XVI International Botanical Congess

Changes of indices meanings of dividing and labelled with 3H-thymidine cells situated in tissues of wheat root tip over the length of 30 mm were studied. The cells of stellar parenchyma, pericycle, endodermis and cortex were analysed. The lateral root initiation by pericycle cells occurs while general resumption of cells proliferative activity of studied tissues takes place. It was stated that cell proliferation behind meristem and elongation zones starts with process of DNA synthesis resumption in their nucleus. DNA synthesis in cell nucleus of stellar parenchyma, pericycle and endodermis resumes after stillness period. This process in nucleus of some root tissues cells is a preliminary and necessary condition of their division that initiates development of lateral root primordia afterwards.