Plants are living organisms just like animals and exhibit all the characteristics of living organisms that include various processes like breathing, digesting, excreting, reproducing, and so on. Reproduction is a characteristic attribute of plants that enables them to produce new offspring and give rise to their future generations. The genetic makeup of the plant is determined by the mode of reproduction through which it reproduces. The mode of reproduction of plants helps in understanding their exhibited traits.
Before getting into the details of the modes of reproduction, let’s first understand different plant structures. So, various plant structures are classified into –
Vegetative parts that include the roots, stems, leaves, etc.
Reproductive parts that include the flowers.
Asexual Mode of Reproduction – Vegetative parts of the plants gives rise to new plants.
Sexual Mode of Reproduction – Reproductive parts of the plants give rise to embryos which grow into new plants.
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In the asexual mode of reproduction, there is no fusion of male or female gametes. The plants give rise to new plant structures without the fusion of the male and female reproductive parts. This mode of reproduction also doesn’t involve the formation of seeds and fruits.
The plant body produces an outgrowth also called buds. These buds give rise to new plants. The buds essentially grow at a particular site where cell division takes place on the plant body. Budding can be naturally occurring or artificially done in plants. In artificial budding, a bud from one plant is grafted on other plants that result in the growth of new plants from these buds.
Vegetative propagation is the process in which the plant gives rise to a new plant structure, either naturally or manually. A fragment of the parent plant or a specialized reproductive structure in the parent body gives rise to offspring in this type of reproduction.
Apomixis is the replacement of sexual reproduction by the asexual mode of reproduction in plants. In this process, seeds are formed and the embryo also develops but without the fusion of male and female gametes with each other. It’s a process of the formation of an embryo without the process of fertilization. One example of apomixis is the production of egg cells by mitosis. This then develops into an embryo without fertilization.
It is the process in which the parent body divides into fragments to give rise to new individuals. The process of fragmentation can partly turn into asexual reproduction if some of the fragments formed further reproduce by sexual reproduction.
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Angiosperms mostly reproduce by the mode of sexual reproduction. A flower is a reproductive organ in angiosperms. A flower may male or female or both the reproductive organs. Flowers carry out the process of sexual reproduction in plants by bringing about the fusion of male and female gametes to produce the seeds which bear the fruit. The seeds germinate and develop into new individual plants.
Thus, in the sexual mode of reproduction, new plants are produced through the fusion of female and male gametes which produces an embryo. This fusion of gametes leads to the production of seed. These seeds would bear the new plant on germination in the future. The flower can either be bisexual- housing both the male and female organs or unisexual, wherein male and female organs are located in different flowers. Pistil id the female reproductive organ and the stamen is the male reproductive organ in the flower.
Pollination is the type of reproduction that takes place by the transfer of pollen grains. Pollen grains are male microgametophytes that produce the male gametes. So, pollen grains need to be transferred to the stigma of the flower through the anthers. The stigma contains the ovule or the female gametophyte which when fuses with the pollen grains or the male gametophyte produces the zygote. Pollination can be either self-pollination which occurs within the same flower or different flowers of the same plant or cross-pollination which takes -place among flowers of different plants of the same species.
After the transfer of pollen grains, male and female gametes fuse to form the zygote at the ovary of the pistil of the flower.
The zygote thus formed by the fusion of gametes develops into an embryo. The carpels of the flower develop into the fruit tissue. The ovary develops into the fruit and the ovules within bear the seeds of the flower.
Sexual reproduction in plants often requires carriers or vectors for the transfer of pollen grains. These could be biotic or abiotic vectors. The biotic vectors of pollination are bees, insects, birds, etc. and the abiotic factors are wind, air, rain, etc.