Gametophyte and Sporophyte

The life cycle of a plant involves the alternation of two generations: gametophyte and sporophyte generations. However, what is the difference between gametophyte and sporophyte phases? How are they different from one another and what are their distinguishing factors?
When you're studying the life cycle of plants, fungi and protists, you will come across the term alternation of generations. This alternation of generation refers to the alternation of two phases: a multicellular diploid phase alternating with a multicellular haploid phase. These generations are phases in the reproduction cycle of the plant. One is sexual while the other is asexual. There are several difference between gametophyte and sporophyte stages. Let us have an individual look at them to understand them better.

Sporophyte (2n)

This phase in the life cycle of a plant is the asexual, spore bearing generation of the plant, featuring diploid cells. This means the cells of the plant in this generation or phase have two sets of chromosomes in their cells. The zygote or fertilized cell is what conduces to form the sporophyte.

By the process of meiosis (reduction division), this sporophyte produces haploid spores. Since spores are formed in this generation, the name given to this phase is sporophyte. The haploid spores produced will then form the next gametophyte generation by growing into multicellular, haploid individuals called gametophyte.

As we learned above that the zygote or fertilized cell is diploid, however, the spores formed by them are haploid. This takes place because of reduction division or meiosis that take place. Meiosis is a process in which the number of chromosomes in each cell is cut down to half and the following cells formed will have half the number of chromosomes of their parent cells.

Gametophyte (n)

The other alternating phase in the life cycle of the plant is the gametophyte generation, in which gametes are formed. This is that phase of the plant in which the gametes, that is the egg and sperm formed are haploid (n), having only one set of chromosomes in them. Thus, gametophyte phase is the sexual, gamete producing stage in the life cycle of the plant.

Spores are actually the first cells of the gametophyte generation. These spores undergo the process of mitosis, by which identical cells with same number of chromosomes are formed. Male and female gametes with equal 'n' number of chromosomes are formed. When these gametes meet, they fuse together, get fertilized and form the zygote, which is diploid (2n). Note that the chromosome number here doubles from 'n' to '2n'.

This diploid zygote then forms the basis of the next alternating sporophyte generation. It forms the first cell of the diploid sporophyte generation. This zygote then grows into the sporophyte, which then later forms the haploid spores in the sporophyte generation and the cycle continues in the plant's life cycle.

Gametophyte vs Sporophyte

While considering gametophyte versus sporophyte generations, there are some stark points, such as sporophyte is a diploid phase, whereas gametophyte is a haploid generation. Sporophyte stage is asexual, while gametophyte stage is sexual. The first cell in a sporophyte generation is the diploid zygote, while the first cell in the gametophyte stage is the haploid spore. Then, in the sporophyte phase, haploid spores are formed and in the gametophyte phase, diploid male and female gametes are formed.

As far as dominance is concerned, in liverworts and mosses, the gametophyte stage is the larger and familiar form of the plant, whereas, the sporophyte stage is smaller and is found growing on the gametophyte stage. However, in angiosperms, it's the other way round. The sporophyte phase is the larger and independent phase, while the gametophyte phase is small and reduced to pollen grain and an eight-celled female gametophyte situated inside the ovule.

This alternation of generation is highly significant in plants, as it increases the chances of the plant's survival in the long run. The next generation becomes even more adapted to the environment. The formation of spores from parent cells, cause shuffling of genes, conducing to new, different and stronger genetic make ups. Then in the gametophyte stage, when gametes are formed with no reduction division, the zygote formed is better adapted to the environment. Thus, the gametophyte and sporophyte generations are truly significant phases in the life cycle of a plant.
Published: May 24, 2010
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I want to know about the life cycle of marchantia...but it's not available on this website...can you help me to know about it? - Sudin Joshi [December 22, 2013]
Thanks to the author of this article, I'd be able to pass my biology exam! Thank you so much! :) - Komal [June 1, 2013]
Thanks for your excellent explanation. - Kingsley c [August 25, 2012]
Bryophyte gametophyte produces eggs in female reproductive organ called archegonuim.what produces the sperm? - Kingsley c [August 25, 2012]
thanks for telling the basic difference - neha [March 30, 2012]
Really great ! thank you for the information helps me alot ...more pictures will be more benefit in our studies... - aliti bulai [July 24, 2011]
great - sumit jat kota [May 3, 2011]
Would a picture help solve the question? I tried to send pictures of the main plant, and the smaller plants to my Mac via bluetooth. It failed, but I have done this in the past, so I'll keep trying. Do you have a place to submit pictures with questions? - James Burke [April 8, 2011]
Hello, I have had a plant growing in a pot, for over 30 years. At first I thought it was a palm, because of it's large ark green leaves, and trunk. It suddenly began to root out of the soil to the side, seeking something to grow into. It also began to burn in sunlight. Isn't that what ferns do? I am so confused. Also recently, what appears to be another plant is growing in the soil near it. It is a lighter color, and heart shaped. It doesn't appear to be a weed, and I live in a city apartment, so the chances of something else growing seems odd. If it is a fern, could these be sporophytes? If they are sporophytes how long will they take to mature into gamophytes. They've been in the pot, for about a month now, and are not changing. Only continuing to grow. Now there is 6 offshoots. Do you think that these are Sporophytes or weeds. If they are weeds, how do I kill them, before they take over my plant. This plant used to be my moms, and so it is important to me, that it continues to thrive. Thank you. - James Burke [April 8, 2011]
This really helped, I am learning about this right now and my textbook did not explain it very well. - Catherine [March 14, 2011]
hmmmm,,thank you,,this informations,,are big help to me specially to my studies..^_^ - Catrina Yu [December 8, 2010]