Plant Life Cycles and Alternation of Generations

The Plant life Cycle consists of two generations that alternate with each other and thus this process is known as the alternation of generations. The two types of generation which take place are known as sporophyte generation and gametophyte generation. Sporophyte generation is a stage that generates haploid spores by the process of mitosis whereas in gametophyte generation the gametes are produced in the plants.

What is Alternation of Generation?

The alternation of generation is also known as heterogenesis or metagenesis. The type of life cycle in which the subsequent generation alternates between the two different life stages or generations is known as the alternation of generation. Therefore they alternate between the haploid and diploid organisms. These two stages of alternation of generation are known as Gametophyte generation and Sporophyte generation. This type of life cycle can be seen in algae, plants, and fungi.

Plant Life Cycle and Alternation of Generation

In plants, alternation of generation means the life cycle of plants in which the number of generations of plants can be distinguished between haploid and diploid organisms. The life cycle in living organisms has been categorized into three different types which are mentioned below:

• Haplontic: Haploid cells are the independent stages that give rise to new individuals. The life cycle of organisms that are dominated by the haplontic stage is known as the Haplontic life cycle. For example: In algae, haplontic type of life cycle is shown.
• Diplontic: In the diplontic life cycle the diploid zygotes which are formed through the fertilization of gametes are independent and when they are divided mitotically they give rise to new plants. Example- Gymnosperms and angiosperms.
• Haplo-diplontic: This is a type of life cycle where sporophyte and gametophyte both are multicellular. For example – Bryophytes are gametophytes whereas Pteridophytes are sporophytes.

Alternation of Generation- Life Cycle

These are some of the stages that occur during the alternation of generation are mentioned below:

• Diploid sporophyte consists of a structure known as sporangium.
• Meiosis takes place in the sporangium which results in a formation of haploid spores.
• The spores evolve into gametophytes which are haploid in their nature.
• A gametophyte consists of reproductive organs which undergo mitosis to give rise to haploid gametes.
• The gamete fertilizes, then it forms a haploid zygote.

Types of Stages in Alternation of Generation

There are two types of stages in alternation of generation which are mentioned below:

Sporophyte Generation

A diploid zygote is formed when two haploid gametes fuse together which results in the formation of a sporophyte. In sporophyte generation multiple rounds of mitosis are needed to produce an organism which will be multicellular. After reaching maturity phase the reproductive organisms are formed which are said to be sporangia. Further these sporangia are used in the creation of haploid spores. At last these spores are dispersed and carried away by water and air to form a gametophyte.

Gametophyte Generation

After the sporophyte this is the next generation in alternation of generation. In this, the spore is newly formed which consists of only half of DNA of the parent organism which undergoes mitosis numerous times to form a gametophyte. These types of gametes are formed by gametangia. Whenever these gametes come in contact with the opposite sex they together produce a zygote which forms into a sporophyte. They are generally found in ferns.

Flowering Plants Life Cycle Events

A flowering plants undergoes different types of life cycle events which are been discussed below:

• Germination: It is the first process in the plant’s life cycle. The plant begins to grow from a seed where the roots began to grow under the soil from that seedling after sometimes the stem and leaves formed above the soil.
• Pollination: It is a process in which pollen is carried away from one flower to another flower by the insects or wind.
• Fertilization: Fertilization is a process in which the pollen goes to the ovary of the flower where the fusion of male and female gametes took place.
• Dispersal: Seeds are dispersed by animals and wind. New plants are formed from some of these seeds.

FAQs on Plant Life Cycle and Alternation of Generation

1. What do you mean by Alternation of Generation?

Alternation of generation is a type of life cycle where there are different number of plant generation which are differentiated between haploid and diploid organisms.

2. What are the Types of Stages in Alternation of Generation?

There are two types of Stages in Alternation of Generation:

• Sporophyte Generation
• Gametophyte Generation

3. What are Plant Life Cycles?

Plant life cycle describes about the multiple stages of plants life. The stages of plant life cycle are- germination of seed, pollination, fertilization and dispersal of seed.

4. What are the 3 Life Cycles of a Plant?

The three types of life cycle in organisms are:

• Haplontic
• Diplontic
• Haplo-diplontic

5. What do you mean by Sporophyte Generation?

When two haploid gamete fuse together they form a diploid zygote which further results in a formation of sporophyte. Therefore in plants this phase of their life cycle is known as sporophyte generation.