ARTIFICIAL HYBRIDIZATION

Artificial hybridization:

·         One of the major approaches of crop improvement programme.

·         Only desired pollen grain used for pollination.

·         Stigma is protected from contamination (from unwanted pollen grain).

·         Removal of anthers from the flower bud before the anther dehisces is called emasculation.

·         Emasculated flowers covered by bag generally made up of butter paper, to prevent contamination of its stigma with unwanted pollen. This step is called bagging.

·         If the female flower is unisexual there is no need of emasculation.

Double fertilization:

Double fertilization is a complex fertilization method where out of two sperm cells, one fuse with the egg cell and a third fuses with two polar nuclei which results in diploid (2n) zygote and triploid (3n) primary endosperm nucleus·(PEN) respectively. Since endosperm  is a product of fusion of three haploid nuclei. it is called as triple fusion.         

After entering one of the synergids, the pollen tube releases two male gametes into the cytoplasm of the synergids.

·         Syngamy: one of the male gamete fused with egg cell, to form a diploid zygote.

·         Two polar nuclei of central cell fused to form a diploid secondary nucleus.

·         Triple fusion: The second male gamete fused with the secondary nucleus to form a triploid primary endosperm nucleus.

·         Since two type of fusion, syngamy and triple fusion take place in the embryo sac the phenomenon is termed as double fertilization.

·         The central cell after triple fusion becomes primary endosperm cell and developed into the endosperm.

·         The zygote developed into an embryo.

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DEVELOPMENT OF MALE AND FEMALE GAMETOPHYTE

Microsporogenesis is the process of formation of microspores from pollen mother cell. Megasporogenesis is the formation of megaspores from megaspore mother cell. Functional megaspore develops into female gametophyte.

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POST FERTILIZATION EVENTS

Post fertilization is a series of events that take place after fertilization to develop a seed from an ovule and a fruit from an ovary.

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