Mitochondria use different origin sequences to initiate replication of each DNA strand

Replication of the H strand is initiated in a D loop.

Replication of the L strand is initiated when its origin is exposed by the movement of the first replication fork.

TLS Online TPP Program

#Id: 7553

#Unit 6. System Physiology – Plant

TLS Online TPP Program

#Id: 7554

#Unit 6. System Physiology – Plant

Ratio of GA:ABA affects early germination (vivipary).   With high levels of ABA, seeds remain dormant.  

TLS Online TPP Program

#Id: 7555

#Unit 6. System Physiology – Plant

TLS Online TPP Program

#Id: 7556

#Unit 6. System Physiology – Plant

Cytokinins are defined as compounds that have biological activities similar to those of trans-zeatin. These activities include the ability to do the following:

Induce cell division in callus cells in the presence of an auxin

Promote bud or root formation from callus cultures when in the appropriate molar ratios to auxin

Delay senescence of leaves

Promote expansion of dicot cotyledons

TLS Online TPP Program

#Id: 7557

#Unit 6. System Physiology – Plant

Dihydrozeatin (DZ) and isopentenyl adenine (iP) also are commonly found in higher plants and bacteria.

TLS Online TPP Program

#Id: 7558

#Unit 6. System Physiology – Plant

Cytokinin biosynthesis, catalyzed by isopentenyl transferase (IPT), is the addition of the isopentenyl side chain from DMAPP (dimethylallyl diphosphate) to an adenosine moiety (ATP or ADP). iPRTP or iPRDP is converted to ZTP or ZDP respectively by cytochrome P450 monooxygenase (CYP735A) and eventually is converted to zeatin.