DISCOVERY OF CYTOKININS SEARCH FOR CELL DIVISION FACTORS THAT WOULD ALLOW PLANT TISSUES TO DIVIDE IN TISSUE CULTURE CELL DIVISION ACTIVITY IDENTIFIED IN COCONUT MILK CELL DIVISION ACTIVITY ALSO FOUND IN VASCULAR TISSUES ADENINE FOUND TO BE SLIGHTLY ACTIVE OLD BOTTLE OF DNA FOUND TO HAVE STRONG ACTIVITY, BUT NOT NEW BOTTLE KINETIN IDENTIFIED AS DEGRADATION PRODUCT OF DNA

KINETIN (6-furfurylaminopurine) (Discovered as a cell division factor)

STRUCTURE OF BENZYLADENINE (BA) - ANOTHER SYNTHETIC CYTOKININ

trans-Zeatin (The Naturally Occurring Cytokinin)

Biological isoprene unit

( active form)

CYTOKININ DEGRADATION

Tobacco plants overexpressing gene for cytokinin oxidase EFFECT OF CYTOKININ DEFICIENCY ON GROWTH OF TOBACCO PLANTS WILD TYPE

Wild-type Tobacco

Tobacco overexpressing cytokinin oxidase

Wild-type CO Overexpressor

Wild- type root tip

CO Overexpressor root tip  Cytokinin inhibits root growth

INCREASING IAA CONCENTRATION INCREASING CK CONCENTRATION

OVEREXPRESSION OF Cyclin D3 (CYCD3) BYPASSES THE CYTOKININ REQUIREMENT FOR CELL DIVISION

Crown gall tumor on tomato stem (Agrobacterium tumefaciens)

TWO MAJOR OPINES FOUND IN CROWN GALL TUMORS GENES FOR OPINE SYNTHESIS PRESENT ON T-DNA FROM AGROBACTE RIUM

Witches’ broom on balsam fir (Corynebacterium fascians)

Protonemal filaments of the moss, Funaria. (Control)

Protonemal filaments of the moss, Funaria. (Treated with Benzyladenine)

BUD FORMATION IN THE MOSS, Funaria

EFFECT OF CYTOKININ ON LEAF SENESCENCE CYTOKININ- TREATED

CYTOKININ CAUSES CELLS TO BECOME SINKS

CYTOKININ INHIBITS SENESCENCE

CYTOKININ PROMOTES EXPANSION OF RADISH COTYLEDONS

CYTOKININ SIGNALING INVOLVES A TWO- COMPONENT SYSTEM