In this article, we will discuss various plant tissues and their functions. Questions from this chapter are crucial for competitive exams. This topic is also useful for the Railway Exams primarily conducted for recruiting candidates into various positions in Indian Railways..
Plant Tissues :
Tissue: is an intermediate substance between cell and organ. The group of cells of similar origin, structure and functions is called tissue. Types of Plant Tissues are as below:
(A) Meristematic tissue:

• Meristematic tissues give rise to various organs and help plants to grow.


• Meristematic tissues are those tissues in which the cells remain forever young and divide actively throughout the life of the plant.


• These tissues have the capability of the cell division

Some features of Meristematic tissues are as follows :

• It is round, oval or multi-sided


• The cell wall is a very thin primary cell wall and cytoplasm is homogeneous


• Cell contains dense cytoplasm and a single large nucleus.


• There is lack of inter-cellular spaces between the cells.


• Maintenance of the cells requires a balance between two antagonistic processes: organ initiation and stem cell population renewal.

Apical Meristems:

• Found in the root and stem apex.


• Produces auxin and causes the root to increase its length.

Lateral Meristems:

• There is two type of secondary meristems which are also called as lateral meristems because they surround the plant stem and cause to grow them laterally.

Intercalary Meristems:

• Located at the base of the internode.


• It is capable of cell division and allows for rapid growth and regrowth of many monocots.


• Its importance is for those plants whose apex parts are eaten by vegetarian animals. After being eaten the apex part the plants grow with the help of intercalary meristems only. Like – grass.

(B) Permanent tissue:

• These are made of those mature tissues that have lost their capacity of the division. And attain a denite form for various works.

Permanent tissues are of following types
Type of Complex Tissues

• Xylem and phloem are the complex tissues which constitute the component parts of the vascular bundle. They are also called vascular tissues.

Xylem:

• Xylem is a complex tissue forming part of a vascular bundle.

Its main functions are:

• Conduction of water and minerals


• Provide mechanical support.

Dendrochronology: Determination of age of the plant is done by counting annual rings of the xylem tissue.
Phloem:

• It is composed of sieve elements, companion cells, parenchyma and some bres.

Its main function is to conduct foods prepared by the leaves to different parts of the plant.

Plant Hormones and their functions:
Following hormones are found in plants –
Auxins:

• Discovered by Darwin in the year 1880.


• Controls the growth of plants.


• They are produced in the stem, buds, and root tips.

Its main functions are :

• Enhance stem growth and growth of lateral buds.


• Auxin also plays a role in maintaining apical dominance.


• Prevents the separation of the leaves.


• It saves the crops from falling and It destroys the straws.

Gibberellins:

• Discovered by a Japanese scientist Kurosawa in the year 1926.

Its main functions are:

• Promotes stem elongation.


• Motivates the seeds to be sprout.


• Increases the activity of cambium in the wooden plants.


• Turns the dwarf plants into long plants. And also.


• Helps in breaking the dormancy of plant.


• Helps in creating owering, Large sized fruits and owers can be produced by its scattering.

Cytokinins:

• Discovered by Miller in the year 1955 but it was named by Lethem.


• Its main functions are


• Promotes cell division and development in the presence of auxins.


• Naturally works in coordination with auxins.


• Helps in breaking the dormancy of seed.


• Enhance RNA and protein synthesis.

Abscisic Acid or ABA:

• Initially discovered by Carnes and Adicote and later on by Waring.


• Abscisic acid is also produced in the roots in response to decreased soil water potential and other situations in which the plant may be under stress.


• Its main functions are-


• This hormone is against the growth.


• Keeps the seeds & bud in the dormant condition.


• Plays the main role in the separation of leaves.


• Delays in the owering of long day plant.

Ethylene:

• The only hormone which is found in the gaseous form.


• Its main functions are-


• Helps in the ripening of fruit, the opening of owers, and the abscission (or shedding) of leaves.


• It increases the number of female owers.


• Motivates separation of leaves, owers and fruits.

Florigens:

• Formed in leaves but helps in controlling a oirntar pigpgering or blooming of owers in plants.


• Also called owering hormones.

Traumatic:

• Helps in xing the injuries of plants.

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