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Plant Hormones (Phytohormones) or Plant Growth regulators

PLANT HORMONES - Teachoo.jpg

  • As we discussed in the case of animals, plants also have hormones.
  • Hormones are chemical messengers that respond to internal and external stimuli.
  • They are produced in small quantities in a part of t he plant and then t ransported through xylem, phloem or by diffusion to other parts.
  • They may promote or inhibit growth.

 

Plant growth promoters

1. Auxins

Let us consider the example of a sunflower growing towards the sunlight.

  • Once the plant detects sunlight , the hormone auxin is secreted at the shoot tips .
  • The secreted auxins diffuse towards the shady side of the plant
  • This makes the cells on the shady side grow longer
  • Thus, the plant appears to bend towards light

AUXIN AND PHOTOTROPISM - Teachoo.jpg

2. Gibberellins

Gibberellins also help in growth

Gibberellins in contrast to auxins help in growth of stem

GIBBERELLINS - STEM GROWTH - Teachoo.jpg

3.  Cytokinin's

Cytokinin's   play an important role in cell division

They promote cell division

Usually they are present in greater concentrations in fruits and se eds.

The rate of cell division in the plant is higher in the region that has higher concentrations of cytokinins.

This simple means;

FUNCTION OF CYTOKININS - Teachoo.jpg

Plant growth inhibitors

4. Abscisic acid

Abscisic acid is different from other plant growth regulators as the others are responsible for promoting growth, bu t Abscisic acid stops growth.

  • Wilting and yellowing of leaves is an example of the effect of Abscisic acid.

EFFECT OF ABSCISIC ACID IN PLANTS - Teachoo.jpg

5. Ethylene

When you go to the fruit shop, have you noticed that mangoes are kept wrapped in paper bags? Why is this done?

  • Mangoes wrapped in a paper bag will release ethylene .

MANGO RIPENING DUE TO ETHYLENE - Teachoo.jpg

  • Ethylene is an odorless gas.It speeds up the ripening process and is also involved in production of more flowers and fruits.
  • Ethylene comes under plant growth inhibitors as the process of growth is stopped and focuses on production and ripening of flowers and fruits. 

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Transcript

GIBBERELLINS - STEM GROWTH EFFECT OF ABSCISIC ACID IN PLANTS Auxin Auxin Ethylene Ethylene Yellow MANGO RIPENING DUE TO ETHYLENE FUNCTION OF CYTOKININS ( PLANT HORMONE) Cytokinins = More Mitosis More Mitosis = More Cells More Cells = Plant Growth AUXIN AND PHOTOTROPISM

Maninder Singh's photo - Co-founder, Teachoo

Made by

Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 12 years and a teacher from the past 16 years. He teaches Science, Economics, Accounting and English at Teachoo