IAA was involved in phosphorus deficiency-induced cluster roots formation in Macadamia integrifolia

Phosphorus (P) deficiency induced the formation and development of cluster roots in macadamia, thereby stimulating P acquisition by enhancing root surface area and carboxylate exudation. However, how P deficiency regulates the formation of cluster roots in macadamia remains unclear. Sand culture experiments were conducted to investigate the role of auxin in formation cluster roots induced by P deficiency. Our results demonstrated that P deficiency significantly triggered the formation of cluster roots in macadamia, as evidenced by an increase in the number, carboxylates exudation and acid phosphatase activity. These differences might be attributed to the accumulation and distribution of IAA in cluster roots induced by P deficiency, as demonstrated by the positive effect of IAA application and inhibitory effect of NPA. Our results provide valuable insights into the mechanisms of cluster roots formation stimulated by P deficiency.