Pendimethalin is a cell division and cell elongation inhibitor. It acts by disrupting microtubules, the strands in the cell that act in the process of cell division (mitosis).
Microtubules also control the growth of cell walls. When the microtubules are absent or no longer fulfil their function, there is no control of cell wall growth. The so-called cellulose-microfibrils (cell wall building blocks) are no longer interwoven in parallel but are scattered at random instead. This leads to a loss of strength and elasticity of the cell wall, giant cells are often formed and tissue swelling results. The result is a cessation of elongation and growth.
Pendimethalin belongs to the dinitroaniline chemical group, classified as HRAC Group K1.