Apical meristem is a group of meristematic (educational) cells organized in a growth center, which occupies a terminal position in the stem and ensures the formation of all organs and primary tissues of the shoot .
The word "apical" comes from lat. apex - “top”, in this case - the top of the shoot, in which the growth cone is located.
Content
Location
Apical meristems are located at the top of the shoots (main and lateral) and at the tip of all young roots . Such an arrangement of meristems is determined already in the initial phases of ontogenesis . A fertilized egg during division forms a pre-embryo (proembryo), consisting of embryonic (meristematic cells). With the differentiation of the proembryo body, the groups of meristematic cells that form the apical meristems are localized at the tip of the primary root and at the top of the primary kidney. The apical meristems cause the growth of shoots and roots in length (height), their branching. Each lateral shoot and root also has an apical meristem.
Building
The upper part of the apical meristem is represented by initials (a single cell in horsetails and many ferns and a multicellular structure in seed plants ). The closest derivatives of the initial cells are often secreted into the protomeristem zone. Following it lie tissues that are already partially differentiated, but still in the meristematic state, which are referred to as the partially determined primary meristem. Depending on the tissue systems it produces, the deterministic meristem includes the following cell complexes: tunic , which further forms the primary integumentary tissue (epidermis ) and part of the primary cortex , and the body , the cells of which gradually form a complex of conductive tissues (central cylinder); in the root - dermatogen , differentiating into the primary integumentary tissue ( rhizoderm ); perible - the future primary cortex; pleroma - the central cylinder. Thus, the future course of development of meristematic tissues is partially determined by their very placement in the shoot and root apex.
See also
- Proliferation
Literature
- Atlas on Plant Anatomy: Textbook. manual for universities / Bavtuto G. A., Eremin V. M., Zhigar M. P. .. - Mn. : Urajay, 2001 .-- 146 p. - (Textbook and textbook. Textbooks for universities). - ISBN 985-04-0317-9 .