot, number of new shoots/tree and leaf area (cm2) were gradually stimulated in response to spraying the Balady acid lime trees once, twice and three times with gibberellic acid at 10 to 30 ppm, compared with control treatment. The best results were obtained due to spraying gibberellic acid at higher concentration 30 ppm three times. However, non-significant differences were noted, neither between the two highest concentrations, nor between the two highest frequencies of application two and three times.
2- Leaf pigments contents:
Increasing gibberellic acid concentration from 10 ppm to 30 ppm and its frequencies from one to three times was associated with gradual promotion on chlorophylls a & b and total chlorophyll (mg/100g F.W.), without significant promotion occurred among the highest frequencies namely two and three times. Furthermore, significant differences on the total carotenoids (mg/100g F.W.) were observed with increasing gibberellic acid concentration from 10 ppm to 30 ppm and frequencies from one to three times. However, using gibberellic acid at concentration above 20 ppm and frequencies above twice failed significantly to show promotion on total carotenoids. In this respect the untreated trees produced the minimum values. These results were true during both seasons.
3- Leaf chemical contents:
A promotion effect was observed on the Balady acid
lime leaf contents of macro nutrients (N, P, K and Ca) as well as micro nutrients (Fe, Zn and Mn) in the leaves when the gibberellic acid used once, twice and three times at 10 to 30 ppm, over the check treatment. Spraying the trees with gibberellic acid at 20 or 30 ppm two or three times gave the maximum values. However, non-significant differences were recorded neither between the trees received gibberellic acid at 20 ppm and those received 30 ppm nor between the trees received two or three sprays yearly. Therefore, from economical point of view, spraying gibberellic acid at 20 ppm two times during growth season was improved to be very effective in this respect.
4- Yield/tree as well as fruit weight and fruit numbers/tree:
Increasing gibberellic acid concentration from 10 ppm to 30 ppm had no considerable promotion on the number of fruits per tree in the first season of this study. Contrary of fruit numbers, fruit weight was remarkably improved in the first season.
In the second experimental season, a remarkable promotion in fruit number per tree, fruit weight, and yield (kg) per tree were observed. from economical point of view, for improving yield/tree as well as fruit weight and fruit number/tree it was preferable to spray gibberellic acid two times at 20 ppm.
5- Fruit Physical properties:
There was an obvious enhancement on physical properties of Balady acid lime fruits due to spraying gibberellic acid at different concentrations and frequencies, over the check treatment. This was appeared in terms of increasing fruit height & diameter, fruit volume and juice%. Spraying gibberellic acid at the highest concentration three times present higher and significant fruit height. While, treating the Lime trees with gibberellic acid at 20 ppm three times gave the best fruit volume, during both experimental seasons.
6- fruit Chemical properties:
Increasing concentrations of gibberellic acid from 10 ppm to 30 ppm and frequencies of application from one to three times had considerable promotion on the fruit quality in terms of increasing T.S.S. % as well as vitamin C contents and decreasing total acidity %, rather than untreated trees. However, non-significant differences were observed neither between the two highest concentrations (20 ppm & 30 ppm) nor between the two highest frequencies (two and three times). For improving yield and fruit chemical properties of Balady acid lime trees and from economical point view, it was preferable to spraying gibberellic acid at 20 ppm three times yearly.
Conclusion
from the results showed in this study it is clear that gibberellic acid may play a beneficial role in enhancing Balady acid lime trees growth aspects in terms of main shoot lengths, number of leaves per shoot and leaf area. Furthermore, increasing gibberellic acid concentration caused remarkably stimulation in fruit number/tree as well as fruit weight that lead to a significant increases the yield (kg)/tree. The obtained data also revealed that increasing gibberellic acid frequencies of application was associated with improvement of physical and chemical properties of Balady acid lime trees fruits. It is strongly recommended to spray Balady acid lime trees grown under the experimental condition (Minia Governorate) and resembling conditions with gibberellic acid at 20 ppm three times yearly, in order to improve the growth and production of Balady acid lime trees.