What is the importance of apomixis and polyembryony? At least 4-5 points.....
Apomixis is a type of asexual reproduction which does not involve fertilization. It does not lead to seed formation.
Importance - 1.Hybrid varieties of seeds can be produced which provide higher and better yield.
2.) Produce better clones and cuttings .
3.) Embryos so formed are generally free from infections .
4) Apomixis prevents the loss of specific characters in the hybrid. Also, it is a cost-effective method for producing seeds.
5) Apomixis is important for crop yield multifold.
Suppose that the crop's yield is 10 tones per hectare. So here, a two-fold increase would mean that the yield is doubled, a three fold increase will mean that yield is increased by three times. Similarly, a multifold increase will mean that the crops yield in increased many a times.
Polyembryony is the process in which the fertilization of single egg leads to the formation of two or more embryos.
Importance: It is important in the formation of identical twins. Formation of embryos by cells of the embryo sac other than the egg. Embryos develop from additional embryo sacs in an ovule.
Although seeds, in general are the products of fertilisation, a few flowering plants such as some species of Asteraceae and grasses, have evolved a special mechanism, to produce seeds without fertilisation, called apomixis. What is fruit production without fertilisation called? Thus, apomixis is a form of asexual reproduction that mimics sexual reproduction. There are several ways of development of apomictic seeds. In some species, the diploid egg cell is formed without reduction division and develops into the embryo without fertilisation. More often, as in many Citrus and Mangovarieties some of the nucellar cells surrounding the embryo sac start dividing, protrude into the embryo sac and develop into the embryos. In such species each ovule contains many embryos. Occurrence of more than one embryo in a seed is referred as polyembryony. Take out some seeds of orange and squeeze them. Observe the many embryos of different sizes and shapes from each seed. Count the number of embryos in each seed. What would be the genetic nature of apomictic embryos? Can they be called clones?
Hybrid varieties of several of our food and vegetable crops are being extensively cultivated. Cultivation of hybrids has tremendously increased productivity. One of the problems of hybrids is that hybrid seeds have to be produced every year. If the seeds collected from hybrids are sown, the plants in the progeny will segregate and do not maintain hybrid characters. Production of hybrid seeds is costly and hence the cost of hybrid seeds become too expensive for the farmers. If these hybrids are made into apomicts, there is no segregation of characters in the hybrid progeny. Then the farmers can keep on using the hybrid seeds to raise new crop year after year and he does not have to buy hybrid seeds every year. Because of the importance of apomixis in hybrid seed industry, active research is going on in many laboratories around the world to understand the genetics of apomixis and to transfer apomictic genes into hybrid varieties.