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Growth Regulators -Auxins

General Facts
•Natural forms:
•IAA (Indole-3-acetic acid ) •IBA (Indole-3-butyric acid)

•Synthetic forms:
•IBA (Indole-3-butyric acid ) •NAA (Napthalene aceticacid)

General Facts
Auxins – native and synthetic

indole-3-acetic acid (IAA)

Indole-3-butyric acid (IBA)

α-Naphthalene acetic acid (α-NAA)

2,4-dichlorophenoxyacetic acid (2,4-D) General Facts
IAA:
•Occurs in nature •Degraded by bacteria

IBA/NAA:
•Water insoluble (50% alcohol) •Stable in alcohol

•Resists •Deactivated by light degradation/deactivation (6mos) •Oxidized by•K+IBA is water soluble enzymes in planta •Combinations more effective • IBA / NAA combination synergistic

General Facts
Commercially Available Auxins
Chloromone Clonex Rooting Hormone Dip 'N GrowEZ-Clone Rooting Gel GRO-Root Hormodin #1 Hormodin #2 Hormodin #3 Jiffy-Grow Rhizopon AA #1 Rhizopon AA #2 Rhizopon AA #3 Rootone Stim-Root #1 Stim-Root #2 Woods Rooting Compound 0.05% IBA 0.3% IBA1.0 % IBA 0.3 % IBA 0.5 % IBA 0.1% IBA 0.3% IBA 0.8% IBA 0.05% IBA 0.1% IBA 0.3% IBA 0.8% IBA 0.2% NAA 0.1% IBA 0.4% IBA 1% IBA 0.5% NAA 4% Thiram fungicide 0.005% NAA 0.005% NAA Minerals and traceelements 0.5% NAA B-1 vitamin 0.25% NAA

Auxin movement- “Polar”
Shoot Apex
In shoots: Auxins move basipetally (apex to base)

General Facts

In roots: Auxins move acropetally (base to apex)Base

Root Apex

Roles of Auxin
In concert or in opposition to signals from other growth regulators
-Activation of growth at the cambial layer -Adventitious root formation -Abscission layer offlowers and fruit -Suppress budbreak (Apical dominance) -Plant cell expansion

Roles of Auxin
Auxins – promote adventitious rooting

Effect of the "rooting hormone", IBA, on hardwood cuttings ofthe tropical legume, Inga fueillei

Roles of Auxin
Auxins – inhibit lateral bud growth

Roles of Auxin
Too much auxin can suppress bud-break
• Delayed bud-break results in insufficient...
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