Life Cycles in Plants: Meaning, Types, Diagrams

Every living organism has a life cycle. All living organisms take birth, grow, and reproduce, and this cycle of life continues. Have you ever thought about how this life cycle forms in plants? Like other living things, plants also grow and reproduce and go through a cyclic process of life. The life cycle in plants begins with the germination of a seed. 

The seed grows into a seedling, then a mature plant and the plant produce seeds through reproduction, and again a new life cycle restart. The life cycle of plants can also be referred to as alternation of generation. In this article, we will discuss about life cycles in plants. Scroll down to learn more!

Define Life Cycles in Plants

The life cycle in plants is a series of stages, from the germination of the seed to the completion of reproduction of that plant. It begins with seed germination, seedling, growth of the plant, and production of new seeds. The life cycle pattern in plants is known as alternation of generation.

What are Life Cycles in Plants?

The plant shows two stages in its life cycle; one is the haploid phase, also known as the gametophyte phase, and the second is the diploid phase, also known as the sporophyte phase. These two phases alternate with each other, and this pattern is called the alternation of generations. Alternation of generation is found in plants, algae, fungi, bryophytes, and pteridophytes. Both haploid and diploid cells are divided by mitosis and meiosis in the plant life cycle that forms haploid and diploid plant bodies.

The sequential events that take place in the life cycle of plants:
1. The gametophyte is the haploid plant body that produces gametes by mitosis cell division.
2. After fertilization, the zygote is formed, and divided by mitosis to produce a diploid sporophytic plant body.
3. The haploid spores are produced by the sporophytic plant body with the help of meiosis.
4. The haploid plant body is formed by haploid spores with the help of mitosis.
5. The alternation of generation occurs between the haploid gametophyte and the diploid sporophyte, and this cycle repeats.

Life Cycles in Plants Diagram

Below we have provided the diagrammatic representation of life cycles in plants:

Life Cycles in Plant: Types

Alternation of generation is common in the plant kingdom. There are three basic life cycle patterns:

Haplontic 

1. Predominant phase is gametophytic or haploid \(\left( {\rm{n}} \right).\)
2. Meiosis takes place in the diploid zygote (terminal meiosis).
3. This pattern of the life cycle is present in Volvox, Spirogyra, Chlamydomonas and many other algae.

Fig: Haplontic Life Cycle

Haplo-diplontic (or Diplo-haplontic)

1. Predominant phase is the haploid (gametophyte) with the prominent diploid phase (sporophyte), as in Mosses and Liverworts. This is called the haplo-diplontic life cycle.
2. Predominant phase is the diploid (sporophyte) with the prominent haploid phase (gametophyte), as in Pteridophyta. This is called the diplo-haplontic life cycle.
3. Meiosis takes place during spore formation (intermediate meiosis).
4. This pattern of the life cycle is present in all Pteridophytes and in some algae like Ectocarpus, Polysiphonia, Kelps.

Fig: Haplodiplontic Life Cycle

Diplontic

1. Predominant phase is diploid \(\left( {{\rm{2n}}} \right)\) and sporophytic.
2. Gametophyte is not independent and reduced.
3. Meiosis takes place during gamete formation (initial meiosis).
4. This pattern of the life cycle is present in all seed-bearing plants (Gymnosperms and Angiosperms) and in Fucus (an alga).

Fig: Diplontic Life Cycle

Life Cycle Stages in Flowering Plant

Flowering plants are flower-bearing plants. The flowering plants go across their life cycle in multiple stages: Germination, Pollination, Fertilization, and Dispersal.

1. Germination

This is the first stage where the plants begin to grow from the seed. In this, the root from the seed grows under the soil and upper body stem and leaves above the soil.

2. Pollination

This happens when the pollen of one flower is carried by wind or butterfly or an insect to another flower of the same species.

3. Fertilisation

When the pollens meet the stigma of other flowers and travel to the ovary where it forms male and female gametes, fertilisation occurs.

4. Dispersal

In this stage, the seeds are dispersed or scattered by wind, animals, and water. These seeds again form a new plant.

Fig. Life Cycle of a Flowering Plant

Interesting Facts

Some of the interesting facts about life cycles in plants are as follows:

1. Plants that live and keep on making new seeds every spring and summer are called Perennials.
2. Plants that get mature and die every season are called Annuals.
3. Why are some flowers colorful and have fragrance?  This is to attract butterflies and insects towards them, which helps in pollination.

Summary

Plants are also considered living things, and for survival, they reproduce and grow. They perform a cycle of life that begins with the germination of a seed to the reproduction of a new seed. This entire process goes through multiple stages. In this article, you will come to know how a plant performs its life cycle from seed formation, growing to seedling, growth of plant and reproduction process. This life cycle in the plant continues.

FAQs on Life Cycles in Plants

Q.1. What are the 3 life cycles of a plant?
Ans: The 3 life cycles of a plant are: \(1\). Haplontic, \(2\). Haplo-diplontic (or Diplo-haplontic) and \(3\). Diplontic.

Q.2. What are the 6 stages of a plant life cycle?
Ans: The life cycle in plants shows 6 stages. These are seed, germination, growth, reproduction, pollination, and seed spreading stages.

Q.3. What do you understand by the alternation of generations?
Ans: Plant shows two stages in their life cycle. One is the haploid phase, also known as the gametophyte phase, and the second is the diploid phase, also known as the sporophyte phase. These two phases alternate with each other, and this pattern is called the alternation of generations.

Q.4. Name the haploid phase in the life cycle of plants.
Ans: The gametophytic phase is the haploid phase in the life cycle of plants.

Q.5. Explain Diplontic Life Cycle.
Ans: Diplontic Life Cycle:
a. Predominant phase is diploid and sporophytic.
b. Gametophyte is not independent and reduced.
c. Meiosis takes place during gamete formation (initial meiosis).
d. This pattern of the life cycle is present in all seed-bearing plants (Gymnosperms and Angiosperms) and in Fucus (an alga).

Q.6. What do you mean by sporophyte generation?
Ans: Sporophyte generation is the phase in the life cycle of certain plants and algae that starts with the union of gametes up to the time that spores are produced.

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