Environmental and Experimental Botany 44 2000 221 – 229
Classical and biochemical endpoints in the evaluation of phytotoxic effects caused by the herbicide trichloroacetate
Claudemir Marcos Radetski , Sylvie Cotelle, Jean-Franc¸ois Fe´rard
Centre des Sciences de l
’
En6ironnement, Uni6ersite´ de Metz,
1
, rue des Re´collets,
57000
Metz, France Received 31 March 2000; received in revised form 7 July 2000; accepted 8 July 2000
Abstract
Three terrestrial plant species, oat A6ena sati6a , Chinese cabbage Brassica campestris cv. chinensis and lettuce Lactuca sati6a, were exposed to different concentrations of herbicide TCA sodium trichloroacetate in a growth test
according to guideline OECD c 208. Classical i.e. germination and biomass and biochemical i.e., antioxydant enzyme activities endpoints were investigated. Germination rate decreased significantly at 3.9 mg TCA kg dry soil
− 1
for oat and lettuce and 62.5 mg TCA kg dry soil
− 1
for Chinese cabbage. Biomass decreased significantly only at 1.9 mg TCA kg dry soil
− 1
for oat and lettuce and 15.6 mg TCA kg dry soil
− 1
for Chinese cabbage. The activities of superoxide dismutase EC 1.15.1.1, catalase EC 1.11.1.6, peroxidase EC 1.11.1.7 and glutathione reductase EC
1.6.4.2 increased significantly at the lowest concentration of TCA tested, i.e. 0.03 mg TCA kg dry soil
− 1
for oat and lettuce and 0.48 mg TCA kg dry soil
− 1
for Chinese cabbage. Our results showed a ranking of sensitivity among the different endpoints for the three plant species: enzyme activities \ biomass \ germination rate. The increase in
antioxidant enzyme activities observed in this study ensured the detoxification of increased levels of active oxygen species, and presumably prevented the plants from undergoing oxidative stress damage. Thus, the use of enzyme
activities will permit the detection of early injury in plant growth testing. © 2000 Elsevier Science B.V. All rights reserved.
Keywords
:
A6ena sati6a; Biomarkers; Brassica campestris; Lactuca sati6a; Oxidative stress; Phytotoxicity www.elsevier.comlocateenvexpbot
1. Introduction
The two chlorinated aliphatic compounds 2,2- dichloropropionic
acid dalapon
and trichloroacetic acid TCA were widely used as
herbicides Foy, 1969; Ashton and Crafts, 1981. Both compounds are particularly effective against
grasses, but they also control certain broad leaf weeds.
The most
important application
of trichloroacetic acid sodium salt herbicide is the
use for the management of aquatic plants in drainage and in supply canals Bowmer, 1987.
TCA is still used for various purposes in industry e.g. plastic, galvanization and textile, and maybe
the least harmful of the C
2
halogenated acids that
Correspoding author. Present adress: Departamento de Quı´mica, Universidade Federal de Santa Catarina, 88040-900
Floriano´polis SC, Brazil. E-mail address
:
radetskiqmc.ufsc.br C.M. Radetski. S0098-847200 - see front matter © 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 0 9 8 - 8 4 7 2 0 0 0 0 0 6 9 - 1
are formed in the atmosphere by photochemical processes Mu¨ller et al., 1996; Hashimoto et al.,
1998. It is readily absorbed by roots and leaves and primarily translocated via the transpiration
stream system. However small amounts are trans- ported via the symplast system Blanchard, 1954.
The initial step of plant injury caused by TCA is regarded as a modification of protein structure
and such changes could alter enzyme activity and membrane permeability Ashton and Crafts,
1981.
On the other hand, when plants are subjected to stress of many kinds physical, chemical, bio-
logical, bursts of active oxygen occur within min- utes after exposure Foyer et al., 1994. Although
the formation of toxic oxygen species is generally considered to be detrimental to cellular function,
these molecules are formed in normal cell metabolism and their production and destruction
is a regulated phenomenon Asada, 1993. An imbalance between oxidants and antioxidants in
favor of the oxidants, potentially leading to dam- age, is termed oxidative stress Sies, 1997. Up to
date, there is no report of active oxygen species associated with TCA toxicity.
Plants are well adapted for minimizing damage that could occur from toxic oxygen species. The
natural antioxidative defence system Elstner, 1982; Winston, 1990; Smirnoff, 1993; Sies, 1997
includes three general classes: a lipid soluble, membrane-associated antioxidants e.g. alpha-to-
copherol and beta-carotene; b water soluble reductants e.g. tripeptide glutathione and ascor-
bate; and c enzymatic antioxidants including superoxide dismutase, catalase, peroxidase and
the enzymes involved in the synthesis and regener- ation of the reduced forms of the antioxidants
e.g. enzymatic pool of glutathione. This system is present in both intra- and extra-cellular com-
partments. Since oxidative stress comprises a complex set of phenomena, it is highly unlikely
that a single response will provide a general marker for it, thus simultaneous increase in sev-
eral components of the antioxidative defence sys- tem would be necessary in order to obtain a
substantial increase in stress tolerance Foyer et al., 1994. Plant antioxidant enzyme activities
were considered as relevant endpoints in different stress situations, they have been investigated
mainly with air pollutants and metals Keller, 1974; Van Assche et al., 1988 and reviews were
published giving some theoretical rationale for using biomarkers Ernst and Peterson, 1994;
Vangronsveld et al., 1997.
In the present investigation, three terrestrial plants, oat A6ena sati6a, Chinese cabbage
Brassica campestris cv. chinensis and lettuce Lactuca sati6a, were exposed to different con-
centrations of herbicide TCA in a growth test according to guideline of Organization for Eco-
nomic Cooperation and Development 1984. The phytotoxic effects of soil contaminated with TCA
were measured by classical endpoints i.e. germi- nation rate and biomass and by biochemical
endpoints antioxidant enzyme activities. The purposes of this work were i to investigate more
sensitive endpoints for evaluating TCA contami- nated soils; ii to examine the ratios of sensitivity
between classical and biochemical endpoints car- ried out simultaneously according to the same
phytotoxicity protocol. As a matter of fact, the utilization of guidelines offers the advantage of
minimizing differences in the generation of results, and thus comparison of phytotoxicity results can
be more realistic and feasible.
It is proposed that changes in enzyme activities might be used as plant biomarkers in the evalua-
tion of the phytotoxicity of soils contaminated by the chlorinated aliphatic herbicides.
2. Materials and methods
