Answer:
Placenta are
soft cushion like tissues with which the ovules are attached to the innersurface
of ovary wall.
The arrangement of
ovules within the ovary is known as placentation. The placentations are of
different types, i.e., marginal, axile, parietal, basal and free central.
Marginal
Placentation In this placentation, the placenta forms a ridge along the ventral
suture of the ovary and the ovules are borne on this ridge forming two rows, as
in pea.
Axile
Placentation In this placentation, the ovules are borne on central axis and
themarginal of placenta grow in word and fuse, thus making a multilocular
ovary, as in Chinarose, tomato, etc.
Parietal
Placentation In this placentation, the ovules develop on the inner wall of the
ovaryor on peripheral part. Ovary is one chambered but it becomes two chambered
due to theformation of a false septum known as replam, e.g., mustard.
Free Central
Placentation In this type of placentation, the ovules are present on the
central axis of ovary and septa is absent so ovary is unilocular, as in Dianthus
and Primose.
Basal
Placentation In this placentation, the placenta develops at the base of ovary
and asingle ovule is attached to it, as in sunflower.
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