Plant Tissue Systems

Plant Vascular Tissue — Magda Turzanska/Science Photo Library/Getty Images

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Updated on January 21, 2020

Like other organisms, plant cells are grouped together into various tissues. These tissues can be simple, consisting of a single cell type, or complex, consisting of more than one cell type. Above and beyond tissues, plants also have a higher level of the structure called plant tissue systems. There are three types of plant tissue systems: dermal tissue, vascular tissue, and ground tissue systems.

Dermal Tissue

Tree Bark — Elizabeth Fernandez/Moment/Getty Images

The dermal tissue system consists of the epidermis and the periderm. The epidermis is generally a single layer of closely packed cells. It both covers and protects the plant. It can be thought of as the plant's "skin." Depending on the part of the plant that it covers, the dermal tissue system can be specialized to a certain extent. For instance, the epidermis of a plant's leaves secretes a coating called the cuticle that helps the plant retain water. The epidermis in plant leaves and stems also contain pores called stomata. Guard cells in the epidermis regulate gas exchange between the plant and the environment by controlling the size of the stomata openings.

The periderm, also called bark, replaces the epidermis in plants that undergo secondary growth. The periderm is multilayered as opposed to the single-layered epidermis. It consists of cork cells (phellem), phelloderm, and phellogen (cork cambium). Cork cells are nonliving cells that cover the outside of stems and roots to protect and provide insulation for the plant. The periderm protects the plant from pathogens, injury, prevents excessive water loss, and insulates the plant.

Key Takeaways: Plant Tissue Systems

Plant cells form plant tissue systems that support and protect a plant. There are three types of tissue systems: dermal, vascular, and ground.
Dermal tissue is composed of epidermis and periderm. Epidermis is a thin cell layer that covers and protects underlying cells. The outer periderm, or bark, is a thick layer of nonliving cork cells.
Vascular tissue is composed of xylem and phloem. These tube-like structures transport water and nutrients throughout the plant.
Ground tissue generates and stores plant nutrients. This tissue is composed mainly of parenchyma cells and also contains collenchyma and sclerenchyma cells.
Plant growth occurs in areas called meristems. Primary growth occurs at apical meristems.

Vascular Tissue System

Xylem and Phloem in Dicotyledon plant — The center of this stem is filled with large xylem vessels for transporting water and mineral nutrients from the roots to the main body of the plant. Five bundles of phloem tissue (pale green) serve to distribute carbohydrate and plant hormones around the plant. Steve Gschmeissner/Science Photo Library/Getty Images

Xylem and phloem throughout the plant make up the vascular tissue system. They allow water and other nutrients to be transported throughout the plant. Xylem is consists of two types of cells known as tracheids and vessel elements. Tracheids and vessel elements form tube-shaped structures that provide pathways for water and minerals to travel from the roots to the leaves. While tracheids are found in all vascular plants, vessels are found only in angiosperms.

Phloem is composed mostly of cells called sieve-tube cells and companion cells. These cells assist in the transport of sugar and nutrients produced during photosynthesis from the leaves to other parts of the plant. While tracheid cells are nonliving, sieve-tube and companion cells of the phloem are living. Companion cells possess a nucleus and actively transport sugar into and out of sieve-tubes.

Ground Tissue

Plant Cell Types — Kelvinsong/Creative Commons Attribution 3.0 Unported

The ground tissue system synthesizes organic compounds, supports the plant, and provides storage for the plant. It is mostly made up of plant cells called parenchyma cells but can also include some collenchyma and sclerenchyma cells as well. Parenchyma cells synthesize and store organic products in a plant. Most of the plant's metabolism takes place in these cells. Parenchyma cells in leaves control photosynthesis. Collenchyma cells have a support function in plants, particularly in young plants. These cells help to support plants while not restraining growth due to their lack of secondary cell walls and the absence of a hardening agent in their primary cell walls. Sclerenchyma cells also have a support function in plants, but unlike collenchyma cells, they have a hardening agent and are much more rigid.

Plant Tissue Systems: Plant Growth

Apical Meristem — This is a light micrograph of the growing tip (apical meristem) of a corn plant root. Garry DeLong/Oxford Scientific/Getty Images

Areas within a plant that is capable of growth via mitosis are called meristems. Plants undergo two types of growth, primary and/or secondary growth. In primary growth, plant stems and roots elongate by cell enlargement as opposed to new cell production. Primary growth occurs in areas called apical meristems. This type of growth allows plants to increase in length and to extend roots deeper into the soil. All plants undergo primary growth. Plants that undergo secondary growth, such as trees, have lateral meristems that produce new cells. These new cells increase the thickness of stems and roots. Lateral meristems consist of the vascular cambium and the cork cambium. It is the vascular cambium that is responsible for producing xylem and phloem cells. The cork cambium is formed in mature plants and yields bark.