BSC 314 Lecture Notes - Lecture 6: Monocotyledon, Cork Cambium, Vascular Cambium
26 Jun 2018
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Meristematic Tissues
Meristematic tissues, or simply meristems, are tissues in which the cells remain forever
young and divide actively throughout the life of the plant. When a meristematic cell
divides in two, the new cell that remains in the meristem is called an initial, the other
the derivative. As new cells are added by repeated mitotic divisions of the initial cells,
the derivatives are pushed farther away from the zone of active division. They stretch,
enlarge and differentiate into other types of tissues as they mature. Meristematic cells
are generally small and cuboidal with large nuclei, small vacuoles, and thin walls.
A plant has four kinds of meristems: the apical meristem and three kinds of
lateral—vascular cambium, cork cambium, and intercalary meristem.
Apical meristems
These are located at opposite ends of the plant axis in the tips of roots and shoots. Cell
divisions and subsequent cellular enlargement in these areas lengthen the above and
below ground parts of the plant. The meristems also influence the shapes of the mature
plants since the patterns for subsequent growth are laid down in the meristems.
Lateral meristems
Vascular cambium. Some plants grow in diameter by producing new tissues laterally
from a cylinder of tissue called the vascular cambium, which extends throughout the
length of the plant from the tips of the shoots to the tips of the roots. It is present in
allperennial and in some annual plants. Tissues produced by cell divisions of the
vascular cambium are secondary tissues.
Cork cambium. Cork cambia (singular: cambium), also called phellogens, are found in
the bark of roots and stems of woody plants where they produce cork cells. The cork
cambia originate just under the epidermis of the primary body and in some tree species
are long cylinders running parallel to the vascular cambium. In other species, more
discrete, disk-like cork cambia in the trunks produce flat plates of bark tissues that
break off in large scales as the tree ages.
Intercalary meristem. Grasses have intercalary meristems located along the stems
near the nodes. Cell divisions in this tissue push the stem upward. Grasses and other
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Document Summary
Meristematic tissues, or simply meristems, are tissues in which the cells remain forever young and divide actively throughout the life of the plant. When a meristematic cell divides in two, the new cell that remains in the meristem is called an initial, the other the derivative. As new cells are added by repeated mitotic divisions of the initial cells, the derivatives are pushed farther away from the zone of active division. They stretch, enlarge and differentiate into other types of tissues as they mature. Meristematic cells are generally small and cuboidal with large nuclei, small vacuoles, and thin walls. A plant has four kinds of meristems: the apical meristem and three kinds of lateral vascular cambium, cork cambium, and intercalary meristem. These are located at opposite ends of the plant axis in the tips of roots and shoots. Cell divisions and subsequent cellular enlargement in these areas lengthen the above and below ground parts of the plant.
