auxin

1. PHYTOHORMONES
AUXINS

2. Learning
objectives
 To know about the discovery & biosynthesis
of auxins
 To understand the physiological role of these
growth promoters in plant growth and
development
 To know the applications of these phyto
hormones auxins in Agriculture and
horticulture
 To differentiate between auxins , gibberellins
& cytokinins

3. Phyto hormones (ఫైటో హార్మో న్
లు)
Organic substances synthesized in one
part of the plant and translocated to
other parts where in very low
concentration bring about
physiological response.
మొక్క ల లో ఒక్ ప్రదేశం లో సంశ్ల ేషితమయ్యి వేరొక్ ప్రదేశం లోని చర్యి స్థ
ా నం వద్ద
అతి లప గాఢత లో ప్ియాతమ క్ అనుప్ియను ప్ెరేపంచే రస్థయన రదార్యా లను
ఫైటో హార్మో న్ లు అంటారు.

4. Phyto hormones include
 Auxins
 Gibberellins
 Cytokinins
 Abscissic acid &
 Ethylene
(Brassino steroids, Jasmonic acid, Salicylic acid are
also recognized as plant growth regulators by some
physiologists)

5. AUXINS

6. DISCOVERY OF
AUXINS

7. DISCOVERY OF AUXINS
Charles Darwin’s experiment on canary
grass coleoptiles

8. Boysen & jensen experiment on avena coleoptiles
Agar/gelatin foil inserted Mica sheet inserted

9. F.W Went’s experiment on avena coleoptiles

10. Differential distribution of auxins lead to enlargement of
cells and bending

11. • The term auxin was coined
by F.W Went
•Greek word - Auxien
• Auxien means to grow

12. Occurrence of Auxins

14. Bio synthesis of Auxins
Tryptophan is the precursor of IAA . Tryptophan is
converted to IAA in plants in different pathways
1. Indole pyruvic acid (IPyA) path way
2. Tryptamine path way.
3. Indole acetaldoxine
4. Tryptomol path way
IAA also synthesized from
Indole 3-glycerol phosphate/ Indole

15. PHYSIOLOGICAL
EFFECTS OF
AUXINS

16. AUXINS
1.Cell enlargement 6.Roots formation
2.Cell division 7.Flowering
3.Cell differentiation 8.Parthenocarpy
4.Tropical movements 9.Inhibition of Abscission
5Apical dominance 10. Weedicides

18. Cell enlargement
క్ణవ్యి కోచం

19. enlargementక్ణవ్యి కోచం
Auxins stimulate cell wall loosening
factors there by increasing elasticity
that leads to cell elongation .
ఆిి నుే వలన క్ణం లో ప్ద్వ్యభిసరణ
శక్మ మ్ ెరుగును క్ణక్వచం వదులు
చేయు ఆర్.యన్.యే మరియు
ప్ోటీనులు సంశ్ల ేషించబడి,క్ణక్వచం
వదులయ్యి క్ణవ్యి కోచం జరుగును.

20. Cell division
Promotes cell division in shoot apices, roots and cambium.
Promotes cell division in Tissue culture

21. Cell differentiation-క్ణ
విభేద్నం
Auxins promote cell differentiation
Differentiation of vascular tissues xylem and phloem from cambium during
secondary growth
Induce cell differentiation and regeneration of vascular tissues when
wounded.

22. TROPIC MOVEMENTS IN
PLANTS
Auxins induce phototropism
and gravitropism

24. Photo tropic movements- bending in
plants

25. PHOTOTROPISM AND GRAVITROPISM
The growth movements in plants in response to light is called phototropism
The growth movements in plants in response to gravity is called gravitropism
The tropic movements in plants are due to the differential distribution of
auxins

26. The stem grows positively phototrophic and
negatively geotropic
Root grows negatively phototrophic and
positively geotropic

27. అప్గాధిక్ి త
Suppression of lateral
buds by the terminal
bud is called apical
dominance
అప్ర కోరక్ము లో ఉతప త్తి
అయ్యన ఆిి న్ లు పార్ వ
కోరకాల ెరుగుద్లను ను
నిరోధించుటను అప్గాధిక్ి త
అంటారు

28. Apical dominance -
అప్గాధిక్ి త

30. Roots formation (వేరే
ఉతప త్తి)
Auxins promote root formation at
extremely low concentrations
At higher concentrations
elongation of roots is inhibited but
adventitious root formation is
enhanced.

31. Auxins like IAA,IBA,NAA enhance adventitious root formation from stem
cuttings

32. క్ృప్త్తమ ఆిి నుే IBA,NAA లను
ఉరయోగంచి కాండ ఛేదాల నుండి
వేరుే ఉతప త్తి చేసి ఫలాల , అలంక్రణ
మొక్క ల ను అభివృద్ధి చేస్తిన్నా రు

33. FLOWERING (పుష్పప తప త్తి)
Auxins also initiate flowering & development of reproductive organs
Higher auxin concentrations enhance production of female flowers in cannabis
and cucurbita

34. FRUIT FORMATION
Auxins promotes Fruit
formation in apples, cucumbers,
and tomatoes.
Auxin concentration increases
after pollination & fertilization

35. PARTHENO CARPY
(అనిషేక్ ఫలనం)
Exogenous application of auxins
induce Parthenocarpy in orchids,
cucumbers, watermelon, papaya
and tomatoes

39. Applications of synthetic auxins in agriculture &
horticulture
NAA,IBA induce root initiation in stem cuttings.
2,4 -D, 2,4,5-T,MCPA are used as herbicides to
prevent dicot weed plants
 NAA induces simultanous flowering in pine apple.
NAA, 2,4 –D are used to prevent premature leaf and
fruit fall
Parthenocarpic fruits induced in watermelon,
grapes, tomatoes, straw berries