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Simple tissues
are also referred to as ground tissues. They include the tissues
known as parenchyma, collenchyma, and sclerenchyma. Parenchyma
tissue is composed of parenchyma cells, which are found throughout
the plant. They are particularly abundant in the stems and roots.
The leaf cells that carry out photosynthesis are also parenchyma
cells. Unlike many other plant cells, parenchyma cells are alive
at maturity and retain the ability to divide. They perform many
functions. Some are specialized for photosynthesis, others for
storage, and still others for secretion and transport. An important
class of parenchyma cells makes growth tissues called meristem
and cambium. These tissues give rise to all other tissues in the
plant body.
Like parenchyma
cells, collenchyma cells are alive at maturity. They differ from
parenchyma cells in that they have thick cell walls. Collenchyma
tissue is most often found in the form of strands or cylinders
of cells in stems and leaves. The thick cell walls of collenchyma
cells provide support to these plant structures. The strands of
tissue in celery are collenchyma tissues.
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