Stress-Triggered Long-Distance Communication Leads to Phenotypic Plasticity: The Case of the Early Root Protoxylem Maturation Induced by Leaf Wounding in Arabidopsis

Root architecture and xylem phenotypic plasticity influence crop productivity by affecting water and nutrient uptake, especially under those environmental stress, which limit water supply or imply excessive water losses. Xylem maturation depends on coordinated events of cell wall lignification and developmental programmed cell death (PCD), which could both be triggered by developmental- and/or stress-driven hydrogen peroxide (H₂O₂) production. Here, the effect of wounding of the cotyledonary leaf on root protoxylem maturation was explored in Arabidopsis thaliana by analysis under Laser Scanning Confocal Microscope (LSCM). Leaf wounding induced early root protoxylem maturation within 3 days from the injury, as after this time protoxylem position was found closer to the tip. The effect of leaf wounding on protoxylem maturation was independent from root growth or meristem size, that did not change after wounding. A strong H₂O₂ accumulation was detected in root protoxylem 6 h after leaf wounding. Furthermore, the H₂O₂ trap N,N¹-dimethylthiourea (DMTU) reversed wound-induced early protoxylem maturation, confirming the need for H₂O₂ production in this signaling pathway.