What are the different types of Ovules ?
Hello Student,
Ovules can be classified as follows :
1. Based on relative position of micropyle
Orthotropous : Themicropyle, chalaza and funicle lie in straight line .This is the most primitive type of ovule. Eg - Polygonum , Cycas
Anatropous : The ovule turns at 180° angle.It is inverted ovule. Micropyle lies close to hilum or at side of hilum.Eg - It is most common form and found in 82% angiosperm families.
Hemianatropous : Ovule turns at 90° angle upon funicle or body of ovule is at right angles to the funicle. Eg - Ranunculus
Campylotropous : Ovule is curved more or less at right angle to funicle. Micropyar end is bend down slightly. Eg Members of Leguminosae , Cruciferae
Amphitropous : Ovule as well as embryo sac is curved like a horshoe shaped magnet. Eg - Lemna, Poppy, Alisama
Circinotropous : The ovule turns at more than 360° angle and thus funicle becomes coiled around the ovule . Eg- Opuntia
2. Based on Number of integuments
Unitegmic: Single integument, Seen in gymnosperms , members of gamopetalae.
Bitegmic : Two integuments , Seen in members of polypetalae, monocots.
Ategmic : No Integument, Seen in Santalum, Loranthus.
