Gibberellic Acid and Salicylic Acid Dual Application Improves Date Palm Fruit Growth by Regulating the Nutrient Acquisition, Amino Acid Profile, and Phytohormone Performance

Gibberellic acid (GA3) and salicylic acid (SA) are crucial phytohormones that support fruit development. The objective of this study was to investigate the mechanism of spraying 100 mg L−1 GA3 and 100 mg L−1 SA in improving the Phoenix dactylifera, cv. Zaghloul fruit yield and quality. The experiment was conducted in a randomized complete block design during two successive growing seasons and four treatments [control (distilled water spray), 100 mg L−1 GA3, 100 mg L−1 SA, and 100 mg L−1 GA3 + 100 mg L−1 SA] were sprayed at the Hababouk and Kimri stages of date palm “Zaghloul” cv. The findings revealed that the GA3 and/or SA applications are necessary for improving the growth and development of “Zaghloul” fruit, which were associated with an increase in the content of dry matter, crude fiber, ash, total soluble solids, total soluble sugars, carbohydrate, protein, and essential nutrients. Moreover, compared with the control treatment, GA3 and/or SA exogenous treatments improved the activity of peroxidase and catalase, as well as the content of amino acids and phytohormones, while decreasing the content of moisture, total acidity, total phenol, and tannins. The results provide evidence that using GA3 in conjunction with SA has the greatest effect on improving “Zaghloul” fruit yield by up regulating the sugar accumulation, amino acid profile, nutrient acquisition, antioxidant capacity, and phytohormone performance. Consequently, combining GA3 with SA can be an effective strategy for enhancing fruit yield and quality.