Page 148 - phytochemistry general program

Synthesized by plant and broadly distributed within the plant kingdom .1
.2
Show specific biological activity at very low concentrations. .3
.4
Display multiple functions in plants
.1
Regulating physiological phenomena in a dose-dependent manner, which may
change due to changes in the sensitivity of the plant tissue during development

or due to environment.

Unlike mammalian hormones, different PGRs may interact, either synergistically
or antagonsitically, to produce a particular effect.

a) Auxines

b) Cytokinines

c) Gibberelllin

d) Abscisic acid

e) Ethylene

a) Auxines

They are produced primarily in apical and root meristems, young leaves, and
seeds in developing fruits.

Functions of auxins:
• Stimulates cell elongation
• Suppress growth of lateral buds
• IAA stimulates differentiation of vascular tissue (xylem and phloem)
• Stimulates root initiation of stem cuttings and lateral root development

in tissue culture (adventitious rooting).

The auxines most frequently employed are indole-3-acetic acid IAA (natural
auxine) and 2,4- dichlorophenoxy acetic acid (2, 4-D) which are synthetic auxines.

IAA being natural auxine, it may be subjected to enzymatic oxidation (due to IAA
oxidase present in the cultured cells), or it is rapidly degraded by light. Therefore it

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