Question

what are the post fertilization changes take place in plant

Answer 1

Plant Fertilization
Fertilization is the process of fusion of the female gamete, the ovum or egg and the male gamete produced in the pollen tube by the pollen grain. Fertilization in flowering plants was discovered by Strassburger in 1884. 
Flowers are the reproductive structures of angiosperms. They vary greatly physically and are of great diversity in methods of reproduction. The process of fertilization in plants occurs when gametes in haploid conditions meet to create a zygote which is diploid.The male gametes of the flower are transferred on to the female reproductive organs through pollinators. The final product of this process is the formation of embryo in a seed. 
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.

Types of Fertilization

Depending upon the place of entry of the pollen tube into the ovule, three types of fertilization have been recognized. They are Porogamy, Chalazogamy and Mesogamy.
Porogamy - It the most common type of fertilization seen in angiosperm plants. In porogamy, the entry of the pollen tube into the ovule takes place through the micropyle. 

Chalazogamy - In chalazogmay, the pollem tube enters thorugh the chalaza. It can be seen in Casuarina plants. 


Mesogamy - Mesogamy is seen in Cucurbita plants. Here, the pollen tube enters through the integuments of the ovule. 

Double Fertilization

Double fertilization is complex mechanism of fertilization in flowering plants or angiosperms. Double fertilization is joining of a female gametophyte with two male gametes. One sperm nucleus fertilizes the egg cell and the other sperm combines with the two polar nuclei of the megagametophyte. The haploid sperm and haploid egg combine to form a diploid zygote. The other sperm nucleus fuse with the other two haploid polar nuclei of the megagametophyte to form a triploid nucleus, this develops into a endosperm and is called the primary endosperm nucleus. This entire phenomenon of fertilization that involves the fusion of the egg and one male gamete and the fusion of the other male gamete with the secondary or the polar nuclei is called double fertilization. 

Answer 2

post fertilization is actually the fusion of male and female gamete to form diploid zygote...

there are two changes that occur in post fertilization 1. endosperm development 2. embryogeny

endosperm is actually the type of tissue that is present in the seed of flowering plant during the time of fertilization..it provide nourishment to the young embryo and act as a food for embryo

embryogeny is the process of groeth and development of an embryo form a zygote in flowering plants...and embryogeny is same in both monocot as well as dicot plant.