Both Gametophyte and Sporophyte are the two Generations of a plant.
Gametophyte: Gameto means gametes and phyte means plants. The generation of plants that forms gametes is called gametophyte. Plants produce gametes with the help of their sex organs. Every plant such as bryophyte, angiosperms, gymnosperms, algae, etc. go through this. For example, algae produce simple and non-motile gametes inside its body. Spirogyra produce gametes inside their bodies and transfer gammetes to another spirogyra through conjugation. Bryophyta has antheridia and archegonia which are sex organs to make gametes. Similarly, pteridophytes and gymnosperms also consist of archegonia which are developed in different manners. Angiosperms makes gametes when pollen grain development takes place. Thus, gametophyte generation is experienced by most of these plants.
Sporophyte: Sporo means spores and phyte means plants. The generation of plants that produce spores is called sporophyte. Algae, bryophytes, angiosperms and gymnosperms all of these make spores. A spore is a tiny structure that leads to a new plant after its germination. Spores can be of two types, namely mitotic spore and meiotic spore. Mitosis and meiosis are types of cell divisions which lead to the formation of these spores. Mitotic spores are asexual spores and meisotic spores are called sexual spores. Sporophyte can make both kinds of spores; algae is a simplified organism and forms mitotic or asexual spores, similarly chlamydomonas also form asexual spores. Bryophytes form meiotic or sexual spores, homosporous pteridophytes form same size of spores from spore mother cell and heterosporous pteridophytes form two different kinds of spores, namely microspore from microspore mother cell and megaspore from megaspore mother cell. Similarly, heterosporous gymnosperms and angiosperms form their spores.
Alternation of generations is a life cycle that includes both haploid and diploid multicellular stages. It is divided into two parts N haploid and 2n diploid. It was discovered by Strasburger. It is the conversion of gametophyte generation into sporophyte generation and vice versa.
Diploid means two sets of chromosomes (2n), one set of chromosomes from male parents and another set of chromosomes from female parents. On the other hand, haploid means one set of chromosomes (n) (that carry genetic information). Multicellular contains more than one cell and unicellular is containing only one cell. In plants, lifecycle is completed by multicellular haploid cells whereas in humans, it is undergone through unicellular haploid cells.
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Below is a Tabular representation highlighting some of the differences between Sporophyte and Gametophyte stages of the Plant Life Cycle.
Sporophyte generation produces spores.
Gametophyte generation results in the formation of gametes.
It uses the meiosis process.
It uses the mitosis process.
These consist of diploid plants.
These consist of haploid plants.
Sporophytes have two sets of chromosomes.
These have a single set of chromosomes.
These reproduce asexually.
These reproduce sexually.
During meiosis, diploid spore mother cell results in the formation of haploid meiospores.
Gametes take part in fertilization or fuse together to give rise to diploid (2n) zygote.
1. What does it mean that Gametophytes are Dominant?
Ans. It means that the gametophytes phase of the plant can prepare its own food and doesn’t depend upon sporophytes for any nutrient. On the other hand, sporophytes depend upon gametophyte for food and are weaker than the gametophytic phase.
2. Explain the event in the Life Cycle of a Flowering Plant.
Ans. Following events take place during the life cycle of a flowering plant.
Germination: It is the stage when a plant begins to grow or germinate from a seed where roots are formed below the soil and the leves, stem and roots appear above the soil.
Pollination: It is the process where the pollen grains carried by wind or insects travel to another flower.
Fertilization: When the pollen reaches the ovary of another flower, the fusion of male gametes and female gametes takes place and the process is called fertilisation.
Dispersal: It is the scattering of seeds by wind or animals and where some of these seeds may emerge into a new plant.
All of these stages in the lifecycle of a flowering plant leads to the beginning of a new plant through a seed. Here, the seed sprouts forming a seedling which in turn is converted into a new plant. It forms new seeds and this way the cycle continues.
3. What are the different stages in the alternation of Generations?
Ans. Alternation of generations between sporophyte and gametophyte takes in the following stages:
Sporangium present in diploid sporophytes undergo meiosis to form haploid spores.
The spore develops into a gametophyte which is haploid in nature.
The gametophyte consisting of reproductive organs undergo mitosis to form haploid gametes.
These gametes fertilize to produce a haploid zygote which matures into a mature sporophyte.
Thus, the cycle keeps repeating and one generation after the other keeps coming, this is called alternation of generations.
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