Angiosperm Life Cycle - Overview, Defination, Stages
The angiosperm life cycle presents a different case of alternation of generations where both the haploid (n) and diploid (2n) phases can be seen. The diploid plant (the sporophyte) in this cycle produces small haploid structures called gametophytes. The male gametophyte is the pollen grain, and the female gametophyte is the embryo sac within the ovule. When the stigma of a flower receives pollen, it grows a pollen tube that transports the male gametes to the ovule, where fertilisation occurs. This results in the development of a zygote (which will become the embryo) and an endosperm (which will feed the developing embryo).
This Story also Contains
- What Are Angiosperms?
- Angiosperm Life Cycle Steps
- Process of Fertilisation in Angiosperms
- Recommended video on "Angiosperms"
.jpg)
It is found that the process of endosperm formation (which is triploid) is exclusive in angiosperms and is one of the main reasons they are so successful. Research also shows that angiosperms developed approximately 140 million years ago, and the double fertilisation of their seeds helps in offering additional nutrition to the seed, thus increasing its chances of survival. Compared to this, gymnosperms, such as pine, do not similarly develop an endosperm, and their seeds mature more slowly. This life cycle difference between angiosperms and gymnosperms is an important aspect of plant evolution that scientists are researching today.
What Are Angiosperms?
Angiosperms, or flowering plants, are the most abundant plants on the planet. They bear flowers and seeds covered in a fruit. Angiosperms occur nearly everywhere forests to deserts, and contribute to the ecosystem by offering food, oxygen, and shelter. Their specialised reproductive system helps in quicker seed development and survival in various conditions.
- Angiosperms have well-developed leaves, stems, and roots.
- Their seeds form in an ovary, which is the fruit.
- They have a wide range of flower sizes, shapes, and colours to attract the pollinators.
- Angiosperms may be climbers, shrubs, trees, or herbs.
- They contain significant crops such as rice, wheat, maize, and fruits.
Also Read:
Angiosperm Life Cycle Steps
The stages of the angiosperm life cycle begin with the formation of male and female gametophytes, where microspores develop into pollen grains and megaspores form the embryo sac. There are several steps that take place during this entire process. Each step is discussed in detail in the table given below:
Stage/Process | Expalanation |
|---|---|
Seed Stage | The seed consists of an embryo, a seed coat, and stored food. Monocots have one cotyledon while dicots have two. |
Seed Germination Process | Germination occurs through imbibition, enzyme activity, and sprouting of the radicle and plumule. |
Seedling Stage | The root system develops for anchorage and nutrient absorption, while the shoot system grows upward. |
Vegetative Growth Stage | Leaves develop to increase surface area for photosynthesis, essential for plant growth. |
Photosynthesis and Plant Growth | Light energy is converted to chemical energy, providing the necessary resources for growth and development. |
Reproductive Stage | Flowers develop as the plant transitions to reproduction, containing structures for gamete generation. |
Pollination | Self-pollination occurs within the same flower or plant, while cross-pollination happens between different plants. |
Fertilization | The process of combining male and female gametes to form a zygote. |
Double Fertilization Process | One sperm fertilises an egg another sperm fuses with two polar nuclei to form endosperm. |
Fruit and Seed Development | The ovary develops into a fruit, which protects seeds and helps in their dispersal. |
Seed Dispersal Mechanisms | Seeds are dispersed by wind, water, animals, or mechanical ejection. |
Process of Fertilisation in Angiosperms
Angiosperm fertilisation is the union of a male gamete (sperm cell) from pollen with the female gamete (egg cell) in the ovule. This occurs within the ovary of the flower following pollination. Angiosperms have a different characteristic of double fertilisation, where one sperm unites with the egg to give rise to a zygote, and the second sperm unites with two polar nuclei to give rise to the endosperm that feeds the embryo.
The fertilisation process is described below in the table:
| Process | Explanation |
|---|---|
| Pollen Tube Formation |
|
| Fusion of Gametes |
|
| Formation of Zygote and Endosperm |
|
Recommended video on "Angiosperms"
Other Useful Resources:
Frequently Asked Questions (FAQs)
The life cycle of an angiosperm involves alternation of generations, including a dominant diploid sporophyte stage and a haploid gametophyte stage. Key processes include spore formation, gametophyte development, fertilization, seed development, and germination.
The five stages of growth in angiosperms are:
- Seed Stage - Formation of seeds containing an embryo and stored food.
- Seed Germination - The process where seeds absorb water and begin to sprout.
- Seedling Stage - Development of roots and shoots for anchorage and nutrient absorption.
- Vegetative Growth Stage - Leaf development to increase photosynthesis surface area.
- Reproductive Stage - Flower development leading to pollination and fertilization.
Angiosperms reproduce through the following steps:
- Pollination - Transfer of pollen from the anther to the stigma of a flower.
- Fertilization - Fusion of male and female gametes to form a zygote.
- Double Fertilization - One sperm fertilizes the egg, while another sperm fuses with two polar nuclei to form endosperm.
- Seed Development - The zygote develops into an embryo within the seed, while the ovary matures into fruit.
- Seed Dispersal - Seeds are dispersed by various mechanisms such as wind, water, or animals to grow into new plants.
Angiosperms are the only plant group significantly used in agriculture. Thus, the fertilization procedure always has a significant economic impact. They assist in transforming the zygote's genetic identity. Ovules become seeds after fertilization, and ovary tissue develops into the fruit. In addition, angiosperms are the only organisms with double fertilization. Endosperm tissue is produced, serving as a food reserve and supplying the growing embryo with nutrition. The viability of the seed is thus increased even further.
A diploid zygote develops inside an ovarian ovule if pollination and fertilization take place. The zygote transforms into an embryo inside a seed, which arises from the ovule and also contains food to feed the embryo. The ovary that contains the seed may grow into a fruit. Fruits draw animals that could spread the seeds they contain. If a seed germinates, it might develop into an adult sporophyte plant and continue the cycle.
Angiosperms are a group of flowering plants that produce seeds enclosed within a carpel, which is a specialized female reproductive organ. They represent the largest and most diverse group of plants, comprising about 300,000 species and accounting for approximately 80% of all known green plants.
Male gametophytes are cleaved by meiosis to produce haploid microspores inside the microsporangia of the anthers. Pollen grains are created as a result of this proceeding via mitosis.
Fruit trees, such as those that produce the mango, apple, banana, peach, cherry, orange, and pears, frequently display flowers before they bear fruit. Bees are typically responsible for pollinating these trees.
Additionally, angiosperm includes grains including wheat, corn, and rice. These plants use the wind to carry out the pollination process. In addition, there are sugarcanes, roses, lilies, broccoli, kale, petunias, eggplant, tomatoes, and peppers that are angiosperms.
Some species are monoecious (stamens and pistils are present on separate blooms, but the same plant), some are dioecious (stamens and pistils are present on separate flowers), and some (staminate and pistillate flowers occur on separate plants). Anatomical and environmental obstacles both encourage cross-pollination that is mediated by a physical agent (wind or water) or an animal, such as a bug or bird. Cross-pollination broadens a species' genetic diversity.