«Биология негіздері» «Основы биологии»
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- Fertilization Process
| Fertilization Definition
Fertilization is the process of fusion of the male and female gametes to develop a new individual. In plants, fertilization is after pollination of the carpel, there is germination of the pollen grain and a pollen tube grows and travels to the ovary. The pollen grain adheres to the stigma, a pollen tube grows and penetrates the ovule and the pollen tube burst into the embryo sac . Fertilization Process The pollen grain germinates after the carpel is pollinated. From the germinated pollen grain, a pollen tube emerges and grows. It travels and grows and moves towards the ovary by creating a path through the female tissue. Two types of nucleus, the vegetative tube and generative nuclei of the pollen grain pass into the pollen tube. Stigma secretes a sugary substance that stimulates the growth of the pollen tube. The pollen contains the vegetative and the generative nucleus and the cell ruptures the stigma and passes through the style. The pollen grains attaches itself to the stigma of the female reproductive structure, the pollen tube grows and enters the ovule making a tiny pore called a micropyle. The pollen tube does not reach the ovary in a straight line. The pollen tube grows near the style and curls to the bottom of the ovary and then near the receptacle. The pollen tube then breaks into the ovule through the micropyle and then the micropyle bursts into the embryo sac. In the embryo sac, on the male nucleus fuses with the nucleus of the egg and forms a diploid zygote. This process is known as true fertilization or syngamy. The other male gamete or nucleus enters further into the embryo sac and it fuses with secondary nucleus. This gives rise to a triploid nucleus called the primary endosperm nucleus. This process of nuclear fission, where there is formation of primary endosperm nucleus is called triple fission. After the process of fertilization the ovary swells up and develops into a fruit. In case of fruits with multiple seeds, multiple pollen grains are necessary to fertilize with each ovule. The pollen tube growth is controlled vegetative cytoplasm. To digest the female tissue, the pollen tube produces hydrolytic enzymes as the tube moves down towards the stigma and style. The tissue digestive by the hydrolytic enzymes acts as a nutrient source for the pollen tube. жүктеу/скачать 408,88 Kb. Достарыңызбен бөлісу:
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