The inner L3 layer is called the corpus. Cells in the L1 and L2 layers divide in a sideways fashion, which keeps these layers distinct, root apical meristem pdf the L3 layer divides in a more random fashion. Meristematic cells give rise to various organs of the plant and keep the plant growing. SAM and RAM cells divide rapidly and are considered indeterminate, in that they do not possess any defined end status.
In general, differentiated plant cells cannot divide or produce cells of a different type. Therefore, cell division in the meristem is required to provide new cells for expansion and differentiation of tissues and initiation of new organs, providing the basic structure of the plant body. Furthermore, the cells are small and protoplasm fills the cell completely. Maintenance of the cells requires a balance between two antagonistic processes: organ initiation and stem cell population renewal.
These differentiate into three kinds of primary meristems. The primary meristems in turn produce the two secondary meristem types. These secondary meristems are also known as lateral meristems because they are involved in lateral growth. At the meristem summit, there is a small group of slowly dividing cells, which is commonly called the central zone. Cells of this zone have a stem cell function and are essential for meristem maintenance.
The proliferation and growth rates at the meristem summit usually differ considerably from those at the periphery. It is also helps In the growth of the plant. Meristems also are induced in the roots of legumes such as soybean, Lotus japonicus, pea, and Medicago truncatula after infection with soil bacteria commonly called Rhizobium. The number of layers varies according to plant type. In general the outermost layer is called the tunica while the innermost layers are the corpus.
In monocots, the tunica determine the physical characteristics of the leaf edge and margin. In dicots, layer two of the corpus determine the characteristics of the edge of the leaf. The source of all above-ground organs. Cells at the shoot apical meristem summit serve as stem cells to the surrounding peripheral region, where they proliferate rapidly and are incorporated into differentiating leaf or flower primordia. The shoot apical meristem is the site of most of the embryogenesis in flowering plants.
Primordia of leaves, sepals, petals, stamens and ovaries are initiated here at the rate of one every time interval, called a plastochron. It is where the first indications that flower development has been evoked are manifested. The four distinct zones mentioned above are maintained by a complex signalling pathway. CLV1 has been shown to interact with several cytoplasmic proteins that are most likely involved in downstream signalling. Unlike the shoot apical meristem, the root apical meristem produces cells in two dimensions.
Intercalary meristems are capable of cell division, and they allow for rapid growth and regrowth of many monocots. When plants begin the developmental process known as flowering, the shoot apical meristem is transformed into an inflorescence meristem, which goes on to produce the floral meristem, which produces the sepals, petals, stamens, and carpels of the flower. In contrast to vegetative apical meristems and some exflorescence meristems, floral meristems cannot continue to grow indefinitely. Their future growth is limited to the flower with a particular size and form.