Introduction
The kingdom Plantae consists of a diverse and varied group of plants that have been discovered and classified to date. It includes trees, shrubs, conifers, and even moss. This group is further subdivided into Angiosperms, gymnosperms, pteridophytes, bryophytes, and algae. This classification has been done based on external and internal features, such as morphology, anatomy, structure, phytochemistry, and so on.
Hence, considering the vast scope of this topic, we will limit our discussion to angiosperms only.
So, what are Angiosperms?
Angiosperms are a type of vascular plant that bears both flowers and fruits. These types of plants also contain ovules enclosed in an ovary. The ovule, once fertilized, develops into seeds, which then mature into fruits.
The flowers in plants of these species help in pollination and protect the ovaries and the embryos, whereas fruits aid in seed dispersal.
If you were to imagine any type of flower, you are almost certainly imagining an angiosperm. Even though gymnosperms biologically also have flowers, the angiosperms have a much broader diversity of more obvious flowering structures. Although angiosperm plants demonstrate an incredible diversity of flowers, the basic structure of a flower remains the same, regardless of species.
Angiosperms have evolved the ability to manipulate other organisms to carry pollen to the right place. These pollinating animals include insects, birds, and bats that carry pollen to the right place by chance. Many flower petals even have stripes that act like a runaway to direct pollinating insects to their centers and some of these runaways are only visible in the UV spectrum, which is visible to most insects.
Gymnosperms have separate male and female cones, whereas angiosperms have both male and female reproductive organs in the same flower structure. The method of double fertilization generates a diploid zygote that will become the new sporophyte. Then, the second sperm cell fuses with two extra cell nuclei that accompany the egg cell. An endosperm is created from this triploid structure, and it is this endosperm that becomes the seed. It provides nutrition for the zygote as it grows into an embryo.
The ovary surrounding the zygote swells to form a protective coating called the pericarp, which we are familiar with as a fruit after double fertilization generates the zygote and endosperm. This is the major difference from the naked seeds of gymnosperms. The fruits of angiosperm come in a huge variety of shapes and sizes. Usually, the shape of the seed is designed to fit the type of seed dispersal the plant relies on. For instance, bright red berries will attract the attention of birds, who will then ingest the berries and carry the seed for miles before depositing them with their fecal material.
Other angiosperm pericarps become tough nuts that squirrels will bury in the ground. Some angiosperm fruits even grow with lots of hooks on the outside. The significant thing these different fruits have in common is that they protect the seeds inside them while helping move the seed to a new location. There are an estimated 250,000 species of flowering plants in the world, of which trees, shrubs, and herbaceous plants are there. Angiosperms are a diverse group of plants with over 250,000 species recorded.
FAQs on Angiosperms
1. What are the Two Major Groups of Angiosperms?
The two major groups of Angiosperms are monocotyledons and dicotyledons.
2. What are Angiosperms?
Angiosperms are flowering plant species that have specially developed reproductive parts to protect their seeds. One of the general characteristics of angiosperms is that plants belonging to this group have specialized vascular tissue to carry out essential functions such as photosynthesis, nutrition.
3. What is a Characteristic Feature of an Angiosperm?
One of the features of angiosperms or flowering plants is that they rely on animals for the pollination process.
4. What is the Definition of Angiosperm?
Angiosperms can be defined as flowering and fruit-bearing plants which have specially evolved reproductive organs.
5. What are the basic features of a flower?
The small green leaf-like structures between the flower and the stem are called sepals. The sepals cover the flower and protect it when it is still a bud before it blooms. After a flower opens, the sepal helps provide the flower with structure and stability.
The petals are usually the most colourful parts of the flower and also the most specialised structures. Petals are often brightly coloured to attract animals that facilitate the process of pollination or the movement of pollen between flowers.
6. What happens when a flower is pollinated?
When the flower is pollinated, the pollen tube grows down through the style. Pollen tube genesis occurs when the sperm cell divides into two. At the bottom of the style is the ovary, these will grow as eggs, in which the female gametophytes develop. In angiosperms, both of these sperm cells play an important role in fertilization. Due to this phenomenon, this process of fertilization in angiosperms is known as double fertilization. This works when one sperm cell fertilizes the egg.
7. What are the male and female reproductive parts of a flower?
The male reproductive parts are called stamens and the female reproductive parts are called pistils. The stamen or male reproductive part in a flower consists of two parts: the anther and the filament.
The filament supports the anther or pollen head. The pollen gets produced and released in the anther. The filament is often long enough and the anther sits above the top of the pistil even though most angiosperms employ mechanisms to favour cross-pollination to enhance genetic variability.
The pistil, which is the female reproductive structure, like a flower, also consists of several parts: the ovary, style, and stigma.
8. What are angiosperms and how are they defined?
Angiosperms are the second kind of seed-bearing plant. They are called spermatophytes and are also known as flowering plants. The flower petals vary in size and colour considerably. Some flower petals are shaped in a different way that attracts or exude certain pollinators, like the tube-shaped trumpet flowers. They can only be pollinated by moths with very long tongues. Sometimes, the sepals and petals are just protective structures surrounding the important reproductive parts of the flower to protect them from natural consequences.
