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 Fig. 6.2-2.
Longitudinal section of shoot tip of coleus (Coleus). Two types of
meristem are present here, based on the types of tissues they produce. The
outermost layer of cells across the top of the apical meristem and leaf
primordium is a meristem called the protoderm: its cells are still dividing and
their progeny cells will develop into epidermis cells. The two cells bulging
from the protoderm of the leaf primordium will develop into trichomes -- they
are trichome initials, and they can also be called trichome meristemoids.
Look carefully at the center of the shoot apical meristem, at the cells
just below the protoderm. They are slightly larger, slightly more irregular than
the cells on the periphery of the meristem; as these central cells divide and
enlarge, they push surrounding cells into the peripheral region. This push
causes the cells to move from one part of the meristem to a different part,
basically these central cells produce the cells for the rest of the meristem.
Such a region is called a promeristem. The promeristem in this species is not
particularly easy to see.
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