Home > Plants > Life Cycle of Plants

Life Cycle of Plants

life-cycle-of-a-plantA lifecycle describes how a living thing starts its life, grows to maturity, reproduces, and restarts the cycle. All living things including plants follow a specific lifecycle which keeps their species alive.

What is the Plant Life Cycle?

Plants are living things, they grow and reproduce like any other living thing. They also follow a cyclic process in various stages like starting a new life, growing, and then coming back to the starting stage (reproducing). Plants start their life from seed and grow up to become mature plants.

Stages of Plant’s Life Cycle

Most of the plants start their life as seeds. These seeds are buried in the ground by various methods, where they germinate. After germination, the first leaves of plants, known as seedlings, emerge. After that, further growth of the plants begins until they reach maturity. At this stage, plants pollinate and produce seeds so that their species continue to survive by restarting the life cycle.

The life cycle of plants can be broken down into 3, 4, and 5 stages. But the most widely accepted model has 5 stages.

  • Seed
  • Germination and Seedling
  • Growing to Maturity
  • Reproductive Stage
  • Seed Dispersion

Seed – 1st Stage

sunflower-seed
sunflower-seed

Seeds are the embryos of plants that contain the necessary food for early development. They are housed in a tough outer coating for protection until conditions are just right for germination.

These seeds are dispersed across the land in many ways, such as moving water, wind, animals, and human activity. When seeds reach a suitable environment with adequate moisture levels and the right temperature, they germinate and start their lifecycle.

Germination and Seedling – 2nd Stage

sunflower-seedling
Sunflower seedling

After the germination, a seed breaks its outer coating and grows the first Roots and leaves, known as cotyledons. Once initial structures from the seed come out of the soil, it is called a seedling.

At this stage, the roots begin to absorb water from the Soil, while the leaves start photosynthesis for food production. The seedling continues further development and forms plumules. These plumules are early stems from which new leaves develop.

Growing to Maturity – 3rd Stage

mature-sunflower-plants
Mature sunflower plants

The seedling growth continues until the plant reaches full maturity. The plant needs many necessary things for healthy growth such as water, nutrient-rich soil, air, sunlight, the right temperature, and adequate spacing from other plants. (For details check How Plants Grow?).

When plants mature, they develop stronger roots and a large number of branches and leaves. At this stage, they are ready to enter the reproductive stage to make flowers and new seeds.

Reproductive Stage – 4th Stage

parts-of-flowerWhen plants mature, they produce flowers from modified shoots known as determinate Apical Meristem. A typical flower is composed of the following reproductive parts:

  • Stamen (Male Parts): Produces the pollen (a powdery substance) required for the fertilization of the pistil.
  • Pistil (Female Parts): Produces seeds after fertilization

When the pollen from the stamen reaches the pistil, fertilization happens and seeds are produced in the process.

Seed Dispersion – 5th Stage

seed-dispersion

After seeds are produced, the plants must disperse their seeds to favorable places where they can germinate and begin a new life cycle. There are several methods for seed dispersion:

  • Wind: Strong blows of wind pick the seeds from the plants and carry them away. Moreover, light seeds with fibers glide in the air and reach distant places.
  • Water: When seeds of plants fall into the river, they are carried away to distant places.
  • Animals: Fruits of plants are eaten by animals that contain seeds. Later on, animals excrete the seeds at different locations.

Pollination Methods

cross-pollination
cross-pollination

The process of pollination in which pollen reaches the pistil from the stamen happens through several methods:

  • Insect Pollination: insects visit the flowers to drink sweet nectar. They move from flower to flower and unknowingly transfer pollen from the stamens to the pistils.
  • Wind Pollination: Many plants have male and female parts separated by a large distance. The wind plays a crucial role in carrying pollen from the stamen to the pistil during strong blows.
  • Animal Pollination: Animals, including birds and land animals, play a role similar to insects. They also visit the plants for food and carry the pollen that sticks to their bodies. They transfer pollen from the stamens to the pistils while moving between plants and their flower.

What about Seedless Plants?

spores-of-fern
Spores of fern on its leaves

Many plants don’t produce flowers or seeds for reproduction. Instead, they grow from the spores of their parent plants. Spores can be parts of a plant or the remains of a dead plant. New plants are produced from the spores and continue to grow.

See Non-Flowering plants for further information.

FAQs

What is Self-Pollination and Cross-Pollination?

In self-pollination, the pollen from the anther reaches the stigma in the same flower, or a different flower in the same plant. However, cross-pollination is a bit different. It happens when the pollen from the anther of one plant reaches the stigma of another plant’s flower having the same species. Both of these processes can happen naturally as well as artificially.

What is the Asexual Reproduction of Plants?

The plants which grow without fertilization are called asexually reproduced plants. Asexual reproduction can occur from fragmentation, spores, budding, and vegetative propagation. Potatoes are a famous example of the asexual reproduction of plants.

What is the Alternation of Generations?

The life cycle of plants is divided into two main phases; the haploid and the diploid. These two phases of the plant lifecycle can also alternate and this process is called the alternation of generations.

