Plant Stem - Definition, Structure and Functions: Types, Parts

What Is Plant Stem?

The plant stem is an essential constituent of the structure of plants and provides support to leaves, flowers, and fruits in a plant. Further, it forms the principal part about which the entire plant structure and functionality can rightly be visualized as undertaking physiological processes. The structure and functions of stems would be beneficial in understanding growth patterns and adaptation of plants.

Structure Of A Stem

It has three primary tissue types, each with various functions. These are the following:

Dermal Tissue

• The protective outer layer of a stem is made of dermal tissue.

• Mainly, it is the epidermal cells that perform several activities.

• They protect against abrasion and pathogens.

• Gases—oxygen and carbon dioxide—are exchanged between plants and the atmosphere through small openings, the stomata.

• Water Regulation: This waxy layer on the surface helps prevent the loss of water.

Ground Tissue

Ground tissue fills the space between dermal and vascular tissues. It consists of various types of cells, which include:

• Parenchyma Cells: They take part in the storage, photosynthesis, and restoration of tissues.

• Collenchyma Cells: They give flexible support to the plants, mostly to young stems.

• Sclerenchyma Cells: They provide rigid support to plants because of the thick nature of their cell wall.

Vascular Tissue

Vascular tissue is responsible for transporting water, nutrients, and food throughout the plant. It consists of:

• Xylem: Transports water and dissolved minerals from the root to the rest of the plant.

• Phloem: This transports the sugars formed as a by-product of photosynthesis from the leaves to other parts of the plant.

Functions Of The Stem

Stems are responsible for doing a lot of important critical functions that help the plant survive and reproduce, hence grow in the process. These include the following:

Support

The normal function of the stem is to provide support to the plant structure and hold leaves, flowers, and fruits in an upward direction to make sure that there is adequate sunlight and air.

Transport

The stem acts as a part of the vascular system of the plant. Stems promote the flow of water, nutrients, and food through the transport system which keeps the metabolic functions of the plant intact.

Storage

Some stems, particularly those of some species, can store nutrients and water for use when necessary.

Growth

The stem contains meristematic tissues; these are areas of actively dividing cells. Using these tissues, a plant can grow in height and form branches of increasing girth.

Protection

Some stems will grow thorns or other protective structures that help to deter herbivores from damaging the plant.

Types Of Stems

Based on features and growth habits, stems may broadly be classified into various types, for example:

Aerial Stems

They are the most frequent kind of stem which rises above the ground. They bear leaves and flowers and are sometimes distinguished by:

• Herbaceous Stems: Green and soft; it is usually found in annual plants.

• Woody Stems: Hard and rigid; common in trees and shrubs.

Underground Stems

These are stems that are found below the soil surface. They are involved in food storage and vegetative reproduction. Examples include:

• Rhizomes: Horizontally underground stems which form new shoots and roots.

• Tubers: Swollen stems found underground that act as storage organs for nutrients. An example is potatoes.

• Corms: Short and swollen stems that act as storage organs.

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