what are the major type of plant tissues?

Answer 1

Tissue types

1. Parenchyma

Parenchyma cells are the progenitor of all other cells and the most common component of ground tissues. They perform virtually all the metabolic activities of plant cells.

Parenchyma cells are living at maturity. Their shape is described as polyhedral (many sided). They are capable of cell division. In the primary plant body they occur as continuous masses in roots, stems, and leaves, often with prominent air spaces between the cells. They may also occur as vertical strands of cells in vascular tissues and also as horizontal strands (rays) in secondary vascular tissues. Some may have secondary walls. Those with only primary walls play an important role in regeneration and wound healing. They may be lignified, suberized or cutinized.

There are several different types of parenchyma cells, categorized by function. For example, chlorenchyma cells contain chloroplasts and are specialized for photosynthesis. Aerenchyma cells contain large intracellular air spaces and function in gas exchange.

2. Collenchyma

Collenchyma cells are living at maturity, like parenchyma. They usually occur as discrete strands or as continuous cylinders beneath the epidermis in stems and petioles (e.g. celery). They also border veins in dicots. Collenchyma cells are relatively long, with nonlignified primary walls which allows them to stretch. They are distinguished from parenchyma cells by their unevenly thickened cell walls. The function of collenchyma is to provide support for the primary plant body.

3. Sclerenchyma

Sclerenchyma cells are non-living and lack protoplasts at maturity. They may be found in all parts of both the primary and secondary plant body. They have thick, lignified secondary walls. They provide strength and support in parts that have ceased elongating. There are two type of sclerenchyma cells:

A. Fibers - long slender cells which occur in strands or bundles, e.g. hemp, flax and jute. Fibers have very thin lumens, the space left after the protoplast decays. Fibers provide support for the plant.

B. Sclereids - vary in shape, often branched, may occur singly or in groups in ground tissues throughout the plant. They make up the seed coat of seeds, shells of nuts, stones of drupes, and give the pear its gritty texture. Their function is primarily for protection.

4. Epidermis

The epidermis is the outermost layer of the primary plant body. It covers leaves, floral parts, fruits, seeds, stems and roots. In organs that undergo secondary growth, the epidermis is eventually replaced by the periderm.

The epidermis is generally only one layer thick and is composed mostly of unspecialized cells, either parenchyma and/or sclerenchyma. The majority of epidermal do not contain chloroplasts, although guard cells are an important exception. Epidermal cells also secrete a waxy substance called cutin over their exterior suface to form a protective covering called the cuticle which prevents desiccation.

In leaves and stems the epidermis contains several types of specialized cells:

Guard cells are sausage-shaped cells that occur in pairs on leaf surfaces. They form pores called stomata that regulate the entry and exit of gases such as carbon dioxide, oxygen, and water vapor.


Trichomes are hair-like projections. They may be either unicellular or multicellular. Glandular trichomes secrete certain substances. Root hairs are the major site of absorption in the soil.


Gland cells secrete chemicals and salts.

5. Periderm

The periderm replaces the epidermis in stems and roots that undergo secondary growth. It is commonly composed of parenchyma and sclerenchyma cells, as well as cork and phelloderm.

6. Xylem

Xylem is a complex tissue and one of the major components of the vascular tissue system. It is the principle water conducting tissue in vascular plants. Xylem is produced during both primary and secondary growth. The principal conducting cells are called tracheary elements, hollow elongated cells with thickened secondary walls that are dead at maturity. Other cell types found in xylem are parenchyma and sclerenchyma fibers.

There are two types of tracheary elements:

Tracheids - generally long and thin with tapered ends. They contain pits in their walls through which water and nutrients can move. However, they have imperforate (closed) end walls. Tracheids are the only type of tracheary element found in the seedless vascular plants such as ferns and gymnosperms (primitive seed plants).

Vessel elements - elongated shape but not as long or thin as tracheids. They have perforate (open) end walls. Vessel members are joined together end-to-end in long tubes called vessels. Vessels are generally wider than tracheids and therefore permit faster flow through the xylem.


7. Phloem

The phloem is another complex tissue that is associated with xylem in the vascular bundles. It is the principle food conducting tissue in vascular plants and consists of elongated cells called sieve elements that join end-to-end to form sieve tubes. These are narrower than the vessel elements of the xylem.

Unlike tracheary elements, sieve elements are living at maturity, but they typically lack nuclei or other organelles. At maturity the tonoplast of the vacuole disappears so that there is no differentiation between the cytoplasmic and vacuolar contents. The remaining elements of the protoplast (plasma membrane, plastids, smooth ER, mitochondria) are distributed along the cell walls. There are no ribosomes, dictyosomes, or nuclei.

There are differences in the structure of the phloem between angiosperms (flowering plants) and other groups of vascular plants. In angiosperms the sieve elements, called sieve tube members, are joined at their ends by structures known as sieve plates. The protoplasts of adjacent sieve tube elements are interconnected through the sieve plates. Sieve tube members are usually associated with specialized parenchyma cells called companion cells. These are complete living cells connected to sieve tube members by numerous plasmodesmata. The companion cells maintain the seive tube members and perform many of their metabolic activities.

In gymnosperms and most seedless vascular plants (e.g., ferns), the sieve elements, called sieve cells have narrow pores and lack sieve plates. They are often accompanied by albuminous cells which serve the same function as companion cells, but do not develop from the same progenitor cell.

Answer 2

There are two major divisions of plant tissues:

I The meristematic tissues that are capable of active cell division (embryonic) which are generally found at the tips of roots and stems.

II The permanent tissues that are subdivided into three, namely:

1) Fundamental tissues (ground tissues) - parenchyma, collenchyma, sclerechyma and endodermis;

2) Vascular tissues - xylem and phloem; and

3) Surface tissues - the epidermis and periderm.

Answer 3

be it leaf stem or root each thee tissue systems. dermal,vascular and ground tissue systems.

dermal--(epidermis)--is generally a single layer of tightly packed cells...there is also the cuticle

vascular tissue are of two types the xylem and phloem...the xylem has tracheids and vessel elements

ground tissue is divided into the pith and cortex

Answer 4

visit http://www.estrellamountain.edu/faculty/farabee/biobk/BioBookPLANTANAT.html