Topic discussed here is the Chemical Coordination in plants, the various hormones that are found in plants & their function

1. CHEMICAL COORDINATION IN
PLANTS
CONTROL & COORDINATION-III

3. WHAT ARE PLANT
HORMONES?
 Plant hormones are
chemicals in plants
that regulate cellular
processes.
 They are usually
found in small
amounts throughout
the plant.
 Plant hormones are
also known as
phytohormones.
TGES

4. PLANT HORMONES
Auxins
Gibberelins
Cytokinins
Ethylene
Abscisic acid
Auxins
Gibberelins
Cytokinins
Ethylene
Abscisic acid
Auxins
Gibberelins
Cytokinins
Ethylene
Abscisic acid
Auxins
Gibberelins
Cytokinins
Ethylene
Abscisic acid
Auxins
Gibberelins
Cytokinins
Ethylene
Abscisic acid

6. AUXINS
 Greek ‘auxein’ : to grow
 Coined by F.W. Went 1928
 Auxin promotes plant growth by
facilitating the elongation of developing
cells.
 IAA (Indole 3-acetic acid) is the natural
auxin found in plants
 Auxin is produced at the tips of roots and
shoots.
 Along with other hormones, auxin
influences plant responses to light
(phototropism) and gravity (geotropism)

7. AUXINS
 Phototropism experiments by Charles and his
son Francis Darwin:
Shoot with opaque cap does not bend towards light,
they concluded that the tip had some chemicals that
communicated to other parts of the stem.

8. AUXINS
 Promoting apical dominance
(apical buds over lateral buds)
 Auxins delay falling of leaves
 Auxins induce fruit formation
without fertilization in fruits
like apple, tomato, banana.
 Development of fruits without
fertilization is called
Parthenocarpy

9. LATERAL ROOT ELONGATION INDUCED
BY AUXINS

11. PLANT HORMONES
Auxins
Gibberelins
Cytokinins
Ethylene
Abscisic acid
lins

12. GIBBERELLINS
GA 3 STRUCTURE NOT
REQUIRED TO
MEMORIZE
TYPES OF GIBBERELLINS
 GA1, GA2, GA3 AND SO ON…
 GA3 is the most studied form
Distribution – In higher plants they are mainly distributed
in the meristematic regions like stem-apex, root-apex,
buds, seeds, etc.
Function
 Their main function is to promote the growth of
internodes by cell elongation,
 Promote fruit growth,
 Break seed dormancy, and initiate germination.
 They also delay senescence (ageing)

13. GIBBERELLINS
 Applications
1. Horticulture
2. Food industry
3. Increase length of grapes
4. Elongate apple size and improve shape
5. Gibberellic acid is used to speed up the
malting process in brewing industry.

14. GIBBERELLINS
Thompson seedless grapes
Without GA With GA
Larger fruits that are easier to clean are attractive in markets
Commercial
use of GA

15. GIBBERELINS INDUCE SEED
GERMINATION

18. PLANT HORMONES
Auxins
Gibberelins
Cytokinins
Ethylene
Abscisic acid
lins

19. CYTOKININS
Cytokinin
STRUCTURE NOT
REQUIRED TO
MEMORIZE
Distribution
 Found in root and shoot tips
 Transported through xylem cells
 Found in large amounts in fruits,
germinating seeds and embryo
Functions
• Stimulate cell division and cell
enlargement
• Inhibit apical dominance
• Prevent ageing of plant parts
• Expansions of cotyledons
• Chlorophyll synthesis in chloroplast and
• Organ formation
zeatin (Corns)

22. ETHYLENE
Distribution
It is produced in fruits in higher plants, and fungi.
Most ethylene is produced by meristematic tissues
Ethylene is a gas at ordinary temperature.
Functions
 Induces fruit ripening
 Promotes senescence
 Initiate germination in peanuts
 Sprouting of potato tuber
 Promotes root growth and root-hair formation
 Induce flower formation in mango plants
Ethylene
STRUCTURE NOT
REQUIRED TO
MEMORIZE

25. ABSCISIC ACID (ABA)
Distribution
 It is a growth regulating hormone
 It is found in angiosperms,
gymnosperms, pteridophytes and
some mosses
 It is found in chloroplast of leaves
 Fruits and seeds contain highest
amount of ABA
Abscisic Acid
STRUCTURE NOT
REQUIRED TO
MEMORIZE

26. ABSCISIC ACID (ABA)
Function
• Induces dormancy of buds and seeds
• Inhibits seed-germination and development
• Stimulate closing of stomata
• It accelerates Senescence (ageing) and abscission
(falling) of leaves and other plant organs
• Create tolerance to various kinds of stress (Biotic
- insects, disease, infection etc , Abiotic -
chemicals, light, temp etc.)
• ABA acts in opposition to gibberellins

28. ABSCISSION

29. HORMONES IN ACTION