question_answer 54)

    The arrangement of ovules within the ovary is known as placenta ion. What does the term placenta refer to? Name and draw various types ofplacenta ions in the flower as seen in T.S. or V.S.

Answer:

                  Placenta is a flattened, cushion like tissue on which one or more ovules are attached. The various types of placenta ion seen in the flowers are described in the following table

Type of Placentation	Description with example	Diagram
Marginal	There is a single placenta which develop along the junction of two fused margins, e.g., pea.
Axile	Mutlicarpellary, syncarpous gynoecium inward growth of carpel's margin forms a multicarpellary condition that contains an axis in the centre. Placenta arises from central axis bearing ovules. e. g., Solanum, China rose.
Parietal	The number of placenta corresponds to number of fusing carpels. Sometimes the ovules bearing placenta grow inward to form false septa and thus ovary becomes bilocular(e.g., mustard) and trilocular e.g., Cucurbit
Free central	The ovary is unilocular and ovules are borne on the central-axis and not connected to the ovary wall by septum, e.g., Dianthus, Silensa.
Basal	The ovary is unilocular and the single ovule is borne  at the base of the ovary attached by a single placenta, e.g., sunflower, wheat.