Agriculture Reference
In-Depth Information
complex (Collom et al.
2008
). Therefore, this strategy can be considered as an
interesting approach to introduce NO into plants, using CNTs and visible light.
9.3.7.7 Graphenes
Bacterial spot caused by
Xanthomonas perforans
is a major disease of tomatoes,
leading to reduction in production by 10-50 %. Due to the appearance of resistance
to copper-based bactericides, it developed DNA-directed silver (Ag) nanoparticles
(NPs) grown on graphene oxide (GO) (Ag@dsDNA@GO). Low concentrations of
Ag@dsDNA@GO led to efficient antibacterial capability in culture with significant
advantages in improved stability, enhanced antibacterial activity, and stronger
adsorption properties without any phytotoxicity (Ocsoy et al.
2013
).
The effects of graphene on shoot growth, root, biomass, shape, cell death, and
ROS of cabbage, tomato, red spinach, and lettuce were analyzed by Begum
et al. (
2011
). The concentrations used in the study ranged from 500 to
2,000 mg L
1
, which is extremely high for biological systems. Combined morpho-
logical and physiological analyses indicated that after 20 days of exposure under
experimental conditions, graphene significantly inhibited plant growth and biomass
level, in a dose-dependent manner. Due to this, high graphenes oxide was also
detected in ROS and cell death as well as visible symptoms of necrotic lesions. This
effect was observed on cabbage, tomato, and red spinach mediated by oxidative
stress necrosis. No effects were observed with lettuce seedlings under the same
conditions (Fugetsu and Begum
2011
; Jastrzebska et al.
2012
).
Graphene at 0-80 mg L
1
effect on suspensions of
A. thaliana
(Columbia
ecotype) T87 cells showed morphological changes and the adverse effects such as
fragmented nuclei, membrane damage, and mitochondrial dysfunction. Analysis of
intracellular ROS demonstrated that graphene induced a 3.3-fold increase in ROS,
suggesting that ROS are key mediators in the cell death signaling pathway. Trans-
mission electron microscopy study showed graphene entering into the cells by
endocytosis. Then the authors suggested that graphene induced cell death in T87
cells through mitochondrial damage mediated by ROS (Begum and Fugetsu
2013
).
Again, this study is showing a toxic effect at high graphene concentration.
To assess biomass accumulation (physiological response), few-layer graphene
materials were introduced into adequate media (50 mg L
1
) together with tomato
seeds, and the germination and growth were followed (Khodakovskaya et al.
2011
).
It is interesting that the few-layer graphene carbon structures did not significantly
affect plant growth rates, probably because of their inability to penetrate plant
tissues.
Graphene oxide on wastewater microbial community was toxic in dose depen-
dent, especially in concentrations over 50 mg L
1
. The authors suggested that
possibly the ROS generation could be one of the responsible mechanisms for the
toxic effect of GO (Ahmed and Rodrigues
2013
).
