IT IS USEFULL FOR THE PHARMCY STUDENTS FOR BACHELOR OF PHARMCY AND DOCTOR OF PHARMCY STUDENTS FOR B.PHARM SECOND YEAR STUDENTS AND SECOND YEAR DOCTOR OF PHARMACY STUDENTS

1. E.SURESH BABU M.PHARM
DEPARTMENT OF PHARMACOGNOSY
VIKAS INSTITUTE OF PHARMACEUTICAL SCIENCES
NEAR AIR PORT, RAJAHMUNDRY-533103

2. Plant Hormones (Phytohormones)
• Plant hormones (Phytohormones) are
physiological intercellular messengers that control
the complete plant lifecycle, including
• Germination
• Rooting
• Growth
• Flowering
• fruit ripening
• Foliage and death.

3. Plant Hormones (Phytohormones)
• Plant hormones are regulators of almost all
aspects of plant development and plant
responses to their environment.
• Active at very low concentrations, with tight
spatial regulation of synthesis and response,
many plant hormones have key roles in the
interactions between plants and beneficial
microbes.

4. Significance of Plant Hormones (Phytohormones)
• Plant hormones are secreted in response to
environmental factors such as
• Excess of nutrients
• Drought conditions
• Light
• Temperature
• Chemical or Physical stress.
• So, levels of hormones will change over the
lifespan of a plant and are dependent upon
season and environment.

5. Classification
• The plant growth regulators are classified into
Synthetic and Natural.
• The synthetic regulators are also known as
Exogenous regulators
• The Natural are called the endogenous

6. Five major classes of plant hormones
• Auxins
• Cytokinins
• Gibbereilins
• Abscisic acid
• Ethylene
• Plant growth regulators have made the way for
plant tissue culture techniques, which were a
real boon for mankind in obtaining
therapeutically valuable secondary metabolites.

7. Auxins
• The term Auxins is derived from the Greek word
auxein which means to grow.
• Auxins were the first plant hormones discovered.
Charles Darwin was among the first scientists to
pool in plant hormone research.
• Salkowski (1885) discovered indole-3-acetic acid
(IAA) in fermentation media.
• IAA is the major auxin involved in many of the
physiological processes in plants.
• Auxins are used to induce cell elongation in
stems.

8. Functions of auxin
• Stimulates cell elongation.
• The auxin supply from the apical bud
suppresses growth of lateral buds.
• Removal of the apical bud results in growth of
the axillary buds.
• Auxin has various effects on leaf and fruit
abscission, fruit set, development, and
ripening, and flowering.

9. Cytokinins
• Cytokinins are compounds with a structure
resembling adenine which promote cell
division.
• They also regulate the pattern and frequency
of organ production as well as position and
shape.

10. • Cytokinin have been found in almost all higher
plants as well as mosses, fungi, bacteria, and
also in many prokaryotes and eukaryotes.
There are more than 200 natural and synthetic
cytokinins identified.
• Cytokinin concentrations are more in
meristematic regions and areas of continuous
growth potential such as roots, young leaves,
developing fruits, and seeds.

11. Functions of cytokinin
• Stimulate cell division (cytokinesis).
• Stimulate morphogenesis (shoot initiation/bud
formation) in tissue culture.
• Stimulate the growth of lateral (or adventitious) buds
release of apical dominance.
• Stimulate leaf expansion resulting from cell
enlargement.
• Promotes the conversion of etioplasts into chloroplasts
via stimulation of chlorophyll synthesis.
• Stimulate the dark-germination of light-dependent
seeds. Delays senescence. Promotes some stages of
root development.

12. • Kinetin was the first Cytokinins identified and
so named because of the compounds ability
to promote cytokinesis (cell division).
• Though it is a natural compound, it is not
made in plants, and is therefore usually
considered a ‘synthetic’ cytokinin.
• The common naturally occurring cytokinin in
plants today is called zeatin which was
isolated from corn.

13. • May enhance stomatal opening in some
species.
Effect of cytokinin on stomatal opening

14. Ethylene
• Ethylene has been used in practice since the
ancient times,
• Where people would use gas figs in order to
stimulate ripening, burn incense in closed
rooms to enhance the of pears.
• It was in 1864, that leaks of gas from street
lights showed stunting of growth, twisting of
plants, and abnormal thickening of stems.

