Angiosperms - Defination & Characteristics

Introduction To Angiosperms

A most diverse group of plants on the Earth is the group of angiosperms, which definitely can be distinguished for their ability to produce flowers and encased seeds within fruits. These species are critical in supporting most biomes on the land by offering animals and plants with food, shelter, and homes.

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This Story also Contains

1. Introduction To Angiosperms
2. Characteristics Of Angiosperms
3. Classification And Diversity
4. Morphological Features
5. Reproductive Biology
6. Physiological Processes
7. Recommended Video On 'Angiosperm'

Angiosperms are believed to have had their beginnings during the Cretaceous period approximately ninety to one hundred and thirty million years ago; They have since diversified to the extent of occupying most of the plant niches on earth because of the adaptive advantages offered by the improvements in this kind of plant. These plants are essential in practices such as agriculture, horticulture, medicine, and in maintaining ecological systems so, angiosperms are crucial in the current biological sciences.

Characteristics Of Angiosperms

The predominant features of angiosperms that make them distinctive are as below:

• Flowering organs - these are the reproductive parts of the plant. The flowers help the plant to reproduce without many crossings with related species. It creates several varieties, leading to the vast diversity of species dominating the land.

• Endosperm - the nutritive tissue formed just after fertilisation and zygote formation. It provides necessary food for the growing embryo and the cotyledons till they disintegrate.

• Reduced male gametophyte - the pollens are smaller than those in gymnosperms, making fertilisation faster. It gives angiosperms an advantage in evolution.

• Stamen - they are lighter and more adapted to cross-pollination. It helps in reducing the possibilities of self-pollination, thereby increasing species diversity.

• Carpels enclosing ovules - this helps to prevent self-pollination and fertilisation. The enclosing carpels later turn into fruit, attracting pollinating agents, thereby helping in the dispersion of seeds.

Classification And Diversity

The classification is described below-

Taxonomic Classification

• Kingdom: Plantae

• Division: Angiospermae

• Class: Monocots and Dicots

Major Families And Examples

Angiosperms, or flowering plants, encompass numerous families with diverse characteristics and adaptations:

Fabaceae (Leguminosae)

Fabaceae is one of the biggest Legume plant families some of the plants belonging to this family are beans, Phaseolus, peas, Pisum, and soybean, Glycine Max. Well-known for the property of fixing nitrogen and being economically valuable in farming.

Asteraceae (Compositae)

Some of the plants belonging to Asteraceae are sunflower which is scientifically known as Helianthus, daisy known scientifically as Bellis, and aster known scientifically as Aster. In this, the plant has compound inflorescence that has a large number of small flowers closely grouped.

Orchidaceae

Orchids are very diverse and found almost all over the world; they are some 25,000 in number. Characterized by their delicate and frequently ostentatious flowers that are evolved for specific pollination techniques.

Rosaceae

Some of the plants that fall under Rosaceae are roses, commonly known as Rosa, apples which scientifically are classified under Malus, strawberries which scientifically are classified under Fragaria and Cherries classified under Prunus. Famous for their pulse and the flowers that are eaten raw or cooked.

Lamiaceae (Labiateae)

Mint plants can also be sorted based on the botanical family which includes; mint (Mentha), basil (Ocimum), and sage (Salvia). These are the plants with sweet-smelling leaves and medical uses.

Poaceae (Gramineae)

A large number of important cereal crops are plants of this family such as wheat Triticum, rice Oryza, and maize Zea. Essential in the human diet and for the production of crops.

Morphological Features

Angiosperms, or flowering plants, encompass numerous families with diverse characteristics and adaptations:

Structure Of Flowering Plants

The structure of flowering plants includes:

Roots

Flowering plants have different kinds of root systems such as tap root system and bristle root system. They hold the plant in the ground, take water and nutrients from the soil and contain some supply in them.

Stems

Petioles in flowering plants provide Mechanical support to the plant organs like flowers and fruits, help in the conduction of water and nutrients from roots to the aerial parts and food substances from the leaves to other parts of the flowering plant and sometimes have food storage. It has nodes which are areas of connection of leaves and buds and internodes which are a space between nodes.

Leaves

There are various forms and structures of leaves, such as the type, e.g., simple and compound, and the shape of a leaf, for instance, needle-shaped or broad-shaped. They execute photosynthesis, convert light energy to sugars, and release gases into the surroundings.

Flowers

Flowers are the specialized structures for reproduction in plants belonging to the category of angiosperms. Depending on the species, it may have different levels of complexity and may be branched or unbranched with such structures as sepals, petals, stamen (the male organ of reproduction), and pities (the female organ of reproduction). They ensure pollination to enhance the reproduction process, especially through the development of seeds.

Diagram: Parts Of An Angiosperm (Labelled)

Reproductive Biology

Flowering plants exhibit complex reproductive strategies centred around their flower structures:

Flower Structure And Pollination Mechanisms

The mechanism of pollination is described below:

Pollination

Pollination is the process through which pollen grains with male gametophytes are placed on the stigma part of the female reproductive organ, the style while the anther is the male reproductive organ. It can occur through various mechanisms:

• Types of Pollination: There are two types of pollination- self-pollination, which is pollination by pollen from the same flower or another from the same plant and cross-pollination which is the transfer of pollen from the flower of one plant to another.

• Agents of Pollination: The pollination techniques include anemophily or wind pollination, entomophily or insect pollination, ornithophily or bird pollination, mammalophily or mammal pollination, and hydrophily or water pollination. The colour, fragrance and nectar presentation of flowers also vary to correspond with the following pollinators.

Fertilisation Process

Once pollen comes in contact with a compatible stigma, the pollen tube germinates and grows down the style or the stalk of the pistil and reaches the ovule, the structure within the ovary contains the female gametes. The male gametes reach the female gametes by pollen tube to impregnate the ovule part which is enveloped. This process of fertilization causes the development of a zygote into an embryo within the seed coat.

Diagram: Flower Structure and Reproductive Process

Physiological Processes

The physiological process of angiosperms is described-

Photosynthesis

The angiosperms directly capture light in chlorophyll found in chloroplasts to synthesize glucose and oxygen from carbon dioxide and water. Besides, this process facilitates the growth and development of plants and also plays an important role in oxygen generation and the earth’s carbon cycle.

Respiration

The flowering plants use glucose derived from photosynthesis for the production of ATP through aerobic respiration. This process takes place in mitochondria and is pertinent to the overall cellular process of nutrition, growth and division.

Transpiration

Transpiration is the process of loss of water vapour from tissues of plants particularly stomata in the leaves. This process has the effect of developing a pressure deficit at the upper end which drives the upward movement of water and dissolved nutrients from the roots to the shoots. Transpiration is responsible for cooling the plant's level, preserving the internal pressure of plant cells, and transporting minerals to different parts of the plant.

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