1. Next generation plant growth
regulators in horticulture
production
Credit Seminar

2. Plant Growthregulator?
• An organic compound,
• Can be natural or synthetic,
• It modifies or controls one or more specific
physiological processes within a plant but the site
action is different.

3. Classification of PGRP’s
NO Growth regulator Example
1 AUXINS IAA, IBA, NAA, 2,4-D
2 Gibberellins Gibberellic acid
3 Cytokinins Kinetin, Zeatin
4 Ethylene Ethylen
5 Dormins Abscissic Acid
6 Flowering hormones Florigen, Anthesin, Vernalin
7 Miscellaneous natural substances Cyclitols, Vitamins, Phytochrome, Traumatic
substances etc
8 Phenolic substances Coumarin
9 Synthetic growth retardants CCC, Phosphon D, Morphactons, Maleic
hydrazode (MH) etc.
10 Miscellaneous synthetic substances Synthetic Auxins, synthetic cytokinins etc.

4. Major classes of PGR’S
1. Auxins
2. Gibbrellins Plant Growth Promoters
3. Cytokinins
4. Ethylene
5. Abscisic acid
Plant Growth Inhibitors

5. Auxins
• The Word Auxins originally derived from the
Greek word (auxein)- ‘’To grow/Increase”.
• First Isolated from human urine.
• Produced by the growing apex of stem and
roots of the plants

6. Types f Auxins
Natural
Synthetic IBA, 2,4-D, NAA
Indole -3- Acetic acid
(IAA)

7. Signal-transduction pathways in
plants

8. Gibberellins
• Second most important growth Hormone.
• Gibberellins are named after the fungus
Gibberella fujikuroi which causes rice plants to
grow abnormally tall.
• synthesized in apical portions of stems and
roots.
• More than 60 types of Gibberellins are known.

9. Cytokinins
• First time isolated from coconut milk.
• Synthesized in root apex, endosperm of seeds,
young fruits, where cell division takes place.

10. Abscic Acid
• Also known as dormins, which acts as anti-
Gibberellins.
• It is Synthesized in leaves of wide variety of
plants .
• Responsible of closing stomata during drought
condition, hence acts as plant stress hormone.

11. The new generation of phytohormons
The list of phytohormones expanded to include new chemicals :
1. Brassionosteroids (BR),
2. Jasmonic acid (JA),
3. Salicylic acid (SA),
4. Polyamines,strigolactones (SL),
5. Nitric oxide (NO) and
6. Peptide hormones (Santner et al., 2009)

12. Brassinosteroids (BRs)
• Brassinosteroids (BRs), are class of plant
polyhydroxysteroids that recognized as new
kind of phytohormones.
• The occurrence of brassinosteroids (BRs) has
been demonstrated in almost every part of
plants.
• about 70 BRs have been isolated from plants.
(Bajguz and Tretyn, 2003)

13. THE CELLULAR MECHANISMS OF BR
REGULATINGPLANT DEVELOPMENT
At cellular levels, BRs can regulate
• cell elongation
• cell division
• cell differentiation
• At whole-plant levels, BRs can regulate
• Hypocotyl elongation
• Root and shoot development
• Leaf developmentt
• Male fertility
• Senescence
• Responses to biotic and abiotic stresses

14. A Graph shows the Roles of BR s in Regulating Plant
Development

15. jasmonic acid (JA)
• Jasmonic acid (JA) is derived from the fatty
acid linolenic acid It is a member of the
jasmonate class of plant hormones.
• The major function of JA and its various
metabolites is regulating plant responses to
abiotic and biotic stresses as well as plant
growth and development

16. jasmonic acid (JA)
• Regulated plant growth and development
processes include growth inhibition, senescence,
flower development and leaf abscission.
• JA is responsible for tuber formation in potatoes,
yams, and onions.
• It has an important role in response to
wounding of plants and systematic acquired
resistance.

17. jasmonic acid (JA)
• Levels of jasmonic acid rise in response to
damage .
• The action of jasmonic acid induces the
transcription of many genes involved in plant
defense.

18. Salicylic acid
• Salicylic acid is a monohydroxy benzoic acid,
a type of phenolic acid and a betahydroxy acid.
• Colorless crystalline organic acid
• widely used in organic synthesis and functions
as a plant hormone.
• Derived from the metabolism of salicin.

19. •Phenolic compounds exert their influence on
physiological and biochemical processes
including, photosynthesis, ion uptake, membrane
permeability, enzyme activities, flowering and
growth and development of plants.
ROLE OF SALICYLIC ACID

20. Case study

21. Bean (Phaseolus vulgaris L.) and tomato
(Lycopersicon esculentum L.).
Fourteen day-old plants were soil-drenched
with 20 ml of distilled water or 0.05, 0.1, 0.5, 1.0
and 5.0 mM ASA or SA.
 Alternatively, seeds were imbibed in the
solutions for 24 h and sown in pots.

22. • One week after soil-drenching or three weeks
after the seed treatment, seedlings were
subjected to heat, cold and drought stresses.
For heat treatment, seedlings were exposed to
54 0.5 C for 3 h with an average light intensity
of 40 Mol m−2sec−1 and then returned to room
temperature. For chilling stress, plants were
exposed to 0 0.5 C in an incubator with an
average light intensity of 35 Mol m−2sec−1
• and 16/8 h light/dark photoperiod for two days.

23. • Drought stress was imposed by withholding
water for 7 days, then on the 8th day all pots
were watered until saturation.

24. Survival (%) of SA or ASA – treated tomato and
bean plants after heat, cold and drought stress

25. • Bean plants A) exposed to heat stress
• B) pre-treated as a soil drench with 0.5 mMASA
and exposed to heat stress
• Bean plants A) exposed to heat stress
• B) pre-treated as a soil drench with 0.5 mMASA and exposed to
heat stress

26. C) Exposed to chilling D) pre-treated as a soil drench
with 0.5 mM ASA and subjected to chilling

27. E) subjected to drought F) pre-treated as a soil
drench with 0.5 mM ASA and subjected to drought.

28. • The physiological and biochemical basis molecular biology of
SA induced SAR is not clear at present.
• The similarity of the injury mechanism between pathogenesis
and stress leads us to hypothesize that SA which induces
resistance to disease also confers tolerance to environmental
stress.
• Salicylic acid (SA) and acetyl salicylic acid (ASA) provide
multiple stress tolerance in plants and that salicylic acid and its
derivatives regulate the expression of stress tolerance.
Conclusion

29. Thank you…