Bionanotechnology Applications in Plants and Agriculture - Bionanotechnology: Global Prospects - page 525

26.3.3 Nanoparticle Zinc Oxide
A.study.by.Lin.and.Xing 22 .examined.the.internalization.and.upward.translocation.of.ZnO.
nanoparticles.by. Lolium perenne .(ryegrass).and.compared.the.results.to.Zn +2 .salts..Uptake.and.
phytotoxicity.of.nanoparticles.were.visualized.by.light.and.electron.microscopy..In.the.pres-
ence.of.ZnO.nanoparticles,.ryegrass.biomass.was.signiicantly.reduced,.root.tips.shrank,.and.
root.epidermal.and.cortical.cells.collapsed..The.effects.of.Zn +2 .salts.at.similar.concentrations.
were.less..Therefore,.the.phytotoxicity.of.ZnO.nanoparticles.was.due.to.the.nanoparticles.and.
not.their.dissolution.in.the.bulk.nutrient.solution..The.authors.observed.that.ZnO.nanoparti-
cles.adhered.to.the.root.surface,.and.individual.ZnO.nanoparticles.were.observed.in.apoplast.
and.protoplast.tissues.of.the.root.endodermis.and.stele..Finally,.their.conclusions.also.showed.
that.little.(if.any).ZnO.nanoparticles.would.translocate.up.the.ryegrass.stems.
26.3.4 Nanoparticle Copper
Another.study.explored.bioaccumulation.of.non-water-soluble.nanoparticle.copper.on.the.
growth. of. plant. seedlings. 23 . The. plant. species. examined. were. Phaseolus radiatus . (mung.
bean).and. Triticum aestivum .(wheat)..Growth.inhibition.of.seedlings.exposed.to.different.
concentrations.of.Cu.nanoparticles.was.examined.in.plant.agar.media,.and.data.suggested.
that.all.concentrations.tested.were.toxic.to.both.plants..Experiments.showed.that.cupric.
ion. released. from.Cu.nanoparticles. had.negligible.effects.in.the.concentration.ranges.of.
the.present.study,.and.that.the.apparent.toxicity.clearly.resulted.from.nanoparticles..The.
authors.proposed.that.the.plant.agar.test.is.a.good.protocol.for.testing.the.phytotoxicity.of.
non-water-soluble.nanoparticles.
26.3.5 Nanoparticle Silver
A.study.of.the.uptake.and.sequestration.of.silver.nanoparticles.was.reported. 24 .The.authors.
examined. the. uptake. of. silver. nanoparticles. using. two. common. metallophytes,. Indian.
mustard.( Brassica juncea ).and.alfalfa.( Medicago sativa )..Indian.mustard.accumulated.up.to.
12.wt%.silver.when.exposed.to.an.aqueous.substrate.containing.1,000.ppm.AgNO 3 .for.72.
h,.while.alfalfa.accumulated.up.to.14.wt%.silver.when.exposed.to.an.aqueous.substrate.
containing. 10,000. ppm. AgNO 3 . for. 24. h.. In. both. cases. the. silver. was. stored. as. discrete.
nanoparticles,.with.a.mean.size.of.50.nm.
26.3.6 Carbon Nanotubes
Possible.toxic.effects.of.multiwalled.carbon.nanotubes.(MWNTs).on.rice.cells.( Oryza sativa
L.).were.investigated. 25 .When.a.rice.cell.suspension.was.cultured.with.MWNTs,.an.increase.
in.reactive.oxygen.species.(ROS).and.a.decrease.in.cell.viability.were.observed..When.the.
antioxidant.ascorbic.acid.was.introduced.into.the.medium,.the.ROS.content.decreased.and.
cell. viability. increased.. Transmission. electron. microscopy. revealed. individual. tubes. in.
contact.with.cell.walls..The.rice.suspension.cells.with.individual.MWNTs.associated.with.
their.cell.walls.seemed.to.undergo.a.hypersensitive.response.known.as.the.ROS.defense.
response.cascade,.which.led.to.decreased.viability.
26.3.7 Mechanistic Studies of Nanoparticle Toxicity
The.phytotoxicity.of.alumina.nanoparticles.loaded.with.and.without.the.chemical.phenan-
threne.was.investigated.by.means.of.root.elongation.experiments. 26 .Five.plant.species,. Zea
mays .(corn),. Cucumis sativus .(cucumber),. Glycine max .(soybean),. Brassica oleracea .(cabbage),.