Involved in the control of root hair tip growth by promoting microtubule depolymerization and limiting the accumulation of endoplasmic microtubules. In vitro; binds to polymerized actin through ARM repeats; and to polymerized tubulin through N-terminal motor domain. {ECO:0000269|PubMed:17957256; ECO:0000269|PubMed:17971038}.