Many plant tissues contain the enzyme cytokinin oxidase, which cleaves the side chain from zeatin (both cis and trans), zeatin riboside, iP, and their N-glucosides, but not their O-glucoside derivatives

TLS Online TPP Program

#Id: 10169

#Unit 6. System Physiology – Plant

KNOXI gene and GA2 oxidase are primary regulators of GA

TLS Online TPP Program

#Id: 10170

#Unit 6. System Physiology – Plant

Auxin promotes the transcription of GA3ox and to repress the transcription of GA2ox

TLS Online TPP Program

#Id: 10171

#Unit 6. System Physiology – Plant

Gibberellins Enhance Cell Wall Extensibility without Acidification.

Enzyme Expansins and Xyloglucan endotransglycosylase (XET) is involved in gibberellin-promoted wall extension. The function of XET may be to facilitate the penetration of expansins into the cell wall.

TLS Online TPP Program

#Id: 10172

#Unit 6. System Physiology – Plant

Three main classes of mutations affecting plant height have

been selected:

1. Gibberellin-insensitive dwarfs

2. Gibberellin-deficient mutants in which the gibberellin deficiency has been overcome by a second “suppressor” mutation, so the plants look closer to normal

3. Mutants with a constitutive gibberellin response (“slender” mutants)

TLS Online TPP Program

#Id: 10173

#Unit 6. System Physiology – Plant

GAI and RGA proteins normally act as repressors of gibberellin responses. Gibberellin acts indirectly through an unidentified signaling intermediate, which is thought to bind to the regulatory domains of the GAI and RGA Proteins. 

TLS Online TPP Program

#Id: 10174

#Unit 6. System Physiology – Plant

DELLA is feedback regulator