15. Functions of ethylene
• Production stimulated during ripening, flooding,
stress, senescence, mechanical damage,
infection.
• Regulator of cell death programs in plants
(apoptosis).
• Stimulates the release of dormancy.
• Stimulates shoot and root growth and
differentiation (triple response).
• Regulates ripening of climacteric fruits.

16. • Induction of femaleness indioecious flowers.
• Stimulates flower opening.
• Stimulates leaf and fruit abscission.
• Flowering in most plants is inhibited by
ethylene. Mangos, pineapples and some
ornamentals are stimulated by ethylene.
• Stimulates flower and leaf senescence.

17. Gibberellins
• They are a group of diterpenoid
acids that functions as plant
growth regulators influencing a
range of developmental
processes in higher plants
including stem elongation,
germination, dormancy,
flowering, sex expression,
enzyme induction and leaf and
fruit senescence.

18. • The gibberellins are named GA1 Gan in order
of discovery. Gibberellic acid was the first
gibberellin to be structurally characterized as
GA3.There are currently 136 GAs identified
from plants, fungi and bacteria

19. Functions of gibberellins
• Stimulates stem elongation by stimulating cell
division and elongation. GA controls internode
elongation in the mature regions of plants.
• Dwarf plants do not make enough active
forms of GA.
• Flowering in biennial plants is controlled by
GA. Biennials grow one year as a rosette and
after the winter, they bolt (rapid expansion of
internodes and formation of flowers).

20. Functions of gibberellins
• Breaks seed dormancy in some plants that require
stratification or light to induce germination.
• Stimulates α-amylase production in germinating cereal
grains for mobilization of seed reserves.
• Stimulates germination of pollen and growth of pollen
tubes.
• Induces maleness in dioecious flowers(sexexpression).
• Can cause parthenocarpic (seedless) fruit development
or increase the size of seedless fruit (grapes).
• Can delay senescence in leaves and citrus fruits.

21. Abscisic Acid
• The abscisic acid stimulates the closure of
stomata (water stress brings about an increase
in ABA synthesis)
Closure of stomata and water stress brings about an increase in ABA synthesis

22. Functions of abscisic acid
• Involved in abscission of buds, leaves, petals,
flowers, and fruits in many, if not all,
instances, as well as in dehiscence of fruits.
• Production is accentuated by stresses such as
water loss and freezing temperatures.
• Involved in bud dormancy.
• Prolongs seed dormancy and delays
germination
• Inhibits elongation.

23. • ABA is implicated in the control of elongation,
lateral root development, and geotropism, as
well as in water uptake and ion transport by
roots.
• ABA coming from the plastids promotes the
metabolism of ripening.
• Promotes senescence.
• Can reverse the effects of growth stimulating
hormones

24. Brassinosteroids
• Brassinosteroids may be a new class of plant
growth substances.
• They are widely distributed within the plant
kingdom, they have an effect at extremely low
concentrations, both in bioassays and whole
plants, and they have a range of effects that
are different from the other classes of plant
substances

25. Functions of Brassinosteroids
• Promote shoot elongation at low concentrations.
• Strongly inhibit root growth and development.
• Promote ethylene biosynthesis and epinasty.
• Interfere with ecdysteroids (moulting hormones)
in insects

26. • Enhance xylem differentiation.
• Decrease fruit abortion and drop.
• Enhance resistance to chilling, disease,
herbicide, and salt stress.
• Promotion of germination.
• Promote changes in plasmalemma
energization and transport, assimilate uptake.

27. Salicylic Acid
• Salicylic acid has been known to be present in
some plant tissues.
• Salicylic acid is synthesized from the amino acid
phenylalanine.
• SA is thought by some to be a new class of plant
growth regulator.
• It is a chemically characterized compound,
ubiquitously found in the plant kingdom and has
an effect on many physiological processes in
plants at low concentrations.

28. Functions of salicylic acid
• Promotes flowering.
• Stimulates thermogenesis in Arum flowers.
• Stimulates plant pathogenesis protein
production (systemic acquired resistance).
• May enhance longevity of flowers.
• May inhibit ethylene biosynthesis.
• May inhibit seed germination.

29. Than Q