What is Gametophyte?
The gameto means gametes and phytate means plants. The generation of planets that form gametes is called gametophytes. Plants produce gametes with the help of their sex organs. Every plant such as bryophyte, angiosperms, gymnosperms, algae, etc. goes through this. For example, algae produce simple and non-motile gametes inside its body. Spirogyra produces gametes inside their bodies and transfers gametes 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 make gametes when pollen grain development takes place. Thus, the gametophyte generation is experienced by most of these plants.
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What is Sporophyte?
Sporo means spores and phytate means plants. The generation of plants that produce spores is called sporophytes. Algae, bryophytes, angiosperms, and gymnosperms 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 that lead to the formation of these spores. Mitotic spores are asexual spores and meiotic 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 from meiotic or sexual spores, homosporous pteridophytes form the 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 the megaspore mother cell. Similarly, heterosporous gymnosperms and angiosperms from their spores.
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Alternation of Generation
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, a 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, the lifecycle is completed by multicellular haploid cells whereas, in humans, it is undergone through unicellular haploid cells.
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Difference between Sporophyte and Gametophyte
Below is a tabular representation highlighting some of the differences between the sporophyte and gametophyte stages of the plant life cycle.
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Summary
In the life cycle of plants, generation change is a common occurrence. As a result, the life cycle is divided into two different phases: asexual and sexual. The sporophyte generation is represented by the asexual phase, while the gametophyte generation is represented by the sexual phase. Furthermore, sporophytes are diploid, meaning they have two sets of chromosomes. Gametophytes, on the other hand, are haploid and have only one set of chromosomes. This is the most important distinction between sporophyte and gametophyte. Additionally, although the sporophyte generates haploid spores, the gametophyte produces male and female gametes. Gametophyte generation is dominant in bryophytes and algae, whereas gametophyte generation is dominating in pteridophytes, gymnosperms, and angiosperms. The distinction between sporophyte and gametophyte is thus summarised.
FAQs on Difference Between Sporophyte and Gametophyte
1. What are the primary differences between a sporophyte and a gametophyte?
The main differences between a sporophyte and a gametophyte lie in their ploidy, reproductive method, and role in the plant life cycle. Here are the key distinctions:
- Ploidy: The sporophyte is a diploid (2n) generation, meaning it has two sets of chromosomes. In contrast, the gametophyte is a haploid (n) generation, with only one set of chromosomes.
- Reproduction: The sporophyte reproduces asexually by producing haploid spores through meiosis. The gametophyte reproduces sexually by producing haploid gametes (sperm and egg) through mitosis.
- Main Function: The sporophyte's function is spore dispersal, while the gametophyte's function is to produce gametes for fertilization.
- Dominance: In lower plants like mosses, the gametophyte is the dominant, photosynthetic stage. In higher plants like ferns and all seed plants, the sporophyte is the dominant, larger, and more complex stage.
2. What is meant by the alternation of generations in plants?
Alternation of generations describes the life cycle of a plant that alternates between two distinct, multicellular forms: a diploid (2n) sporophyte and a haploid (n) gametophyte. The diploid sporophyte produces haploid spores via meiosis. These spores germinate and grow into a haploid gametophyte. The gametophyte then produces gametes (egg and sperm) by mitosis. The fusion of these gametes during fertilization creates a diploid zygote, which develops into a new sporophyte, thus completing the cycle.
3. In which plant group is the gametophyte the dominant stage, and what does this mean?
The gametophyte generation is dominant in Bryophytes, which include mosses, liverworts, and hornworts. Dominance in this context means that the gametophyte is the most visible, long-lived, and nutritionally independent phase of the life cycle. The green, leafy structure we commonly identify as a moss is the gametophyte. The sporophyte, in contrast, is typically smaller, short-lived, and remains attached to and dependent on the gametophyte for nutrition.
4. How do the sporophyte and gametophyte stages differ in ferns?
In ferns, the sporophyte is the dominant generation. It is the large, complex plant with well-differentiated roots, stems, and leaves (fronds) that we typically recognise as a fern. It produces spores in structures called sori. The gametophyte, known as a prothallus, is a small, heart-shaped, free-living organism that is photosynthetic but significantly smaller and simpler than the sporophyte. Although independent, the gametophyte is short-lived, and the new sporophyte grows out from it after fertilization.
5. Why is the evolutionary shift from a dominant gametophyte to a dominant sporophyte significant?
This shift is a major evolutionary advancement for plant life on land. A dominant diploid (2n) sporophyte offers several advantages. Having two sets of chromosomes masks the effects of harmful recessive mutations, providing greater genetic stability. Furthermore, the evolution of a larger sporophyte with specialized tissues like vascular systems (xylem and phloem) allowed plants to grow taller, compete more effectively for sunlight, and efficiently transport water and nutrients, enabling them to conquer diverse terrestrial habitats far from water sources.
6. What are the main functions of the sporophyte and gametophyte generations?
Each generation has a distinct primary function essential for completing the plant's life cycle. The main function of the sporophyte (diploid phase) is to produce and disperse haploid spores over a wide area, facilitating colonization. The main function of the gametophyte (haploid phase) is to produce male and female gametes and facilitate their fusion (fertilization) to create a new diploid zygote, which then develops into the sporophyte.
7. Are there any similarities between a sporophyte and a gametophyte?
Yes, despite their many differences, the sporophyte and gametophyte share some fundamental similarities. Both are multicellular stages in the plant life cycle, a key feature of alternation of generations. Both are essential for the completion of the life cycle; one cannot exist without the other producing it. In many plant groups, both stages are also capable of photosynthesis, at least for a portion of their existence (e.g., the independent gametophyte and sporophyte in ferns).
