Morphology of flowering plants

Morphology is the branch of science that deals with the study of structure, features, and form of organisms. The structural diversity of flowering plants (Angiosperms) always fascinates us but even with their structural diversity, they have some common features. These are roots, stems, leaves, flowers, fruits, and seeds. Thus, the morphology of all angiosperms shows the presence of these five common features.

Studying morphology of plants helps us understand the various structures of plants, but if you happen to observe a plant carefully, you will understand that all plants have root and shoot systems and within that, the plant may or may not bear flowers and fruit. Plants that bear flowers are flowering plants or angiosperms. The common characteristic of angiosperms is that their seeds are enclosed by an ovary which is found inside a flower or fruit.

Flowering Plants or Angiosperms

Approximately 80% of the living species of plants are flowering plants or angiosperms. They are the most diverse group with a population of around 300,000 species. Angiosperms are believed to have a gymnosperm ancestry. Through the course of evolution, a few extinct ferns may have developed into a flowering plant through various steps.

Flowers in angiosperms are the part that encases either male or female reproductive organs or both of them. These reproductive organs participate in sexual reproduction and the fertilized egg which further develops into a seed is enclosed in the ovary within the flower. Evolution and development of various features like a flower and a vascular system consisting of specialized cells and tissues have made the Angiosperms adaptive to the various niche of terrestrial habitats.

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With their extensive diaspora, flowering plants form an important part of the ecosystem, like most animals, birds, and humans depend on them. Angiosperms differ from other plants in several ways. The presence of a flower is the first basic differentiation. The flower is the reproductive organ of the flowering plant. Their method of reproduction is called pollination. It is the process in which pollen grains are transferred from anthers to the stigma of the flower where the zygote is formed by fertilization.

Detailed Morphology of Flowering Plants

Plant morphology tells us that every plant has two systems. A root system and a shoot system. The root system dugs deep into the ground and forms a system of its own. The shoot system, on the other hand, is the one which is above ground level and comprises various plant parts. 

Root System

The descending part of the plant, which grows under the soil roots. During germination, the radicle from the seed grows downward and branches out. The branches together with the primary root are called the root system. Roots lack chlorophyll and hence they are not green in color. Roots are positively geotropic and hydrotropic, that is, they grow towards ground and water and negatively phototropic, which is growing away from light.

There are three types of root systems found in plants

1.  Taproot System

Dicots mainly have this type of root system, where the primary root grows from the radicle of the germinating seeds. Other roots sprout laterally from the primary root in this kind of root system. Taproot system provides the plant a very good anchorage and the taproot grows deep into the soil.

Examples- Mango, Mustard, Gram, Etc.

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2.  The Fibrous Root System

The fibrous root system is shown by monocots where the roots develop into a thin and dense network. These types of roots do not penetrate deeper into the soil. They remain close to the surface. Hence, they cannot provide strong anchorage like Taproots. The branching roots may also grow from a primary root in some plants, but the primary root is short-lived. The roots arise from the radicle and plumule of the growing plant with this type of root system. Some plants may also have a combination of taproots and fibrous roots.

Examples- Wheat, Paddy, Onion, Maize, Etc.

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3. The Adventitious Root System

Adventitious roots arise from the plant parts other than the radicle of the plant. Monocots mostly have the adventitious root system. Roots arise from stems, leaves, shoots, or any other plant part in this case. Adventitious roots develop normally or under conditions of stress. They are rather a part developed to sustain extreme conditions. The conditions of stress might be drought, absence of nutrients, or physical wounds. Adventitious roots provide vegetative propagation, support, etc.

Examples- Banyan Tree, Maize, Oak Tree, Black pepper tree, beetle tree, etc.

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Functions of Root

The four major functions of the roots are as follows

 1. Provide anchorage- Roots penetrate inside the ground and hold the plant upright and in one place. Therefore, they provide anchorage to the plants.

2.  Absorptions of essentials- Roots being hydrotropic, spread under the ground in search of water and nutrients. They absorb the essential minerals necessary for plant growth from the ground as well as water.

3.  Storage- Apart from Absorption, roots also store the food and nutrients for the plant.

4.  Translocation of essentials- Roots translocate water and minerals to the stem.

Shoot System

The shoot system is the ascending part of the plant that grows above ground level. It bears various essentials plant organs like the stem, leaves, nodes, internodes, etc. The shoot system develops from the plumule of the germinating seed. Shoot system of the flowering plant is composed of the stem, leaves, flowers, and fruits.

