Lecture Plant physiology continue

PLANT PHYSIOLOGY
Faculty of Biology
Hanoi University of Sciences – VNU

2014


Natural Auxins

IAA

4-Cl-IAA


Synthetic Auxins

IBA

dicamba

NAA

2,4-D

picloram

2,4,5-T


Auxin synthesis pathways

free

conjugated Forms


Auxin affects both cell division and
enlongation
A

B

C


Phototropism


Gravitropism


Thigmotropism
is growth in response to touch
Rapid leaf movements in response to
mechanical stimulation are examples of
transmission of electrical impulses called
action potentials


Apical dominance

Auxin and Cytokinin affect apical
dominance together


Stimulation of root development

Auxin

Without auxin


Inhibitions of abscises


Auxin distribution

Embryo development

Lateral root initiation

Main root


Auxin transportation


Control auxin transportation

- Auxin efflux carrier has
main role in directing auxin
transportation.
- PINs and ABCBs
distribution affects auxin
transportation.


Auxin signaling mechanism


Cytokinins - named after cytokinesis
- Miller,Skook et al. (1955)
found a compound that
strongly promotes cell
division called kinetin.
- Letham và Miler (1963)
isolated cristal natural
cytokinin from maize corn
and called zeatin. Activity of
zeatin is higher than kinetin
10 – 100 times.
- Cytokinin are also
synthesised and benzyladenin
is very commonly used in
tissue culture.


Cytokinin biosynthesis

Cytokinin: free – conjugated forms

Free form

Riboside conjugation

Nucleotide conjugation


Physiological activities of CK


Cytokinin increase the growth


With auxin control cell differentiation

Cytokinin > Auxin

SHOOT

Cytokinin < Auxin

ROOT


Cytokinins as anti-aging hormones
Cytokinins can retard aging of some
plant organs, perhaps by inhibiting

protein breakdown, stimulating RNA
and protein synthesis, and mobilizing
nutrients. May slow leaf deterioration
on plants since detached leaves dipped
in acytokinin solution stay green
longer.


Nutrient Mobilizing