Pr, which to the human eye is blue, is converted by red light to a far-red light–absorbing form called Pfr, which is bluegreen.

TLS Online TPP Program

#Id: 10198

#Unit 6. System Physiology – Plant

The ribotide and riboside forms of trans-zeatin can be interconverted, and free transzeatin can be formed from the ribotide by the LONELY GUY (LOG) family of cytokinin nucleoside 5’ monophosphate phosphohydrolase enzymes

TLS Online TPP Program

#Id: 10199

#Unit 6. System Physiology – Plant

IPT1, IPT3, IPT5, and IPT8 are located in plastids, and the relative expression levels of IPT3 and IPT5 are higher than the other IPTs

TLS Online TPP Program

#Id: 10200

#Unit 6. System Physiology – Plant

KNOX gene expression increases cytokinin levels in the shoot apical meristem by upregulating the cytokinin biosynthetic gene ISOPENTENYL TRANSFERASE7 (IPT7)

TLS Online TPP Program

#Id: 10201

#Unit 6. System Physiology – Plant

Cytokinin Primary site of synthesis -- root tips.

High concentrations -- immature seeds and developing fruits

TLS Online TPP Program

#Id: 10202

#Unit 6. System Physiology – Plant

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: 10203

#Unit 6. System Physiology – Plant

Biological effects of cytokinins

Removes inhibitory phosphate

Promotes accumulation of G1 cyclins (CycD)