Leaves consist of what kind of tissue

This meristem will also actively produce new cells and is responsible for increases in length. The intercalary meristem is responsible for the regrowth of cut grass.

There are other tissues in plants that do not actively produce new cells. These tissues are called nonmeristematic tissues. Nonmeristematic tissues are made of cells that are produced by the meristems and are formed to various shapes and sizes depending on their intended function in the plant.

Sometimes the tissues are composed of the same type of cells throughout, or sometimes they are mixed. There are simple tissues and complex tissues to consider but we will start with the simple tissues for the sake of discussion.

There are three basic types named for the type of cell that makes up their composition: 1 parenchyma tissue , 2 collenchyma tissue , and 3 sclerenchyma tissue. Parenchyma cells form parenchyma tissue.

Parenchyma cells are the most abundant of cell types and are found in almost all major parts of higher plants. These cells are basically sphere-shaped when they are first made. However, these cells have thin walls, which flatten at the points of contact when many cells are packed together. Generally, they have many sides with the majority having 14 sides. These cells have large vacuoles and may contain various secretions including starch, oils, tannins, and crystals.

Some parenchyma cells have many chloroplasts and form the tissues found in leaves. This type of tissue is called chlorenchyma. The chief function of this type of tissue is photosynthesis, while parenchyma tissues without chloroplasts are generally used for food or water storage. Additionally, some groups of cells are loosely packed together with connected air spaces, such as in water lilies, this tissue is called aerenchyma tissue.

These types of cells can also develop irregular extensions of the inner wall which increases the overall surface area of the plasma membrane and facilitates transferring of dissolved substances between adjacent cells.

Parenchyma cells can divide if they are mature, and this is vital in repairing damage to plant tissues. Parenchyma cells and tissues comprise most of the edible portions of fruit.

Collenchyma cells form collenchyma tissue. These cells have a living protoplasm, like parenchyma cells, and may also stay alive for a long period of time. Their main distinguishing difference from parenchyma cells is the increased thickness of their walls.

In cross-section, the walls look uneven. Collenchyma cells are found just beneath the epidermis and generally, they are elongated and their walls are pliable in addition to being strong. As a plant grows these cells and the tissues they form, provide flexible support for organs such as leaves and flower parts. Sclerenchyma cells form sclerenchyma tissue.

These cells have thick, tough secondary walls that are embedded with lignin. At maturity, most sclerenchyma cells are dead and function in structure and support. Sclerenchyma cells can occur in two forms:. As a result of cellular processes, substances that are left to accumulate within the cell can sometimes damage the protoplasm. Thus it is essential that these materials are either isolated from the protoplasm in which they originate, or be moved outside the plant body.

Although most of these substances are waste products, some substances are vital to normal plant functions. Examples: oils in citrus, pine resin, latex, opium, nectar, perfumes, and plant hormones.

Generally, secretory cells are derived from parenchyma cells and may function on their own or as a tissue. They sometimes have great commercial value. Tissues composed of more than one cell type are generically referred to as complex tissues. Xylem and phloem are the two most important complex tissues in a plant, as their primary functions include the transport of water, ions, and soluble food substances throughout the plant. While some complex tissues are produced by apical meristems, most in woody plants are produced by the vascular cambium and is often referenced as vascular tissue.

Other complex tissues include the epidermis and the periderm. The epidermis consists primarily of parenchyma-like cells and forms a protective covering for all plant organs. Unlike the animal circulatory system, where the vascular system is composed of tubes that are lined by a layer of cells, the vascular system in plants is made of cells — the substance water or sugars actually moves through individual cells to get from one end of the plant to the other. Xylem tissue transports water and nutrients from the roots to different parts of the plant, and includes vessel elements and tracheids , both of which are tubular, elongated cells that conduct water.

Tracheids are found in all types of vascular plants, but only angiosperms and a few other specific plants have vessel elements. Tracheids and vessel elements are arranged end-to-end, with perforations called pits between adjacent cells to allow free flow of water from one cell to the next. They have secondary cell walls hardened with lignin , and provide structural support to the plant. Tracheids and vessel elements are both dead at functional maturity, meaning that they are actually dead when they carry out their job of transporting water throughout the plant body.

Phloem tissue, which transports organic compounds from the site of photosynthesis to other parts of the plant, consists of sieve cells and companion cells.

Sieve cells conduct sugars and other organic compounds, and are arranged end-to-end with pores called sieve plates between them to allow movement between cells. They are alive at functional maturity, but lack a nucleus, ribosomes, or other cellular structures. Sieve cells are thus supported by companion cells, which lie adjacent to the sieve cells and provide metabolic support and regulation. The xylem and phloem are always next to each other. In stems, the xylem and the phloem form a structure called a vascular bundle ; in roots, this is termed the vascular stele or vascular cylinder.

This light micrograph shows a cross section of a squash Curcurbita maxima stem. Each teardrop-shaped vascular bundle consists of large xylem vessels toward the inside and smaller phloem cells toward the outside.

