All above ground parts of a plant - leaves, stem, flowers, and seeds - ultimately are derived from cells of a small tissue at the tip of the shoot. Biologists call this tissue the "apical meristem", and it contains totipotent stem cells that are active throughout the life of the plant. Unlike the stem cells of animals, which can only produce specific kinds of tissue after the animal is past its embryonic stage, plant stem cells remain their totipotency and, therefore plants can continue growing over many years, developing new organs.
But this ability comes at a price. If the number of meristematic stem cells increases too quickly, then there could be uncontrolled growth, similar to cancer. On the other hand, if the stem cell pool shrinks too quickly, the plant could have stunted growth. In order to stay alive and reproduce, the plant needs to find the right balance in the number of its stem cells. Two regulatory mechanisms were found to be important for this process. The first involves growth-promoting hormones like auxin and cytokinin, known already for more than half a century. The second involves genetic factors, which were discovered at the University of Tübingen, Germany about a decade ago. Here it was shown that a gene called WUSCHEL has a key influence on how many cells in the apical meristem actually stay stem cells. However, until now, it was unclear how hormones and regulatory
Contact: Dr. Jan Lohmann