Factors Determining the Toxicity of Organic Pollutants to Animals and Plants - Organic Pollutants: An Ecotoxicological Perspective - page 58

taBLe 2.7
mechanism of action of Pollutants in Plants and fungi
Pollutants type of toxic action Site of action consequence comments reference

Triazine and substituted
urea herbicides

Photosynthesis inhibitors Q B binding site of the D1

protein in photosystem 11

Inhibition of electron
transport in chloroplast and
consequent reduction of
photosynthesis

These herbicides have
generally very low toxicity
to animals

Hassall (1990),
Sjut (1997)

Phenoxyakanoic
herbicides

Disruption of growth
regulation of plants

Unknown, but apparently
the same as for the natural
auxins whose action they
mimic

Distorted growth patterns
including malformed leaves
and epinasty of stems

2,4-D, MCPA, CMPP, and
MCPB are examples,
generally of low toxicity to
animals

Hassall (1990)

Dinitroaniline herbicides Mitotic disrupters Polymerase responsible for

microtubule formation

Disruption of cell division Examples include triluralin

and oryzalin

Hassall (1990)

Paraquat Photosynthesis inhibitor Electron transport system

of photosystem 1

Paraquat diverts electrons
from the electron transport
system to oxygen to form
O 2 , which causes cellular
damage

Paraquat and related
herbicides are toxic to
animals because they form
reactive oxyradicals (see
Chapter 14)

Hassall (1990),
Sjut (1997)

DNOC Mitochondrial poison Inner membrane of

mitochondrion

Uncouples oxidative
phosphorylation by running
down the proton gradient
across inner mitochondrial
membrane

DNOC and certain other
dinitrophenols are general
biocides because the
mitochondrion is present in
most living organisms

Hassall (1990),
Nicholls (1982)

Ergosterol biosynthesis
inhibitors (EBIs)

Inhibitors of ergosterol
biosynthesis in fungi

Fungal cytochrome P450
involved in sterol
metabolism

Destabilizing of fungal
membranes

Some EBIs are inducers and
or inhibitors of P450 forms
of animals (see Section 2.6)

Kato (1986)