Reproduction in plants is the production of new individuals or offspring in plants which can be achieved by either asexual or sexual reproduction. Asexual reproduction is where the new organisms are formed without the fusion of gametes; these individuals are genetically identical to their parents plants and each other. Sexual reproduction occurs with the fusion of gametes, these organisms are genetically different from the parents.
Vegetative reproduction and sexual reproduction are the two types of reproduction seen in plants.
- Vegetative reproduction is a type of asexual reproduction where a new individual is produced without the production of seed or spores.
- Sexual Reproduction involves the production of male and female gametes. Fusion of these gametes results in the embryo which grows into a new plant.
In case of vegetative reproduction any plant part that is capable of regeneration can reproduce a new individual. All plants cannot reproduce by vegetative methods while all plants cannot reproduce sexually.
Plants show two main types of asexual reproduction in which new plants are genetically identical to the parent. Asexual reproduction plants are by vegetative means and by apomixis. Vegetative reproduction involves regeneration of any plant part while apomixis is a replacement for sexual reproduction and occurs in many plant species.
- Vegetative reproduction is a process which is naturally found in most herbaceous and woody perennial plants. It typically involves the structural modification of the stem or roots and leaves in a few species.
- There is no mingling of cells or nuclei in asexual reproduction; there is development of fragments into new organisms.
- Plant bodies like liverworts and mosses regenerate to form new plants.
- During the course of evolution plants have developed modified cells, or organs which function as organs of asexual reproduction. These structures reproduce new individuals without the union of gametes.
- Spores which are air borne are characteristic feature of most non-flowering plants like mosses, liverworts and ferns. These asexual spores may grow directly into new individuals.
- In plants like mosses, liverworts, ferns, lycopods and seed plants specialized organs like buds or gemmae serve as organs of sexual reproduction.
- Somatic organs like of flowering plants like stolons, tubers, rhizomes, corms, and bulbs, leaves of succulent plants, dormant buds of moss serve as organs of reproduction.
- Stolons or horizontal roots like in strawberry form new plantlets when they make proper contact with moist soil surface.
- Branching of rhizomes results in multiplication of the plant. Tubers if under proper conditions develop into new individuals.
Sexual reproduction in plants depends on a complex series of basic cellular events, which involves chromosomes and genes and takes place in an elaborate sexual apparatus that develops new plants that are different genetically from the two parents.
- Sexual reproduction involves the union of sex cells and their nuclei and the process of meiosis. The union of the sex cells results in the production of zygote.
- The gametes involved are haploid and form a diploid zygote upon fusion. The union of the gametes is known as fertilization.
- Plant may be hermaphrodites in which the gametes are produced by the same organism or they may be unisexual where the plant produces either male or female gamete but not both.
- The diploid zygote developed by the fusion of male and female gametes develops by mitotic cell division into a multicellular sporophyte.
- The mature sporophyte produces spores by meiosis and forms single sets of chromosomes.
- In plants like the mosses and liverworts the gametophytes are relatively large and the sporphyte is smaller and is never separated from the gametophyte.
- In ferns, gymnopserms and angiosperms the gametophytes are smaller and the sporophytes are much larger.
Plant reproductive system refers to any of the system either sexual or asexual by which the plants reproduce. The end result of reproduction is the continuation of species. The reproductive ability is conservative but has changed moderately to adapt during the course of evolution.
- Reproduction in plants is either sexual or asexual.
- Asexual reproduction in plants involves diverse methods to produce new plants which are identical to their parents.
- Sexual reproduction depends on a complex series of basic cellular events which involves chromosomes and genes and it takes place within a sexual apparatus which is evolved for the development of new plants and is different from the two parents involved in their production.
- Asexual reproduction involves the union of cells or nuclei and hence there is no mingling of genetic traits.
- Asexual reproductive system is of two types and the systems where the systems that utilize almost any fragment or any part of plant body and systems depend upon specialized structures that have evolved as reproductive agents.
Flowers are the reproductive organs of plants. The function of a flower is to effect reproduction and it is by the process of fertilization. A typical flower consists of different wholrs which have specific functions as reproductive organs of the plants.
- The outermost whorl of the flower is called the calyx and consists of sepals.
- Sepals form a protective covering around the protecting bud and they are usually green in color.
- The whorl next to the calyx is the corolla; it is made of the petals which help to attract the pollinators.
- The calyx and corolla make up the perianth.
- The next whorl is the androecium which consists of male organs called stamens.
- The innermost layer of the flower is the gynoecium which consists of the female organs called the carpels.
- Some plants change their morphological expression depending upon a number of factors like age, time and also on environmental conditions.
- Sexual morphology on plants varies within the populations of some species.
In the plant life cycle mitosis occurs in spores, produced by meiosis, they germinate into the gametophyte phase. There is alternation of generations in plants where the sporophyte phase is succeeded by the gametophyte phase. In the sporophyte phase, the spores are are produced in the sporangium by meiosis. In the gametophyte phase, gametes are produced within the antheridium or the archegonium by the process of mitosis.
Life Cycle of Gymnosperms
- The gymnosperms have a sporophyte dominant life cycle. The gametophyte stage in short-lived in gymnosperms.
- Gametophytes develop within the spore wall.
- The microgametophytes mature to form microspores and produce sperm cells.
- The Megaspores develop into megagametophytes which are retained in the ovule.
- The pollens are transferred physically by pollinating agents.
- The pollen grain enter the ovule through the micropyle, they mature inside the ovule to produce sperm cells.
- There are two types of fertilization in gymnosperms and there is more than one embryo initiated in each gymnosperm seed.
- The mature seed comprises embryo and the female gametophyte and serves as food supply and the seed coat.
Life Cycle of Flowering Plants
- When the conditions are favorable for a seed to germinate, it breaks open and the embryo starts to grow.
- Root grows down to anchor the plant in the ground. Roots aids in take up of water and nutrients from the soil, they also store food.
- The shoot grows upwards and develops into a stem which carries water and nutrients form the roots to the rest of the plant body.
- The stem also bears leaves so that they can absorb sunlight. The leaves use sunlight to make food by the process of photosynthesis.
- At the maturity the plant produces flowers. The flowers are reproductive organs that are involved in sexual reproduction which includes pollination and fertilization.
- Pollination is the process in which the pollen is carried by pollinating agents from the anther to the stigma. The pollen moves from the stigma to the ovules.
- After the process of fertilization the male gamete in the pollen grain moves to the ovule where they combine with the female gametes. This process is called fertilization.
Asexual Reproduction vs Sexual Reproduction
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Comparison of asexual reproduction and sexual reproduction: