Angiosperms, classification up to class, characteristic features and examples
Angiosperms are vascular plants with stems, roots, and leaves. The seeds of the angiosperm are found in a flower. These make up the majority of all plants on earth. The seeds develop inside the plant organs and form fruit. Hence, they are also known as flowering plants.
Angiosperms are the most advanced and beneficial group of plants. They can grow in various habitats as trees, herbs, shrubs, and bushes.
Characteristics of Angiosperms
Angiosperms have diverse characteristics. The important characteristics of angiosperms are mentioned below:
- All plants have flowers at some stage in their life. The flowers are the reproductive organs for the plant, providing them with a means of exchanging genetic information.
- The sporophyte is differentiated into stems, roots, and leaves.
- The vascular system has true vessels in the xylem and companion cells in the phloem.
- The stamens (microsporophyll) and the carpels (megasporophyll) are organized into a structure called the flower.
- Each microsporophyll has four microsporangia.
- The ovules are enclosed in the ovary at the base of the megasporophyll.
- Angiosperms are heterosporous, i.e., produce two kinds of spores, microspore (pollen grains) and megaspores.
- A single functional megaspore is permanently retained within the nucellus.
- The pollen grains transfer from the anther to stigma and reproduction takes place by pollination. They are responsible for the transfer of genetic information from one flower to the other. The pollen grains are much smaller than the gametophytes or reproductive cells present in the non-flowering plants.
- The sporophytes are diploid.
- The root system is very complex and consists of cortex, xylem, phloem, and epidermis.
- The flowers undergo double and triple fusion which leads to the formation of a diploid zygote and triploid endosperm.
- Angiosperms can survive in a variety of habitats, including marine habitats.
- The process of fertilization is quicker in angiosperms. The seeds are also produced quickly due to the smaller female reproductive parts.
- All angiosperms are comprised of stamens which are the reproductive structures of the flowers. They produce the pollen grains that carry the hereditary information.
- The carpels enclose developing seeds that may turn into a fruit.
- The production of the endosperm is one of the greatest advantages of angiosperms. The endosperm is formed after fertilization and is a source of food for the developing seed and seedling.
Classification of Angiosperms
The classification of angiosperms is explained below:
- The seeds have a single cotyledon.
- The leaves are simples and the veins are parallel.
- This group contains adventitious roots.
- Each floral whorl has three members.
- It has closed vascular bundles and large in number.
- For eg., banana, sugarcane, lilies, etc.
- The seeds of these plants have two cotyledons.
- They contain tap roots, instead of adventitious roots.
- The leaves depict a reticulate venation.
- The flowers are tetramerous or pentamerous and the vascular bundles are organized in rings.
- For eg., grapes, sunflower, tomatoes, etc.
The angiosperms originated about 250 million years ago and comprise 80% of the earth. They are a major source of food for humans and animals.