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: 10234

#Unit 6. System Physiology – Plant

BRI1–BAK1-BR-→ BSK--→BSU1--→degradation of Phosphorylated BIN2-----→activation of BES1 & BZR1--→BR Response

TLS Online TPP Program

#Id: 10235

#Unit 6. System Physiology – Plant

Brassinosteroids, like gibberellins, suppress photomorphogenesis in the dark.

TLS Online TPP Program

#Id: 10236

#Unit 6. System Physiology – Plant

DE-ETIOLATED2 (DET2) gene, which encodes a brassinosteroid biosynthetic gene. Det2 loss-of-function mutants have reduced levels of brassinosteroids, resulting in a de-etiolated appearance of the seedling even when grown in the dark

TLS Online TPP Program

#Id: 10237

#Unit 6. System Physiology – Plant

Brassinosteroids are also required for promotion of cell

elongation by gibberellins, and gibberellin-induced degradation

of the DELLA repressor enhances the brassinosteroid response.

TLS Online TPP Program

#Id: 10238

#Unit 6. System Physiology – Plant

OsGSR1, a member of the gibberellic acid–stimulated gene family, acts as a positive regulator of both the gibberellic acid response and brassinosteroid biosynthesis.

TLS Online TPP Program

#Id: 10239

#Unit 6. System Physiology – Plant

ABA was originally thought to induce abscission, however, abscission is regulated by ethylene rather than ABA.