Meristematic tissues
A major difference between plants and animals is
that plant growth is not limited to an embryonic or
juvenile period. Instead, growth occurs throughout
the plant’s life process known as indeterminate
growth. At any given time, a typical plant has
embryonic, developing, and mature organs.
Except for dormant periods, most plants grow
continuously. In contrast, most animals and some
plant organs – such as leaves, thorns, and flowers
- undergo determinate growth; that is, they stop
growing after reaching a certain size.
Plants are capable of indeterminate growth because
they have perpetually undifferentiated tissues
called meristems that divide when conditions
permit, leading to new cells that elongate.
According to their origin and development,
meristems are classified as promeristem,
primary meristem and secondary meristem.
The meristem may also be classified according
to their position in the plant body as apical,
intercalary and lateral.
Apical meristems, located at the tips of roots and
shoots and in axillary buds of shoots, provide
additional cells that enable growth in length, a
process known as primary growth.
b) Sclereids:- They are highly Thickened dead
lignified sclerenchyma cells with very narrow
cavities. Different type of sclerids are
i) Brachysclereids / Stone cells:- They are short,
unbranched, isodiametric with branched pits.
eg:-girth of guava, sapota, peas etc.