The alternation of generations is the primary type of lifecycle in plants. In this lifecycle, the haploid sexual phase (gametophytes) which consists of only a single set of chromosomes turns into a diploid asexual phase (sporophytes) which contains two sets of chromosomes. Both haploid and diploid are multicellular and their cells split by meiosis and mitosis process of cell division respectively. This alternation of generation is not only common in plants but also found in algae and Fungi.

Interesting Facts

  • Great Basin bristlecone pine is the longest-living plant found in the world. Its age is measured to be around 5,056 years.
  • Coco de Mer is the seed of a palm tree, it can weigh about 18 Kg (40 pounds) and reach a height of 12 feet.
  • Rose, Jasmine, and Lily are the strongest-smelling flowers.
  • When a seed is not germinating, it is in a dormant state. In this stage, it is no more than dead stuff.

You Will Also Like

flowering-plant
Flowering Plants
plant-structures
Plant Structure
Plants are the living things that grow from tiny seeds or spores to mighty trees. They start their life as a weak creature that thrives on ground and water to grow. The starting point of their life is due to a process called germination. Germination allows the seeds – and also spores – to sprout and become a seedling (very young plant). Parts of a Seed Before discussing the process of germination, it is important to know about the parts of seeds. There are 3 main parts of the seed, which are: 1. Seed Coat – The first things you can see on a seed is its coat – also called seed coat. It is usually a hard outer layer that protects the seed from damage. Also, many kinds of seeds have a soft seed coat that can easily be damaged by pressing them with hands. 2. Embryo – The embryo is the actual part of a seed that grows from the cells that it contains to become a plant. It has 4 main parts, which are epicotyl, hypocotyl, radicle, and cotyledons. 3. Endosperm – The endosperm is like a food storage for the seed. It usually surrounds the embryo of the seed, and it provides all the necessary food (starch and protein) until the seed germinates to a seedling. Conditions for Germination Seeds depend on the environmental conditions for germination. Some seeds successfully germinate, while others don’t. Germination needs a right condition to sprout the seeds. The most important environmental conditions that need to be at the right level are water, temperature, oxygen, and light or darkness. Let’s discuss each of these environmental conditions. • Water – The germination process highly depends on the amount of water present in the soil. Because seed coat is usually dry, it needs to be moistened by water to break its coating. Furthermore, when the water is absorbed in the seed, it activates the certain enzymes. These enzymes break down the stored food and convert it into useful chemicals that supply energy to the embryo. • Temperature – Each kind of seed needs a different range of temperatures to germinate. Some seeds germinate in cold temperatures, while others require hot temperatures for germination. The seeds usually don’t germinate if the temperature is not favorable. • Oxygen – seeds use oxygen during metabolism when germinating. Majority of the seeds are buried in the soil. Seed usually take oxygen from the spaces in the soil until they grow their leaves for photosynthesis. If a seed is buried at a great depth, then it is difficult for the seed to get oxygen. • Light or darkness – It is not an important factor to consider. Because the majority of the seeds have no any effect of light or darkness. But, some seeds have the impact of light. The light or darkness usually trigger the germination process for these seeds. Process of Germination Germination of seed follows four main changes that are occurred in steps. These steps are imbibition, respiration, Mobilization of food reserves, and development of the embryo into a seedling. Let’s discuss each of these steps in detail. 1. Imbibition – This is the first step that starts with the absorption of water – also called imbibition. As the seed absorbs the water through small pores in its seed coat, it rehydrates and swells. The swelling of the seeds forces the seed coat to break, which allows the radicle (first root) to come out and absorb nutrients from the soil. 2. Respiration – When water enters into seed, it starts the metabolic activities in the embryo. The oxygen is absorbed by the seed from the soil for generating energy. Oxygen provides the necessary energy to the seed until it grows leaves and starts photosynthesis. 3. Mobilization of Food Reserves – During germination, metabolism takes place. The seed needs food for digestion. The food of the seed is usually stored in the endosperm. The food is mobilized from the endosperm to the embryo. The outer layer of the endosperm secretes the special enzymes that are used for digestion. 4. Development of Embryo into Seedling – The transportation and digestion of food cause the cells of the embryo to develop and divide. The embryo grows until it forms into a seedling. The seedling has every necessary part to start photosynthesis and further grow into the mature plant. Rate of Germination When the seeds are planted in an agricultural area or garden – not every seed in germinated. To measure how many seeds have been germinated from total seeds, it is called germination rate. Germination rate is usually in percentage, which describes how many seeds have been germinated in a given amount of time. For example, 100 seeds are planted in a garden and 65 seeds have been able to germinate. Then, the rate of germination will be 65%. Facts • The seeds of proteas have the unusual ability. They start to germinate after they are exposed to smoke. This ability is definitely evolved in them for surviving in fire-catching forests. • Coco-de-Mer is a seed that has a weight of around 30 kg. It is considered as largest seed on the earth. • Not every plant grows from the seeds. Many plants grow from the spores of their parent plant. Spores are the remaining of a plant after it dies, or they may be the parts of a plant.
Seed Germination
growing-plant
How Plants Grow
flower
Flower
Non-Flowering Plants
Non-Flowering Plants