Zinc oxide nanoparticles (ZnO NPs) have a wide range of applications in cosmetics, electrical, and optical industries. The wide range of applications of ZnO NPs, especially in personal care products, suggest they can reach major environmental matrices causing unforeseen effects. Recent literature has shown conflicting findings regarding the beneficial or detrimental effects of ZnO NPs towards terrestrial biota. In this review we carried out a comprehensive survey about beneficial, as well as detrimental aspects, of the ZnO NPs exposure toward various terrestrial plants. A careful scrutiny of the literature indicates that at low concentrations (about 50 mg/kg), ZnO NPs have beneficial effects on plants. Conversely, at concentrations above 500 mg/kg they may have detrimental effects, unless there is a deficiency of Zn in the growing medium. This review also remarks the critical role of the biotic and abiotic factors that may elevate or ameliorate the impact of ZnO NPs in terrestrial plants.

This experiment examined the effects of sulfate (S) and reduced glutathione (GSH) on arsenic uptake by arsenic hyperaccumulator Pteris vittata after exposing to arsenate (0, 15 or 30 mg As L-1) with sulfate (6.4, 12.8 or 25.6 mg S L=1) or GSH (0, 0.4 or 0.8 mM) for 2-wk. Total arsenic, S and GSH concentrations in plant biomass and arsenic speciation in the growth media and plant biomass were determined. While both S (18–85%) and GSH (77-89%) significantly increased arsenic uptake in P. vittata, GSH also increased arsenic translocation by 61-85% at 0.4 mM (p < 0.05). Sulfate and GSH did not impact plant biomass or arsenic speciation in the media and biomass. The S-induced arsenic accumulation by P. vittata was partially attributed to increased plant GSH (21-31%), an important non-enzymatic antioxidant countering oxidative stress. This experiment demonstrated that S and GSH can effectively enhance arsenic uptake and translocation by P. vittata.

Zinc or copper deficiency and salinity are known soil problems and often occur simultaneously in agriculture soils. Plants undergo various changes in physiological and biochemical processes to respond to high salt in the growing medium. There is lack of information on the relation of exogenous application of Zn and Cu with important salinity tolerance mechanisms in plants. Therefore, the present study was conducted to determine the effect of foliar Zn and Cu on two maize cultivars (salt-tolerant cv. Yousafwala Hybrid and salt-sensitive cv. Hybrid 1898). Salinity caused a significant reduction in water and turgor potentials, stomatal conductance, and transpiration and photosynthetic rate, while increase in glycine betaine, proline, total soluble sugars, and total free amino acids was evident in plants under saline regimes. Furthermore, there was significant decline in P, N, Ca, K, Mn, Fe, Zn, and Cu and increase in Na and Cl contents in plants fed with NaCl salinity. Nitrate reductase activity was lower in salt-stressed plants. However, foliar application of Zn and Cu circumvented salinity effect on water relations, photosynthesis, and nutrition and this was attributed to the better antioxidant system and enhanced accumulation of glycine betaine, proline, total free amino acids, and sugars. The results of the present study suggested that Zn application was superior to Cu for mediating plant defense responses under salinity.

Bacterial associations with plant roots are thought to contribute to the success of phytoremediation. We tested the effect of addition of a polycyclic aromatic hydrocarbon contaminated soil on the structure of the rhizosphere microbial communities of wheat (Triticum aestivum), lettuce (Lactuca sativa var. Tango), zucchini (Cucurbita pepo spp. pepo var. Black Beauty), and pumpkin (C. pepo spp. pepo var. Howden) 16S rDNA terminal restriction fragment length polymorphism (T-RFLP) profiles of rhizosphere microbial communities from different soil/plant combinations were compared with a pairwise Pearson correlation coefficient. Rhizosphere microbial communities of zucchini and pumpkin grown in the media amended with highest degree of contaminated soil clustered separately, whereas communities of these plants grown in unamended or amended with lower concentrations of contaminated soil, grouped in a second cluster. Lettuce communities grouped similarly to cucurbits communities, whereas wheat communities did not display an obvious clustering. The variability of 16S rDNA T-RFLP profiles among the different plant/soil treatments were mostly due to the difference in relative abundance rather than presence/absence of T-RFLP fragments. Our results suggest that in highly contaminated soils, the rhizosphere microbial community structure is governed more by the degree of contamination rather than the plant host type.

