Nanomaterials and nanotechnology have been widely applied in the last decade. As nanoparticles become more and more popular, the risk of exposure from nanoparticles also increases. There is now an extensive debate about the risks and benefits of the many manufactured nanomaterials into the environment. Nanoparticles are introduced into the soil, water and environment as a result of human activities. Because of their widespread use in consumer products it is expected that nanomaterials will find their way into aquatic, terrestrial and atmosphere environments. Nanoparticles might leach into the water from landfill runoff or become airborne as part of garbage . Their fate and behavior are largely unknown.
Nanomaterials and plants
To examine the toxicity of nanotechnology on plant functions a team of researchers from China treated cells from rice plant species Arabidopsis with carbon nanotubes to assess the viability of cells, damage to DNA, and the presence of reactive oxygen species and find the effect of nanotubes on plant cells. They found an increase in levels of the reactive oxygen species, hydrogen peroxide causes oxidative stress to cells which can cause cell death with higher dose. But cells exposed to carbon particles that were not nanotubes did not suffer any ill effects. According to the researchers "The current study has provided evidence that certain carbon nanoparticles are not 100% safe and have side effects on plants, suggesting that potential risks of nanotoxicity on plants need to be assessed,"
Another research revealed that ZnO nanoparticles at certain concentrations could adsorb onto ryegrass root surface, damage root tissues, enter root cells, and inhibit seedling growth. Inhibition of root growth varied greatly among nanoparticles and plants and partially correlated to nanoparticles concentration.
Investigation on the dissolution of ZnO nanoparticles and its contribution to the phytotoxicity revealed that in the presence of ZnO nanoparticles, ryegrass biomass significantly reduced, root tips shrank, and root epidermal and cortical cells highly vacuolated or collapsed.
Magnetic nanoparticles in small concentrations had a stimulating effect on the growth of the plantlets while the enhanced concentration of aqueous ferro fluid solution induced an inhibitory effect.

Similarly nano alumin particles did not have a negative effect on the growth of Phaseolus vulgaris and Lolium perenne in the tested concentration range. Metal nanoparticles influence the growth of Lactuca seeds and increase the shoot/root length.
Researchers at University of Delaware, in Newark, found that pumpkin plants can take up magnetite - magnetic iron oxide - nanoparticles through their roots and that the particles are transported around the plant.
A study shows that nanoparticles are transported inside the plants and are present both in the extra cellular space and within some cells and likewise smaller Pd nanoparticles cause stress effects in leaves of a selected plant at low concentration in nutrient solution.
Certain plants take up a significant amount of magnetite nanoparticles from liquid growth medium and to accumulate them within roots and leaves particularly silver nanoparticles.
Tomato seeds exposed to CNTs germinated faster and grew into larger, heavier seedlings than other seeds.
Auburn University researchers state that tomato plants uptake the silver nanoparticles from the hydroponic solution and these silver nanoparticles led to the death of the plants. It was also found that the smaller the silver nanoparticles, the quicker the tomato plants die.
Cerium dioxide nanoparticles exposed either as aerosol or as suspension indicated that the biological barriers of plants are more resistant against nanoparticle translocation.
Scientists have also reported the first evidence that CNTs penetrate the hard outer coating of seeds, and have beneficial effects. Nanotube-exposed seeds sprouted up to two times faster than control seeds and the seedlings weighed more than twice as much as the untreated plants. Those effects may occur because nanotubes penetrate the seed coat and boost water uptake.
The phytotoxicity of nano-CeO2, nano-La2O3, nano-Gd2O3 and nano-Yb2O3 on radish, rape, tomato, lettuce, wheat, cabbage and cucumber were investigated by the Chinese researchers. They found that root growth varied greatly between different nanoparticles and plant species.
A study indicated that silver nanoparticles inhibited seed germination at lower concentrations, but showed no clear size-dependant effects, and never completely impeded germination.
Researchers at the New Jersey Institute of Technology in Newark tested and found that varying concentrations of aluminum oxide nanoparticles on hydroponically grown species cabbage, carrot, corn, cucumber and soybean resulted in a significant reduction in root growth.
It is not strange to find both positive and negative effects of nanoparticles on higher plants. It is clear that different plants have different response to the same nanoparticles. However, limited or no information is available on plant cell internalization of nanoparticles or other particles. Researches report positive or negative evidence for the toxicity of nanoparticles as it depends on their property, test organism species, and surrounding solution conditions.
Despite the scientists' observations that carbon nanotubes had toxic effects on plant cells, the use of nanotechnology in the agriculture industry still has great promise.