Plant Tissue Types and Their Functions

Parenchyma

They are essential for activities like photosynthesis, storage, gas exchange, and protection.

Collenchyma

Elongated cells with thickened cell walls that provide structure and support for plants. Provide flexibility for plants as well as tissue repair and replacement.

Sclerenchyma

Thickened lignified walls which make them strong and waterproof. Supports more mature plants.

Meristematic tissue

Undifferentiated embryonic plant tissue from which all other plant tissue develops.

Palisade parenchyma

Contains the largest number of chloroplasts per cell and is the primary site of photosynthesis in many plants.

Spongy parenchyma

A layer of loosely arranged, irregularly shaped cells found in the interior of leaves, beneath the palisade parenchyma. It's characterized by large air spaces between the cells, which facilitate gas exchange.

Lignin

A complex organic polymer deposited in the cell walls of many plants, making them rigid and woody.

Dermal tissue

Forms the outer covering of the plant; it includes epidermis and periderm. The outer layer that forms a protecting covering for the plant.

Epidermis

The dermal tissue is a single layer that makes up the plant's protective outer covering. Older plants form dermal tissue like periderm, which is produced as part of secondary growth. It replaces the epidermis to form cork in woody stems and roots.

Cuticle

A waxy, protective film covering the outermost layer of aerial plant parts like leaves and young shoots. An extracellular hydrophobic layer that covers the aerial epidermis of all land plants.

Guard cells

Paired cells that, together, surround a stoma (plural stomata). Stomata are small openings or pores, usually in the leaves. Guard cells control the size of the stomata. When stomata are open, gas exchange can occur. During the day, carbon dioxide diffuses in through the stomata and oxygen diffuses out.

Stoma

A small opening, usually in the leaf, that allows gas exchange to occur.

Pavement cells

The most common type of epidermal layer in plants forms a protective layer on the leaf's surface.

Subsidiary cells

They are specialized epidermal cells that surround and support the guard cell in the plant's stoma.

Ground tissue

A plant tissue that has multiple functions and makes up most of the inside of the plant. It forms most of the plant's internal and external material. Contains: parenchyma cells, collenchyma cells, and sclerenchyma cells.

Xylem

Vascular tissue that transports water and minerals from the roots to the leaves. It contains two types of cells: tracheids and vessel elements.

Phloem

Vascular tissue that transports organic nutrients, often from the leaves to the roots and mature leaves to new leaves. They have two types of phloem cells: sieve tube elements and companion cells.

Tracheids

Elongated tube-like structures with tapering ends that conduct water and minerals in both gymnosperms and some angiosperms.

Vessel elements

Longer, more specialized water-conducting cells found primarily in angiosperms.

Sieve tube elements

Generally long, narrow, and tapered at the ends, whereas sieve tubes are shorter, wider, with more horizontal end walls.

Companion cells

Support sieve tube elements in the phloem by providing metabolic support, specifically by loading and unloading sugars like sucrose.

Cortex

A layer of cells between the epidermis and the vascular tissues of the root, composed of ground tissue made of parenchyma cells that transport and store water, minerals, and food in the plant.

Endodermis

A layer on the inside edge of the cortex, between the cortex and the vascular tissue, that is one cell thick and surrounded by a waterproof band called a Casparian strip.

Casparian strip

Creates a barrier that forces water and dissolved minerals to cross the plasma membrane and pass through the cytoplasm of endodermal cells, allowing only water and certain dissolved nutrients and ions to enter the vascular system.

Mesophyll

The tissue between the upper and lower epidermis of the leaf, made up of parenchyma containing numerous chloroplasts.

Apical meristem

Regions of undifferentiated cells at the tips of plants and shoots, responsible for primary growth, including the extension of the plant length.

Intercalary meristem

Tissues found along the stems and at the base of the leaf blades of some vascular plants, enabling plant growth in length, particularly in monocots like grasses.

Lateral meristem

Cells found at the margins of stems and roots, responsible for growth in diameter in plants, a process known as secondary growth.

Vascular cambium

Responsible for producing secondary xylem and phloem that are formed in stems and roots after the tissues of the primary plant body have differentiated.

Cork Cambium

A lateral meristematic tissue in plants that produces the outer bark, or periderm, found between the cork and the primary phloem within the bark.

Periderm

A protective outer layer of plant tissue that replaces the epidermis in stems and roots, particularly in woody plants during secondary growth.

Primary growth

The cells produced from meristems cause roots, stems, and leaves to grow longer throughout the life of the plant.

Secondary growth

Refers to the thickening or increase in girth of stems and roots, primarily driven by lateral meristems called the vascular cambium and cork cambium.