Gleason’s individualistic model - Competition does not cause sharp boundaries; different species do not group together due to physical variables.

TLS Online TPP Program

#Id: 7510

#Unit 6. System Physiology – Plant

IAA synthesis

IAA biosynthesis is associated with rapidly dividing and growing tissues

Primary site of auxin synthesis are shoot apical meristem and young leaves

Root apical meristem also synthesize auxin

Young fruits an seeds also have high level of auxin

TLS Online TPP Program

#Id: 7511

#Unit 6. System Physiology – Plant

TLS Online TPP Program

#Id: 7512

#Unit 6. System Physiology – Plant

TLS Online TPP Program

#Id: 7513

#Unit 6. System Physiology – Plant

Auxin biosynthesis from tryptophan (Trp). 

In the first step, Trp is converted to indole-3-pyruvate (IPyA) by the TAA family of tryptophan amino transferases. Subsequently, IAA is produced from IPyA by the YUCCA family of flavin monooxygenases.

TLS Online TPP Program

#Id: 7514

#Unit 6. System Physiology – Plant

Although free IAA is the biologically active form of the hormone but toxic in high concentration, the vast majority of auxin in plants is found in a covalently bound state are considered hormonally inactive.

IAA has been found to be conjugated to both high- and low-molecular-weight compounds.

Low-molecular-weight conjugated auxins include esters of IAA with glucose or myo-inositol and amide conjugates such as IAA-N-aspartate.

High-molecular-weight IAA conjugates include IAAglucan

TLS Online TPP Program

#Id: 7515

#Unit 6. System Physiology – Plant

The highest concentrations of free auxin in the living plant are in the apical meristems of shoots and in young leaves because these are the primary sites of auxin synthesis.