Chemicals Mitigate Copper Toxicity on Seed
Germination and Plant Growth
Marouane Ben Massoud1, 2*, Oussama Kharbech1 and Abdelilah Chaoui1
1University of Carthage, Faculty of Sciences of Bizerte, LR18ES38 Plant Toxicology and
Environmental Microbiology, 7021 Zarzouna, Tunisia
2School of Biological, Earth and Environmental Sciences, University College Cork, Distillery
Fields, North Mall Cork, Ireland
Ben Massoud, University of Carthage,
Faculty of Sciences of Bizerte, LR18ES38
Plant Toxicology and Environmental
Microbiology, 7021 Zarzouna, Tunisia
School of Biological, Earth and
Environmental Sciences, University College
Cork, Distillery Fields, North Mall Cork,
The present mini review aimed to explain the potential protective role of some chemicals against Copper
(Cu) toxicity in plant. Many studies suggest that the exogenous supply of effectors such as nitric oxide,
polyamines, organic acids and growth regulators to germinating seeds can be a promising alternative to
improve plant response to heavy metal stress.
Heavy metal stress is one of the environmental pollution situations affecting plant growth
and productivity. Copper is an essential oligo-element, but can be toxic to most plants, even
at very low concentration [1,2]. Due to its wide use in fungicides, pesticides and fertilizers,
pollution by Cu has become increasingly a major environmental problem: inhibition of plant
growth , resulting from numerous physiological and metabolic disturbances, is generally
reported as a consequence of an excess of Cu . Copper is readily absorbed by plants, leading
to toxic symptoms of physiological and biochemical dysfunctions, such as disorders in mineral
nutrition  and photosynthesis , deterioration of membrane integrity and, in general,
induction of oxidative stress due to overproduction of reactive oxygen species (ROS) [1,2].
ROS are considered to be both (i) harmful to cells  and (ii) ubiquitous signaling
molecules participating in the stress response of plants . Like other environmental stresses,
Cu excess results in changes in
a) antioxidant enzyme activities, such as superoxide dismutase, catalase and
b) contents of low-molecular-weight non-enzymatic antioxidants, such as ascorbic
acid and glutathione.
Most of the abiotic stress impact studies in plants have been carried out for individually
applied pollutants, although contamination, which really involves soils and plants, is multiple
rather than simple. Soils are often contaminated with several pollutants at the same time.
In such situations, contaminants can interact with one another in a synergistic, additive or
protective manner .
Several researchers suggested that it would be important to develop practical techniques
to mitigate the effects of heavy metal stress, such as the simultaneous application of nitric
oxide , polyamines , sulfur , calcium , citrate , hydrogen peroxide ,
growth regulators , and hydrogen sulfide [15,16], which neutralize the toxic effect of
heavy metals on germination and plant growth and thereby improve plant resistance.
Many chemicals have the capacity to trap and sequester metal
cations inside cells. The strong affinity to the binding of heavy metals
is due to the electronegativity of functions in these molecules; in
particular carboxyl groups (-COO-). This is the case with EDTA 
and organic acids (malic, oxalic, citric, benzoic) [1,18,19].
However, the action of the chelators remains controversial.
These compounds can improve the solubility of metal cations in the
rhizosphere and, as a result, their uptake by roots. In this case, they
are useful in ongoing phytoextraction programs that are relevant to
the phytoremediation stream [17,20].
Chelators also participate in intracellular detoxification:
vacuolar shuttles in the form of “metal-organic acid” complexes
eliminate the heavy metals from the cytoplasm [18,21]. A third
possibility would be an indirect action of certain carboxylic acids
(citrate) in improving the antioxidant capacities of plants previously
contaminated with heavy metals [18,22,23].
Clarification of why Cu phytotoxicity could be mitigated
by exogenous effectors application should provide a basis for
early monitoring and assessment of contamination of the plant
environment. At least in part, the protection of plants against the
toxicity of heavy metals is associated with the control of their
Professor, Chief Doctor, Director of Department of Pediatric Surgery, Associate Director of Department of Surgery, Doctoral Supervisor Tongji hospital, Tongji medical college, Huazhong University of Science and Technology