Synergistic effect of indole‒3‒acetic acid and nitrogen on yield, sugar profile, and nitrogen utilization of salt-stressed sugar beet crop
Ahmed Shaaban, Hani Saber Saudy, Mohamed A. M. Eid, Sammar. F. Zahran, Ali A. A. Mekdad
Abstract
Abstract Purpose Salt stress often reduces plant efficiency in nutrient utilization, particularly nitrogen (N), leading to physiological disorders, primarily those related to phytohormones. Hence, the current study assessed the combined effect of indole-3-acetic acid (IAA) and N in inducing salt stress tolerance in sugar beet. Methods Using a split-plot in randomized complete block design replicated thrice, the effect of three IAA levels (0, 150, and 300 mg L − 1 , denoted IAA 0 , IAA 150 and IAA 300 , respectively) and three N fertilization rates (240, 290, and 340 kg N ha − 1 , abbreviated as N 240 , N 290 and N 340 , respectively) on sugar beet’s growth, nutritional status, and quality and sugar quality in saline soil was explored. Results Findings exhibited that IAA 300 × N 340 was the best combination for enhancing root diameter, leaf fresh weight, and leaf area index. Ionic homeostasis, expressed as the leaf K⁺/Na⁺ and Ca²⁺/Na⁺ ratios, reached its highest values with N 340 (1.21 and 0.51, respectively), exceeding those observed with N 240 and N 290 . The IAA 0 or IAA 150 × N 340 gave the highest juice sodium content (34.0 and 33.8 mmol kg⁻¹, respectively), while N 240 across all IAA treatments recorded the lowest ones. The IAA 300 × N 340 was the most effective practice for enhancing yields and N use efficiency in sugar beet, resulting in the highest root yield (97.6 t ha⁻¹), pure sugar yield (14.50 t ha⁻¹), and N use efficiency (0.342 kg root kg⁻¹ N), significantly outperforming other IAA × N interactions. Conclusion In conclusion, progressive increases in IAA and N caused the enhancements sugar beet growth, yield, and related quality, since IAA at 300 mg L − 1 plus N at 340 kg N ha − 1 had the favorable synergism in this respect.