Open growth pattern
characterizes the growth of plants, which continues throughout their lifespan
but not uniformly throughout their body, as the growth is confined to certain
regions called meristem. Meristems are groups of cells that retain the ability
to divide by mitosis and produce daughter cells, which grow and form the rest
of the plant body.
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| Photomicrograph of root apical meristem |
There are three types of
meristem located at the stem and roots of plants: apical meristem, intercalary
meristem, and lateral meristem.
(a)
Apical Meristem: Responsible for Primary Growth
Apical meristems are
located at the root and shoot apex, and they are responsible for primary
growth, which gives rise to the primary plant body.
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| Photo-micrograph of shoot apical meristem |
(b)
Intercalary Meristem: Allow Growth in Length to Occur in Regions
Other Than Tips
Intercalary meristem is
located between regions of permanent tissue, such as the bases of grass leaves
or the nodes of many monocotyledons. They allow growth in length to occur in
regions other than tips and play an important role in the production of leaves
and flowers. These meristems are of temporary nature.
(c)
Lateral Meristem: Responsible for Secondary Growth
Lateral meristems are
laterally situated in older parts of dicot plants and gymnosperms, such as cork
cambium and vascular cambium. They are responsible for secondary growth.
Lateral meristem may be determinate, such as leaves, flowers, and fruits that
grow to a certain size and then stop or indeterminate, such as vegetative roots
and stems that grow continually by meristems that replenish themselves,
remaining youthful.
In conclusion, open growth
is the pattern of growth in plants, and the process of growth is confined to
certain regions called meristem. There are three types of meristem in plants,
namely apical meristem, intercalary meristem, and lateral meristem, which are
responsible for primary and secondary growth in different parts of the plant
body.
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