Size effect of iron (III) oxide nanomaterials on the growth, and their uptake and translocation in common wheat (Triticum aestivum L.).

Nanomaterials (NMs) have emerged in the last decades and are used in many disciplines such as industry, material sciences, biomedicine, biotechnology, bioenergy, and agriculture. The size of the NMs is a critical factor that affects NMs' integration and transfer into the biological systems. Therefore, this study aims at investigating the effect of NMs-size on i) plant growth and physiology, and ii) NMs uptake and translocation in plant tissues. For these purposes, iron (III) oxide (Fe2O3) NMs with varied sizes, 8-10, 20-40, and 30-50 nm, have been applied to wheat plants in a hydroponic system. Results showed that Fe2O3 NMs enhanced root length, plant height, biomass, and chlorophyll content of wheat. Confocal microscopy analysis indicated that Fe2O3 NMs cause injury in root-tip cells without a visible toxic symptom. Vibrating sample magnetometer (VSM), and inductively coupled plasma-mass spectroscopy (ICP-MS) analyses of leaf tissues revealed that all tested NMs were up taken by wheat plant and translocated to the leaves. Iron content was found to be dramatically increased in NMs-treated plant tissues, which possibly contributed to the growth enhancement. Experiments confirmed that Fe2O3 NMs with 20-40 nm size is much more efficient in plant growth compared to those with 8-10 and 30-50 nm size. Overall, Fe2O3 NMs with 20-40 nm in size could be proposed as a nano-fertilizer for agricultural applications. On the other hand, the translocation of NMs in the wheat plant requires further investigation of their effects on the end users.

Uptake, translocation, and physiological effects of hematite (α-Fe2O3) nanoparticles in barley (Hordeum vulgare L.).

There has been a growing concern with the environmental influences of nanomaterials due to recent developments in nanotechnology. This study investigates the impact and fate of hematite nanoparticles (α-Fe2O3 NPs) (∼14 nm in size) on a crop species, barley (Hordeum vulgare L.). For this purpose, hematite NPs (50, 100, 200, and 400 mg/L) were hydroponically applied to barley at germination and seedling stages (three weeks). Inductively coupled plasma mass spectrophotometry (ICP-MS) along with vibrating sample magnetometer (VSM) techniques were used to track the NPs in plant tissues. The effects of NPs on the root cells were observed by scanning electron microscopy (SEM) and confocal microscopy. Results revealed that α-Fe2O3 NPs significantly reduced the germination rate (from 80% in control to 30% in 400 mg/L), as well as chlorophyll (36-39%) and carotenoid (37%) contents. Moreover, the treatment led to a significant decline in the quantum yield of photosystem II (Fv/Fm). Leaf VSM analysis indicated a change in magnetic signal for NPs-treated samples compared with untreated ones, which is mostly attributed to the iron (Fe) ions incorporated within the leaf tissue. Besides, Fe content in the roots and leaf had gradually increased by the increasing doses of NPs, which was confirming NPs' translocation to the aerial parts. Microscopic observations revealed that α-Fe2O3 NPs altered root cell morphology and led to the injury of cell membranes. This study, in the light of our findings, shows that α-Fe2O3 NPs (∼14 nm in size) are taken up by the roots of the barley plants, and migrate to the plant leaves. Besides, NPs are phytotoxic for barley as they inhibit germination and pigment biosynthesis. This inhibition is probably due to the injury of the cell membranes in the roots. Therefore, the use of hematite NPs in agriculture and thereby their environmental diffusion must be addressed carefully.