Xylem cells, which transport water and nutrients from the roots to the rest of the plant, are dead at functional maturity. Phloem cells, which transport sugars and other organic compounds from photosynthetic tissue to the rest of the plant, are living. The vascular bundles are encased in ground tissue and surrounded by dermal tissue. Ground tissue cells include parenchyma, photosynthesis in the leaves, and storage in the roots , collenchyma shoot support in areas of active growth , and schlerenchyma shoot support in areas where growth has ceased.

Parenchyma are the most abundant and versatile cell type in plants. They have primary cell walls which are thin and flexible, and most lack a secondary cell wall.

Parenchyma cells are totipotent, meaning they can divide and differentiate into all cell types of the plant, and are the cells responsible for rooting a cut stem. Most of the tissue in leaves is comprised of parenchyma cells, which are the sites of photosynthesis, and parenchyma cells in the leaves contain large quantities of chloroplasts for phytosynthesis. In roots, parenchyma are sites of sugar or starch storage, and are called pith in the root center or cortex in the root periphery.

Parenchyma can also be associated with phloem cells in vascular tissue as parenchyma rays. Collenchyma , like parenchyma, lack secondary cell walls but have thicker primary cells walls than parenchyma. They are long and thin cells that retain the ability to stretch and elongate; this feature helps them provide structural support in growing regions of the shoot system. They are highly abundant in elongating stems.

Schlerenchyma cells have secondary cell walls composed of lignin , a tough substance that is the primary component of wood. Schelrenchyma cells therefore cannot stretch, and they provide important structural support in mature stems after growth has ceased. Interestingly, schlerenchyma cells are dead at functional maturity. Schlerenchyma give pears their gritty texture, and are also part of apple cores. We use sclerenchyma fibers to make linen and rope. This waxy region, known as the Casparian strip, forces water and solutes to cross the plasma membranes of endodermal cells instead of slipping between the cells.

A cross section of a leaf showing the phloem, xylem, sclerenchyma and collenchyma, and mesophyll. Each plant organ contains all three tissue types, with different arrangements in each organ. There are also some differences in how these tissues are arranged between monocots and dicots, as illustrated below:.

In dicot roots, the xylem and phloem of the stele are arranged alternately in an X shape, whereas in monocot roots, the vascular tissue is arranged in a ring around the pith. In addition, monocots tend to have fibrous roots while eudicots tend to have a tap root both illustrated above. In left typical dicots, the vascular tissue forms an X shape in the center of the root. In right typical monocots, the phloem cells and the larger xylem cells form a characteristic ring around the central pith.

The cross section of a dicot root has an X-shaped structure at its center. The X is made up of many xylem cells. Phloem cells fill the space between the X. A ring of cells called the pericycle surrounds the xylem and phloem. In plants with stems that live for more than one year, the individual bundles grow together and produce the characteristic growth rings.

In monocot stems, the vascular bundles are randomly scattered throughout the ground tissue Figure 3. Figure 3. In a dicot stems, vascular bundles are arranged around the periphery of the ground tissue.

The xylem tissue is located toward the interior of the vascular bundle, and phloem is located toward the exterior. Sclerenchyma fibers cap the vascular bundles. In b monocot stems, vascular bundles composed of xylem and phloem tissues are scattered throughout the ground tissue.

Xylem tissue has three types of cells: xylem parenchyma, tracheids, and vessel elements. The latter two types conduct water and are dead at maturity. Tracheids are xylem cells with thick secondary cell walls that are lignified. Water moves from one tracheid to another through regions on the side walls known as pits, where secondary walls are absent. Vessel elements are xylem cells with thinner walls; they are shorter than tracheids.

Each vessel element is connected to the next by means of a perforation plate at the end walls of the element. Water moves through the perforation plates to travel up the plant. Phloem tissue is composed of sieve-tube cells, companion cells, phloem parenchyma, and phloem fibers. A series of sieve-tube cells also called sieve-tube elements are arranged end to end to make up a long sieve tube, which transports organic substances such as sugars and amino acids.

The sugars flow from one sieve-tube cell to the next through perforated sieve plates, which are found at the end junctions between two cells. Although still alive at maturity, the nucleus and other cell components of the sieve-tube cells have disintegrated. Companion cells are found alongside the sieve-tube cells, providing them with metabolic support. The companion cells contain more ribosomes and mitochondria than the sieve-tube cells, which lack some cellular organelles.

Ground tissue is mostly made up of parenchyma cells, but may also contain collenchyma and sclerenchyma cells that help support the stem.

The ground tissue towards the interior of the vascular tissue in a stem or root is known as pith , while the layer of tissue between the vascular tissue and the epidermis is known as the cortex. Figure 1. What is this abstract pattern? Is it just a random artistic piece? Is it a depiction of a pattern of bubbles? Would you believe it is part of a plant?

It is actually the center portion of a carrot taproot. And these are all cells. Cells that have come together to form a tissue, with a specific function.

As for all animals, your body is made of four types of tissue: epidermal, muscle, nerve, and connective tissues.