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Reproduction in Flowering Plants

Types of Ovules:

 

 

 

 

On the basis of mutual relationship between funicle, chalaza and micropyle, there are six types of ovules :

 

  • Orthotropous or atropous : Such ovule is erect or straight so that the funicle, chalaza and micropyle lie on one and same vertical line. This is the most primitive type of ovule, e.g., Polygonaceae, Piperaceae, Casuarinaceae, Urticaceae, etc.
  • Anatropous : The body of the ovule is completely inverted so that micropyle and hilum come to lie very close to each other. The micropyle and the chalaza, but not the funicle, lie on the same straight line. It is the most common type of ovule found in angiosperms (82% families).
  • Hemianatropous or hemitropous : It is intermediate between ortho and anatropous types of ovule with the body of ovule lying at right angles to funiculus. Micropyle and chalaza lie on the same straight line, e.g., members of Ranunculaceae, Primulaceae, and some members of Brassicaceae.
  • Campylotropous : The body of ovule is bent in such a way that micropyle gets directed downwards and is not in straight line with chalaza, e.g., Capparidaceae, Chenopodiaceae, Caryophyllaceae, some legumes and some members of Brassicaceae like mustard, Capsella, etc.
  • Amphitropous : The body of ovule is curved in such a way that embryo sac also gets curved and becomes horse-shoe shaped, e.g., Papaveraceae, Alismaceae, Butomaceae, etc.
  • Circinotropous : The ovule is initially orthotropous but becomes anatropous due to unilateral growth of funicle. The growth continues till the ovule once again becomes orthotropous. In this manner, the funicle takes a complete round around the body of ovule, e.g., prickly pear (Opuntia tuna), members of Plumbaginaceae.

 

 

 

Sub Topics of Reproduction in Flowering Plants

 


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