Figure 1.

Mitochondria, which are located at the subapical zone of the elongating root hair, possess a mechanism for cyanide detoxification based in the CAS-C1 protein. Cyanide action in the root hair elongation process is exerted in a step between the SCN1 action, which inhibits ROP proteins, and the RHD2 NADPH oxidase action, which is regulated by ROPs and is essential for ROS production, Ca²⁺ influx and, ultimately, polar root hair growth. Full lines: established relationships; dashed lines: proposed relationships.