Brassinosteroid and gibberellin signaling are required for Tomato internode elongation in response to low red: far-red light

In this study, we explore the dynamic interplay between the plant hormones gibberellins (GA), brassinosteroids (BR), and Indole-3-Acetic Acid (IAA) in their collective impact on plant shade avoidance elongation under varying light conditions. We focus particularly on low Red : Far-red (R:FR) light conditions achieved by supplementing the background light with FR. Our research delves into how these hormones individually and synergistically influence stem elongation in tomato plants. Through meticulous experimental modulations of GA, IAA, and BR, we demonstrate that GA and BR are sufficient but also necessary for inducing stem elongation under low R:FR light conditions. Intriguingly, while IAA alone shows limited effects, its combination with GA yields significant elongation, suggesting a nuanced hormonal balance. Furthermore, we unveil the complex interplay of these hormones under light with low R:FR, where the suppression of one hormone's effect can be compensated by the others. This study provides insights into the hormonal mechanisms governing plant adaptation to light, highlighting the intricate and adaptable nature of plant growth responses. Our findings have far-reaching implications for agricultural practices, offering potential strategies for optimizing plant growth and productivity in various lighting environments. ### Competing Interest Statement The authors have declared no competing interest.