Stem Anatomy

Stem Anatomy

A plant’s shoot system includes stems. They can be a few millimeters long or hundreds of meters long. They can also vary in diameter according to the plant. Although some plants, such as potatoes, have underground stems. Herbaceous or woody stems are seen in nature. Stems serve as a support for the plant, holding leaves, flowers and buds; in rare circumstances.Plant’s stems also function as food storage. A stem can be unbranched or heavily branched. The plant’s stem connects the roots to the leaves, transporting absorbed water and minerals to different plant sections. The stem also aids in the movement of photosynthetic products from the leaves to the remainder of the plant. 

The most commonly found cells in stem and other plant organs are:

• Parenchyma
• Collenchyma
• Sclerenchyma

Parenchyma cells

The most frequent plant cells are parenchyma cells found in the stem, root,  fruit’s pulp and inside the leaf. Photosynthesis is carried out by parenchyma cells, which are responsible for metabolic processes. They also aid in the repair and healing of wounds. In addition, starch is stored in specific parenchyma cells.

Elongated cells

Elongated cells that have unevenly thickened walls make up collenchyma cells. They primarily support the stem and leaves structurally. These cells are still living at maturity and  located beneath the epidermis generally. For example, Collenchyma cells can be seen in the “strings” of a celery stem.

Sclerenchyma cells

Sclerenchyma cells support the plant . Cells of sclerenchyma  die as the plant matures. Fibers and sclereids are two forms of sclerenchyma cells. Secondary cell walls in both types are thickened with lignin deposits, an organic substance that is a significant wood component. Sclereids are smaller than fibers, which are long and slender cells. Sclereids are responsible for the rough texture of pears. Sclerenchyma fibers are used to manufacture linen and rope by humans.

Tissue System

Dermal, vascular and ground tissue are the three tissue systems that make up the stem. Each is defined by distinct cell types that conduct specialized functions essential to the plant’s growth and survival.

Dermal Tissue

The stem’s dermal tissue epidermis is a single layer of cells that protects and covers the underlying tissue. For example, the bark of woody plants is a thick, impenetrable coating of cork cells that shields the plant from harm. Epidermal cells are present in large numbers and least differentiated cells in the epidermis. Gases are exchanged through stomata  in the epidermis of a leaf. Each leaf stoma is surrounded by two cells known as guard cells, which regulate the absorption of carbon dioxide and the escape of oxygen and water vapor by controlling the opening and closing of the stoma. On the epidermis, trichomes are hair-like structures in the stem.

Vascular Tissue

Xylem and phloem make up the stem’s vascular tissue, organized into separate strands called vascular bundles that run up and down the stem’s length. Because they are made up of numerous simple cell types that work together, both are regarded as complex plant tissue. Dicot stems form a ring when we observe the vascular bundles in cross-sections. In plants with stems that live for more than a year, bundles grow individually and produce distinctive growth rings. Monocot stems have vascular bundles that are scattered throughout the ground tissue randomly. Xylem’s part- Tracheid,vessel,xylem parenchyma and xylem fibre.

Phloem’s part – sieve tube,companion cell,phloem parenchyma and phloem fibre

Ground Tissue

Ground tissue comprises parenchyma cells, but it can also contain sclerenchyma cells and collenchyma cells, which help maintain stem cells. The pith is the tissue layer between the circulatory tissue and the epidermis in a stem or root. In contrast, the cortex is the tissue layer between the vascular tissue and the epidermis.

The internal and external anatomy of the monocot and dicot stem is followed.

Anatomy of Monocot Stems

Monocot stems, such as corn, palms and bamboos, lack a vascular cambium and do not produce concentric yearly rings as a means of secondary development. Conifers and woody dicots can extend their girth by adding lateral layers of cells, but they can’t. Instead, they have circulatory bundles made up of xylem and phloem tissue that are sprinkled throughout. The internal structure of the stem and their functions are followed. A bundle sheath is a ring of cells that surrounds each bundle. Clusters of strongly lignified tracheids and fibers connected with the vascular bundles provide woody monocots with structural strength and hardness.

Anatomy of Dicot Stems

Vascular bundles are organized in a ring around the pith in the Dicot Stem. There are four types of vascular bundles: conjoint, collateral, open and endarch. Dicotyledonous stems or dicot stems have two cotyledons or embryonic leaves. There are no intercellular spaces in the epidermis, a single layer of parenchymatous cells that protects the skin. The epidermal cells feature a coating called cuticle on their exterior walls and multicellular hairs (trichomes). Cortex differentiates into a few layers of collenchyma cells beneath the epidermis, forming the hypodermis, providing the stem’s mechanical strength. A few layers of chlorenchyma cells have intercellular gaps evident. Resin ducts can be found here as well. Parenchyma cells make up the third zone. Food materials are stored in these cells. Finally, the endodermis has barrel-shaped cells packed tightly together with no intercellular gaps. This layer is also known as the starch sheath because of the abundance of starch granules in these cells.

Conclusion

In this article, we read about the stem’s anatomy and the types of cells and tissues in the stem. Also, we gained information about the internal and external anatomy of monocot and dicot stems.