Secondary thickening in dicotyledonous stem is controlled by the

Secondary thickening in dicotyledonous stem is controlled by the cambium. The cambium is a type of meristem, which is a specialized tissue that is responsible for the growth and development of plants. The cambium is located between the xylem and phloem tissues in the stem, and it is responsible for the production of new xylem and phloem cells during secondary growth. As the cambium produces new xylem and phloem cells, the stem increases in diameter, resulting in secondary thickening. The pericycle is a layer of cells in the root that is responsible for the initiation of lateral roots, but it is not involved in secondary thickening in the stem.