Question

What is the condition of placenta and ovule in the axile placentation?

Answer 1

Ovary bears ovules on a cushion-like structure called placenta. An ovary may have one or more placenta. The arrangement of ovules on placenta within the ovary is known as placentation. There are various types of placentations occurring in a plant viz marginal, axile, parietal, free central and basal.

Complete answer:
Gynoecium is the last whorl of the flower. It is the female reproductive part of the flower which is composed of one or more carpels. Carpels may be free or fused. When the carpels are free then they are said to be apocarpous as in lotus and rose. When the carpels are fused then they are said to be syncarpous as in mustard and tomato.
The arrangement of ovules on placenta within the ovary is known as placentation. Types of placentations are:
(i) Marginal placentation- The placentation in marginal placentation forms a ridge along the ventral suture of the ovary. The ovules are borne in two alternate rows along the ridge. An example of this type of placentation is the pea plant.
(ii) Axile placentation- In axile placentation, the placenta is present in the axial position and the ovules are attached to it in a multilocular ovary. Some examples that have axile placentation are china rose, tomato and lemon.
(iii) Parietal placentation- The ovary is one-chambered that is unilocular but becomes two-chambered due to the formation of the false septum. The ovules develop on the inner wall of the ovary or on the peripheral part. Some examples of this type of placentation are mustard and argemone.
(iv) Free-central placentation- The ovules are borne on the central axis and septa are absent in the ovary. Some examples of this type of placentation include Primrose and dianthus.
(v) Basal placentation- The placenta develops at the base of the ovary. It has a single ovule attached to the placenta. This placentation is the characteristic feature of the Asteraceae family. E.g. sunflower and marigold.

Note:
Members of the Asteraceae or Compositae family have flower heads composed of many small flowers, called ray- florets that are surrounded by bracts. Bell-shaped disk-florets form the center of each head. Some species have flowers with only disks or only ray florets. The sepals have been reduced to a ring of hairs, scales, or bristles that is called the pappus on the mature fruit.