Sexual Reproduction In Flowering Plants
Types Of Ovule:
On the basis of Integuments Ovule is of following three types:-
1. Unitegmic Ovule - When only one Integument is present is called Unitegmic Ovule.
2. Bitegmic Ovule - When two Integument is present, then this type of Ovule is called Bitegmic Ovule.
3. Ategmic Ovule - When Integument is absent, then this type of Ovule is termed as Ategmic Ovule.
On the Basis of Nucellus Ovule is of mainly two types:-
1. Tenuinucellate Ovule - Nucellus is in the form of single layer present around the embryo sac or it is less developed type, this is called Tenuinucellate Ovule.
2. Crassinucellate Ovule - Nucellus is multi layered or it is massive type, then such type of Ovule is called Crassinucellate Ovule.
On the basis of relationship among Micropyle, Chalaza and Hilum with the body of Ovule and orientation of these on the Funiculus, Ovule is of six types:-
1. Atropous or Orthotropous - This is a straight or upright Ovule, because the Micropyle, Chalaza, and Hilum lie on the same line i.e., in one straight line.
2. Hemitropous or Hemi-anatropous Ovule - This Ovule is a horizontal type of Ovule, In this the body of Ovule makes 90 degree angle with the funicle and is horizontally situated. The micropyle and Chalaza lie on the same line and Micropyle away from the Hilum.
3. Campylotropous Ovule - The body of Ovule is curved and Micropyle and Chalaza is not present in the same line. The nucellus and Embryo sac is also distorted i.e., curved. The micropyle comes little close to the Hilum.
4. Anatropous Ovule - This is an inverted type of Ovule. In this type of Ovule body of Ovule is turned completely 180 degree to the Funiculus. Micropyle and Chalaza lie on the straight line. Micropyle gets more close to the Hilum. This is a typical type of Ovule found in Angiosperms and it is also the most common type of Ovule.
5. Amphitropous Ovule - This Ovule is known as transverse Ovule. In this type of Ovule curvature is very effective in nucellus, due to this effect Embryo sac becomes horse shoe shaped. The Micropyle and Hilum gets very close.
6. Circinotropous Ovule - This type of Ovule is called as a coiled Ovule. In this type of Ovule funicle coils in such a way that the body of Ovule present on the funicle at 360 degree. Micropyle is far away from the Hilum.