A plant is a nature’s gift as they provide us with the food, oxygen, shelter, clothing, etc. They are also known as the universal or primary producers. Like all other living things, plant do respire, grow, develop, excrete and reproduce. All higher plants reproduce by fertilization. Fertilization in flowering plants was discovered by Ralph B. Strassburger in the year 1884. Let us have a brief discussion on fertilization.
Fertilization is the fusion of the male and the female gamete produced by the pollen grain to develop into a diploid zygote. It is a physicochemical process which occurs after the pollination of the carpel. The complete series of this process takes place in the zygote to develop into a seed. In fertilization process, flowers play a major role as they are the reproductive structures of angiosperms. The process of fertilization in plants occurs when gametes in haploid conditions meet to create a zygote which is diploid. In the course of fertilization male gametes get transferred to female reproductive organs through pollinators (honey bees, birds, bats, butterflies, flower beetles) and the final product will be the formation of the embryo in a seed.
In flowers, the pollen grain germinates after the pollination of the carpel and grows into the style by creating the pathway for the pollen grain to move down to the ovary. The pollen tube breaks into the ovule through the micropyle and bursts into the embryo sac where the male nucleus fuses with the nucleus of the egg inside the ovule forming a diploid zygote, which later swells up and develops into a fruit.
Types of Fertilization
Fertilization process can be differentiated into three types which are mainly based on the entry of the pollen tube into the ovule.
- Porogamy: A most common type of fertilization which is seen in all angiosperm plants. In this type of fertilization, the entry of the pollen tube into the ovule is through the micropyle.
- Chalazogamy: This type of fertilization is seen in all casuarina plants. In this type of fertilization, the entry of the pollen tube into the ovule is through the pollen tube.
- Misogamy: This type of fertilization is seen in all Cucurbit plants- pumpkin, ridge gourds, bitter gourd and other gourd plants. In this type of fertilization, the entry of the pollen tube into the integuments of the ovule.
Double fertilization is a process of fertilization characterized by the fusion of a female gametophyte with two male gametes. In this mechanism, one sperm cell fuses with the egg-producing zygote, and the other fuses with the two polar nuclei to make the endosperm. All angiosperm plants undergo double fertilization process.
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