Phytohormones in plant responses to boron deficiency and toxicity.

The article reviews the roles of phytohormones in plant responses to boron (B) deficiency and toxicity, focusing on how hormonal signaling mediates growth and developmental adaptations. Boron is essential for plant cell wall integrity, primarily through cross-linking rhamnogalacturonan-II, but has a narrow optimal range, with deficiency inhibiting root elongation and toxicity causing oxidative stress and leaf damage. Key hormones involved include auxin, which regulates root elongation under B deficiency via altered synthesis and transport; ethylene and jasmonic acid, which interact to inhibit root growth; cytokinin, which modulates cell division and differentiation; brassinosteroids, which influence root growth inhibition; salicylic acid, which enhances antioxidant defenses under B toxicity; and abscisic acid, which mediates stomatal closure to reduce B uptake and transport during toxicity. The review emphasizes the complex hormonal networks that regulate plant adaptation to B nutritional disorders and highlights the need for further research on B signaling mechanisms and hormone interactions to improve crop resilience and nutrient management.