Answer: After the wheat radicle extends out of the seed coat, the radicle develops into the main root, and the meristem cells of the root tip divide constantly, some of them supplement the root cap cells, and some of them are elongated and transformed into elongated cells. Meridian cells always protect a certain volume and have strong division ability; Elongation zone is a cell derived from primary meristem, which initially differentiates and gradually transits to mature tissue and becomes mature zone. Due to the continuous division of meristem cells and the continuous elongation of elongation cells, roots can grow. Shortly after the wheat radicle extends out of the seed coat, 3 ~ 5 adventitious roots are produced at the base of the hypocotyl of the wheat embryo, which are generally called seed roots together with the main roots. Later, many adventitious roots will be produced on the main stem and tillering nodes or coleoptile nodes at all levels of embryo formation. Adventitious roots all have the same root tips as main roots, they extend and grow in the same way, and the root system formed is fibrous root system.