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Plant tissues and Hormones

In this article we will discuss about the plant tissues and hormones. Question from this section are important for competitive exam. This  topic are also useful for the upcoming SSC CGL Exam.

Plant Tissue

 Tissue : The group of cells of similar origin, structure and functions is called tissue.
 Types of Plant Tissue :
(A) Meristematic tissue :
Meristematic tissues are those tissues in which the cells remain forever young and divide actively throughout the life of the plant.
Some features of  Meristematic tissues are as follows :
  • It is round, oval or multi-sided.
  •  Its wall is thin and cytoplasm is homogeneous.
  • Cell contains dense cytoplasm and a single large nucleus.
  • There is lack of inter-cellular spaces between the cells.
  • Apical Meristems : These tissues are found in the root and stem apex and the initial growth (specially length) of the plants take place due to these tissue.
  • Lateral Meristems : Due to the division in these tissue growth in the girth of roots and stems takes place. Hence, it increases the width of the root and stem.
  • Intercalary Meristems : They are located at the base of internode. In fact, this is the remains of the Apical Meristems, which is divided by the incoming of permanent tissues in the centre. Plants increase its length by the activity of this. 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 :
Meristematic tissues after cell division and differentiation produce permanent tissue.

Permanent tissues are of following types
Simple tissue:
If permanent tissue is made up of similar types of cells, it is called simple tissue.
Complex tissue :
If permanent tissue is made up of one or more types of cells, it is called
Complex tissue.

Complex tissues are of two types
Xylem :
Xylem is a conducting tissues. Its main functions are –
  • Conduction of water and minerals and
  •  To provide mechanical consistency.
Phloem : This is a conducting tissue. Its main function is to conduct foods prepared by the leaves to different parts of the plant.

Plant Hormones:

Following  hormones are found in plants –
Auxins :
Auxins was discovered by Darwin in the year 1880.
This is the hormone which controls the growth of plants.
Its formation takes place in the apex parts of the plants.
Its main functions are –
(i) It prevents the separation of the leaves.
(ii)  It destroys the straws.
(iii) It saves the crops from falling.
Gibberellins :
It was discovered by a Japanese scientist Kurosava in the year 1926.
Its main function are as follows :
  • It turns the dwarf plants into long plants.
  • It helps in creating flowering.
  •  It hep in breaking the dormancy of plant.
  • It motivates the seeds to be sprout.
  • It increases the activity of cambium in the wooden plants.
  •  Large sized fruits and flowers can be produced by its scattering.
Cytokinins :
It was discovered by z in the year 1955 but it was named by Lethem.
Its main function are as follows:
  •  It naturally works in coordination with auxins.
  • It help in cell division and development in the presence of auxins.
  •    It help in breaking the dormancy of seed.
  • It is helpful in making RNA and protein.
Abscisic Acid or ABA :
This hormone was initially discovered by Carnes and Adicote and later on by Waring.
Its main function are as follows:
  • This hormone is against the growth.
  •  It keeps the seeds & bud in dormant condition.
  • It plays main role in separation of leaves.
  •  It delays in flowering of long day plant.
Ethylene :
This is the only hormone which is found in gaseous form.
Its main functions are as follows:
  • It helps in the ripening the fruits.
  •  It increases the number of female flowers.
  • It motivates the separation of leaves, flowers and fruits.
Florigens :
  • It is formed in leaves but helps in blooming of the flowers.
  • It is also called flowering hormones
Traumatic :
  • This is a type of dicarboxylic acid.
  • It is formed in injured cells by which the injury of plants is healed.