Megasporangium

Megasporangium /intro/ types / integument

1. Megasporangium :- Types Of Ovules And Integuments Presented by: - Vaghela Bhavubha A. M.Sc sem-2 (Botany) Paper :- CBO-404 Dept . Of life Sciences H.N.G.U., Patan

2. CONTENTS Introduction of megasporangium Types of Ovules
Integuments Reference

3. Introduction of Megasporangium The megasporangium or the Ovules located within the ovary , arise from the placentae , consists of nucellus and integument. It is attached to the placentae on the inner wall of the ovary by means of stalk called funicles. A mature Ovule shows an opening called micropyle and the basal region of the Ovule where the funicles is attached is called hilum. Within the nucellus a female gametophyte or the embryo sac is present.

4. Fig. Ovule Showing different parts

5. Types Of Ovules Mature Ovules are classified in to six types based on the position of micropyle with respect to funicle and chalaza , which are as follow :- . (1) Orthotropous Or Straight (2) Anatropous Or Inverted (3) Hemitropous Or Hemianatropous (4) Campylotropos Or Curved (5) Amphitropous Or transverse (6) Circinotropos

6. (1) Orthotropous Or Straight In this type the Ovule is erect or straight so that the funicle, chalaza, micropyle lie one and the same vertical line, as in members of polygonaceae and piperaceae.

7. (2) Anatropous Or Inverted In this type the Ovule bends along the funicle so that the micropyle lies close to the hilum. The chalaza lies at the other end. This is the commonest type of Ovule found both in monocots and dicots.

8. (3) Hemitropous Or Hemianatropous In this type the body of the Ovule is straight but twisted in such a way that it is placed transversely at right angle and so the chalazal , micropyle line is at right angle to the funiculus. It is found in Ranunculus.

9. (4) Campylotropous Or Curved In this type the transverse Ovule is bent round like a horse-shoe so that the micropyle and the chalaza do not lie in the same line, as in cappsris, Cruciferae , Mirabilis jalapa etc.

10. (5) Amphitropous Or Transverse In this type the Ovule is placed transversely at a right angle to its stalk or funicle, as found in Alismeceae , Butomaceae.

11. (6) Circinotropous Type Initially the Ovule is Orthotropous type but with continuous unilateral growth the Ovule becomes Anatropous and subsequently the micropyle again points upward in fully mature Ovule as in opuntia and plumbago.

12. Integuments Usually the Ovule possesses either one (unitegmic) or two (bitegmic) integuments. The number is constant in most families, and rarely unitegmic and bitegmic Ovules occur in same family. In the Archychlamydeae and monocotyledons most genera possess two integuments (I.e., bitegmic) but a few possess only one .

13. The unitegmic Ovule is characteristic of sympetalae , where it is generally massive in structure. In some plants a third integuments or aril is also present. In many plants the outer integuments becomes fleshy or juicy and is known as sarcotesta.

14. Reference A Textbook of Botany- Embryology of Angiosperm - By B.P. Pandey www.megasporangiumimages.com