Larger populations are more resistant to extinctions.

Greater ranges of habitats promote increased speciation rates.

TLS Online TPP Program

#Id: 7540

#Unit 6. System Physiology – Plant

TLS Online TPP Program

#Id: 7541

#Unit 6. System Physiology – Plant

Compounds such as AMO-1618, Cycocel, and Phosphon D are specific inhibitors of the first stage of gibberellin biosynthesis, and they are used as growth height reducers.

TLS Online TPP Program

#Id: 7542

#Unit 6. System Physiology – Plant

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

TLS Online TPP Program

#Id: 7543

#Unit 6. System Physiology – Plant

Gibberellins Enhance Cell Wall Extensibility without Acidification. Gibberellin has no effect on the osmotic parameters but has consistently been observed to cause an increase in both the mechanical extensibility of cell walls and the stress relaxation of the walls of living cells. the 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: 7544

#Unit 6. System Physiology – Plant

Three main classes of mutations affecting plant height have been selected:

Gibberellin-insensitive dwarfs

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

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

TLS Online TPP Program

#Id: 7545

#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.