When the magnitude of the generator potential reaches about 10 mV, an action potential is produced at the first node of Ranvier.

TLS Online TPP Program

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#Unit 6. System Physiology – Plant

Organo-genesis

TLS Online TPP Program

#Id: 10114

#Unit 6. System Physiology – Plant

Indole-3-acetic acid (IAA) occurs in all plants, 

Peas contain 4-chloroindole-3-acetic acid. 

Mustards and corn contain indole-3- butyric acid (IBA).

TLS Online TPP Program

#Id: 10115

#Unit 6. System Physiology – Plant

Rapidly dividing tissues, shoot apical meristems, young leaves, and developing fruits and seeds are the primary sites of IAA synthesis.

TLS Online TPP Program

#Id: 10116

#Unit 6. System Physiology – Plant

IAA is synthesises by tryptophan and is primarily synthesized in a two-step process 

Indole-3-pyruvate (IPyA) as the intermediate. 

The second step in the pathway is carried out by the YUCCA gene product, a tryptophan aminotransferase.

TLS Online TPP Program

#Id: 10117

#Unit 6. System Physiology – Plant

Auxins in biological samples can be determined by bioassay, mass spectrometry, or enzyme-linked immunosorbent assay (ELISA).

The Avena coleoptile curvature assay is a sensitive measure of auxin activity (it is effective for IAA concentrations of about 0.02 to 0.2 mg L–1).

TLS Online TPP Program

#Id: 10118

#Unit 6. System Physiology – Plant

Trp transaminase

Tryptophan (Trp)-----------------------→ Indole-3-pyruvic acid

IPA decarboxylase

(IPA) -----------------------→ Indole-3-acetaldehyde (IAld)

---------------------------------------→ Indole-3-acetic acid (IAA)