Types of Placentation
In Angiosperms, ovules are present inside the ovary. Placenta is a special type of tissue, which connects the ovules to the ovary. The mode of distribution of placenta inside the ovary is known as placentation. Some important types of placentation are as follows:
This type of placentation is seen in bi- or multi carpellary, syncarpous ovary. The carpel walls meet in the centre of the ovary, where the lacenta are formed like central column. The ovules are borne at or near the centre on the placenta in each locule. eg.Hibiscus.
It occurs in a monocarpellary, unilocular ovary. The ovules are borne along the junction of the two margins of the carpel. eg.Fabaceae
This type of placentation is found in multi carpellary, syncarpous, unilocular ovary. The carpels are fused only by their margins. The placenta bearing ovules develop at the places, where the two carpels are fused. eg. Cucumber
It is seen in bicarpellary syncarpous, and unilocular ovary. The placenta develop directly on the receptacle, which bears a single ovule at the base of the ovary. eg. Asteraceae.
This type of placentation occurs in a multicarpellary, multiocular ovary. The ovules are borne on placentae, which develop all round the inner surface of the partition wall eg. Nymphaeaceae