Botany lecture notes

Receptacular vs Appendicular Theory of Inferior Ovary Development in Flowers

Origin and Evolution of Inferior ovary

Receptacular vs Appendicular Theory
(A Comparative Approach)

Based on the position of ovary there are three types of flowers- (1) Hypogynous, (2) Perigynous, and (3) Epigynous.

(1). Hypogynous Flower: The most primitive type with convex shaped Thalamus (torus). The ovary is superior and all other floral parts (calyx, corolla and androecium) arise from the base of the ovary.

(2). Perigynous Flower: An intermediate or transient type between Hypogynous and Epigynous flowers. The thalamus is more or less cup shaped and the ovary is half inferior, located at the centre of the thalamus cup. All other floral parts arise from the rim of the thalamus cup. Sometimes the thalamus cup forms a long tube like structure called hypanthium.

(3). Epigynous Flower: The most advanced type of flower. The ovary is inferior and all other floral parts arise from the above portion of the ovary.

Ovary Position Classification

(image source: cc wikipedia)

Ø  The origin and evolution of inferior ovary is a well debated question in the phylogenetics of Angiosperms.

Ø  Comparative morphological, anatomical and paleo-botanical studies suggest that the inferior ovary has evolved many times among different groups of Angiosperms in different ways and in different times in the remote past.

Ø  In order to explain the formation of inferior ovary, two theories have developed by the evolutionary biologists.

Ø  The two theories are:

(1). Appendicular Theory

(2). Receptacular (axial) Theory

Ø  Both these theories are proposed on close attention to the organization of the course of vascular bundles supply to the ovules in the flower.

Ø  The two theories also considered that the hypogynous flower is the most primitive one. Moreover, the epigynous condition evolved from a hypogynous condition through the transient perigynous state.

(1). Appendicular Theory

Ø  Proposed by Eames in 1961.

Ø  According to this theory, extensive fusion (both connation and adnation) of the outer lower portion floral whorls to one another and to the ovary wall has occurred. This result in the formation of an inferior ovary (epigynous condition).

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