Stems

Stems provide axial stability to plants. They grow above ground and are autotrophic. They grow away from the soil and in the direction of light. The apex of the stem contains a terminal bud. Young stems are green in color. As the plant grows into a tree, the stem develops a protecting covering which is brown in color and tough.

Morphology of stem of angiosperms

Morphology of stems puts light on the two main factors, nodes, and internodes. Nodes are the points where the plant bear leaves and internodes are the areas between the nodes. The arrangement of leaves on the stem comes under the study of phyllotaxis. Thus, according to phyllotaxy, one leaf per node is called a spiral arrangement, one leaf per node with a divergence of 180 degrees is the alternate arrangement. Two leaves per node are called the opposite arrangement, and more than two leaves per node are called a whorled arrangement.

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Modification of Stem

Apart from axial stability, the stems of plants under certain conditions undergo modification. The modified stems provide protection, vegetative propagation, food synthesis, and other such functions to keep the plant healthy and growing despite the changing conditions.

Various modifications of the stem are-

  • Suckers

  • Runners

  • Climbers

  • Tubers

  • Tendrils

  • Thorns

  • Bulbils

  • Cladode

  • Rhizomes

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Leaves

Leaves are the food factory of the plant. They grow in the presence of sunlight and contain the green pigment chlorophyll, essential for food production. Apart from making food, leaves store the food, play an important role in transpiration, and carry out the exchange of gases. Leaves arise from the apical bud and grow on the nodes of the stem. They encase a vascular system consisting of a network of veins that carry nutrients to different plant parts.

Various parts of the leaf are- Leaf base, petiole, and lamina.

Leaf Modifications

A part of the leaf or the whole leaf undergoes modifications under certain conditions to perform specific functions. In some carnivore plants, the leaf traps the prey for the plant. In some, leaves modify into protective buds.

Here are various leaf modifications

  • Tendrils and hooks

  • Spines

  • Insect catching leaves

  • Storage leaves

Flowers

Flowers are the reproductive part of the flowering plants. They are vibrant, colorful and most have a sweet smell. This is to attract insects and birds to them, which in turn act as carriers or vectors for the transport of pollen grains. By the process of pollination (Cross and self-pollination), they reproduce. Flowers or a bunch of flowers are arranged in a definite pattern on the floral axis. This phenomenon is called the inflorescence. The inflorescence is of two types- Racemose and cymose inflorescence.

A flower has four different whorls

  • Calyx- the outer part

  • Corolla- the petals

  • Androecium- consisting of the stamens

  • Gynoecium- consisting of one or more carpels

The ovary of the flower plays a vital role. They develop into fruits that contain seeds.

Fruits

Fruits develop from flowers and on the basis of mode of their development, they are classified as-

  • Simple fruits- It indicates one fruit developed from the ovary of one flower. Example – Plums, peaches, etc.

  • Aggregate fruits- Many ovaries of one flower produce many small fruits, and the cluster of such tiny fruits is called aggregate fruits. Example- Strawberry, Custard Apple, BlackBerries, etc.

  • Multiple fruits- When ovaries of different flowers develop closely together to form a single big fruit, it is called multiple fruits. Example- Pineapple, Figs, Mulberries, etc.

Seeds

The seed is an integral part of the flowering plant. It is found enclosed within the fruit of the plant. The seed has a protective layer outside called the seed coat which covers the embryo. Depending upon the number of cotyledons present inside the seed, they are classified as Monocotyledons and Dicotyledons.

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  • Monocotyledons- The seed which consists of only one embryonic leaf are monocots. Example- Rice, millet, onion, corn, ginger, banana, etc.

  • Dicotyledons- The seed which consists of two embryonic leaves or two cotyledons are dicots. Example- Beans, peanuts, tomatoes, etc.

FAQ (Frequently Asked Questions)

Q1. Name different types of the root system with examples

There are three main types of root systems, namely

  • Taproot system- Example: Mango, mustard, gram, etc.

  • Fibrous root system- Example: Wheat, paddy, maize, etc.

  • Adventitious root system- Example: Banyan tree, black pepper tree, etc.

Q2. What is Phyllotaxis?

Phyllotaxis is the study of the arrangement of leaves on the stem. There are four different types of phyllotaxis. one leaf per node is called a spiral arrangement, one leaf per node with a divergence of 180 degrees is the alternate arrangement. Two leaves per node are called the opposite arrangement, and more than two leaves per node are called a whorled arrangement.

Q3. What is inflorescence?

Flowers are arranged in a definite pattern on the floral axis. This phenomenon is called the inflorescence. The inflorescence is of two types- Racemose and cymose inflorescence.