Sodium chloride is the most often used chemical to malt ice and snow on the roads and has negative effects on the roadside environment. Searching for ways to improve the conditions for growth of trees and shrubs near the roads becomes an urgent matter. One such method of improving growth conditions for plants under salinity might be to use organic matter (green waste compost) and mycorrhizal fungi. This study studied the effect of application in soil different salts on several trees and shrubs growth in growing media. Also, effect of green waste compost and arbuscular mycorrhiza (AM) added to the growing medium was evaluated in terms of growth and K+, Ca+2, and Na+ uptake. The highest pH of the growing medium was noted when sodium carbonate was used. The pH ranged from 8.7 to 9.0 after eight doses of sodium carbonate. The pH of the growing medium was also significantly higher regardless of whether or not green waste compost or mycorrhizal fungi were used. The type of growing medium had a great effect on the growth of most of the trees, but among shrubs the growing medium was only important for Cornus alba, Sambucus nigra, and Spiraea vanhouttei. Growth of all these plants was much better under salinity when green waste compost or green waste compost with AM fungi was used. In all the cases, when salinity of the growing medium retarded growth of trees and shrubs, sodium chloride was the compound that had the strongest growth retarding effect. Leaf ionic composition was significantly affected by salinity in the growing medium, and in some cases also by micorhizal fungi. The type of growing medium had various effects on sodium uptake, depending on species. In most cases, the addition of green waste compost to the growing medium caused a greater amount of sodium in the leaves of tested plants. The use of mycorrhizal fungi had no effect on the uptake of sodium, compared to the control plants (without AM fungi).

Phenylalanine ammonia-lyase activity (PAL, EC 4.3.1.5), total phenolics, soluble proteins, malondialdehyde and metals accumulation in four-week old chamomile (Matricaria chamomilla) plants cultivated in nutrient solution and exposed to low (3 μM) and high (60 and 120 μM) levels of cadmium (Cd) or copper (Cu) for 7 days were studied. High Cd concentrations had a stimulatory effect on PAL activity and soluble phenolics accumulation while high Cu doses decreased soluble proteins in the leaf rosettes. In the roots, extreme stimulatory effects of 60 and 120 μM Cu were observed on PAL activity, phenolics and malondialdehyde accumulation, while protein content was reduced by these Cu doses. Cd accumulation was higher in the leaf rosettes compared to copper, but the opposite was recorded in the roots. Taken together, the stimulatory effect of Cu on phenolic metabolism was recorded, even though high malondialdehyde accumulation may be an indication that phenolics was not sufficient to counteract reactive oxygen species formation thus leading to damage of membrane integrity. In comparison to Cd, Cu had more noticeable effect on the parameters studied to support its strong redox-active properties. These facts in correlation to antioxidative properties of phenolic metabolites are also discussed.

The generation of ozone microbubbles (O₃MB) is an effective means of sterilizing plant culture media against bacteria and pathogens; however, the use of O₃MB can induce precipitation of metal ions from the medium, such as iron (Fe) and manganese (Mn), that are important to plant growth. Here, we evaluated whether addition of a chelator, either ethylenediaminetetraacetic acid (EDTA) or diethylenetriaminepentaacetic acid (DTPA), could prevent this side effect of O₃MB sterilization. We compared nutrient composition, medium sterility, and plant growth after various treatments (0, 0.1, 0.01, 0.001, or 0.0001% (w/v) of EDTA and DTPA addition after O3MB generation). Metal chelators (EDTA and DTPA) are widely used in algal and plant growth solutions to maintain iron (Fe) solubility in hydroponic solutions, EDTA is used in agriculture to remove heavy metals from heavily contaminated soils and also as a plant fertilizer, and DTPA has a wide range of applications including removal of heavy metals from agricultural soils. Thus, the available evidence indicates that addition of a chelator after O₃MB generation may prevent precipitation of oxidized Fe or Mn in a culture medium. The addition of a chelator resulted in a concentration-dependent reduction in precipitates and the maintenance of Fe and Mn concentrations in the medium. Although O₃MB sterilization did not affect plant growth, the addition of a chelator at concentrations of 0.1, 0.01, or 0.001% (w/v) had a significant deleterious effect. However, at a concentration of 0.0001%, the chelator had no significant effect on plant growth but did result in the maintenance of a higher Fe and Mn concentration compared to the O₃MB treated control. The addition of a chelator did not alter the sterilizing effects of O₃MB. These results indicate that the addition of a chelator at a concentration of 0.0001% to an O₃MB-sterilized culture medium enabled the retention of dissolved Fe and Mn without affecting plant growth. The use of O₃MB, plus a chelator, is an effective disinfection method in hydroponic culture.

Thirty strains of fungi collected from nature were investigated for their ability to grow on agar medium contaminated with Remazol Brilliant Blue R (RBBR) and 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT). The results showed that strain U97, later identified as Trametes versicolor, was the most active decomposer. This fungus decolorized 85 % of RBBR in 6 h and degraded 71 % of DDT in 30 days. In RBBR decolorization, high-performance liquid chromatography analysis revealed that two peaks were identified as metabolic products. Among inducers for ligninolytic enzymes, only veratryl alcohol improved RBBR decolorization and DDT degradation by 93 % and 77 %, respectively. A partial least squares method using Minitab 15 showed that lignin peroxidase exhibited a positive correlation to the abilities of T. versicolor U97 to decolorize RBBR and degrade DDT. A multivariate linear equation, with the same values of ligninolytic activity during RBBR decolorization and DDT degradation, revealed that 1 % RBBR decolorization represented 1.16 % DDT degradation. Screening with agar or liquid medium and improvement of the mathematical modeling could have practical importance in the exploitation of T. versicolor U97 for the removal of DDT on a commercial scale.