Interaction Effects of Nitrogen Rates and Forms Combined With and Without Zinc Supply on Plant Growth and Nutrient Uptake in Maize Seedlings

Previous studies have shown that zinc (Zn) accumulation in shoot and grain increased as applied nitrogen (N) rate increased only when Zn supply was not limiting, suggesting a synergistic effect of N on plant Zn accumulation. However, little information is available about the effects of different mineral N sources combined with the presence or absence of Zn on the growth of both shoot and root and nutrient uptake. Maize plants were grown under sand-cultured conditions at three N forms as follows: NO3– nutrition alone, mixture of NO3–/NH4+ with molar ratio of 1:1 (recorded as mixed-N), and NH4+ nutrition alone including zero N supply as the control. These treatments were applied together without or with Zn supply. Results showed that N forms, Zn supply, and their interactions exerted a significant effect on the growth of maize seedlings. Under Zn-sufficient conditions, the dry weight (DW) of shoot, root, and whole plant tended to increase in the order of NH4+ < NO3– < mixed-N nutrition. Compared with NH4+ nutrition alone, mixed-N supply resulted in a 27.4 and 28.1% increase in leaf photosynthetic rate and stomatal conductance, which further resulted in 35.7 and 33.5% of increase in shoot carbon (C) accumulation and shoot DW, respectively. Furthermore, mixed-N supply resulted in a 19.7% of higher shoot C/N ratio vs. NH4+ nutrition alone, which means a higher shoot biomass accumulation, because of a significant positive correlation between shoot C/N ratio and shoot DW (R2 = 0.682***). Additionally, mixed-N supply promoted the greatest root DW, total root length, and total root surface area and synchronously improved the root absorption capacity of N, iron, copper, manganese, magnesium, and calcium. However, the above nutrient uptake and the growth of maize seedlings supplied with NH4+ were superior to either NO3– or mixed-N nutrition under Zn-deficient conditions. These results suggested that combined applications of mixed-N nutrition and Zn fertilizer can maximize plant growth. This information may be useful for enabling integrated N management of Zn-deficient and Zn-sufficient soils and increasing plant and grain production in the future.

The protective role of vitamins (E + C) on Nile tilapia (Oreochromis niloticus) exposed to ZnO NPs and Zn ions: Bioaccumulation and proximate chemical composition

The accumulation potency of zinc nanoparticles in Nile tilapia (Oreochromis niloticus) were previously studied but their impacts on proximate chemical composition in muscle tissue by describing the dose-dependent accumulation and the protective role of vitamins (E + C), have not been investigated. Therefore, this study was carried out to assess the protective role of vitamins (E + C) on Zn accumulation in muscle and gill tissues of O. niloticus exposed to three sublethal concentrations (1/8 LC50, 1/4 LC50, and 1/2 LC50) of zinc oxide nanoparticles (ZnO NPs) compared to zinc oxide bulk particles (ZnO BPs) as well as their effects on the induced chemical composition alterations for different experimental periods (7, 14, 21, and 28 day). The data displayed that fish exposed to the different sublethal concentrations of ZnO NPs or ZnO BPs have a significant increase (p<0.05) in Zn ions accumulation in muscle and gill tissues compared to control group but Zn was accumulated in gill tissue higher than muscle tissue at all exposure periods. Also, Zn accumulation was higher in fish tissues exposed to ZnO NPs than ZnO BPs. On the other hand, groups supplemented with vitamins (E + C) showed a significant decreasing (p<0.05) in accumulated Zn levels compared to groups without supplementation. The values of these supplemented groups returned to similar levels established in the control at low concentrations but still higher than control at the high concentrations. Furthermore, the results showed that moisture and ash content slightly increased while protein and fat decreased in fish exposed to ZnO NPs or ZnO BPs compared to control group. In conclusion, the findings supported that a combination of vitamins (E + C) reduced Zn accumulation and ameliorated chemical composition alterations in O.niloticus fish.

Accumulation of heavy metal pollution caused by traffic in forest trees in the park of Kerey and Janibek Khans of the city of Nur-Sultan, Kazakhstan

Air quality in Nur-Sultan, the fast-growing new capital city of Kazakhstan, has been poorly investigated. This research was carried in Kerey and Janibek Khans Park in Nur-Sultan, the capital city of Kazakhstan, which is affected by “different traffic density” on the roads. Three different categories of contamination (i) high pollution (distance from the main road 10–15 m), (ii) moderate pollution (distance from the side road 15–30 m), and (iii) low pollution (distance from the source of contamination 30–80 m) at different levels resulting from urban transportation were examined. The aim of the study is to determine the pollution accumulation amounts of Ni, Cd, Pb, Cr, Li, Co, Fe, and Zn in five different tree species: Norway spruce (Picea abies /L./ H. Karst.), blue spruce (Picea pungens Engelm.), Scots pine (Pinus sylvestris L.,), Siberian larch (Larix sibirica Ledeb.), and silver birch (Betula pendula Roth). Significant differences in Ni, Cd, Pb, Cr, Li, Co, Fe, and Zn accumulation amounts were determined between three different parts of the park exposed to different levels of contamination. Approximately twice higher Ni, 2.3 times Cd, 3.3 times Pb, 2.7 times Co, 1.6 times Zn accumulation were determined in the area exposed to high pollution than in the parts of the park exposed to low pollution. Cd deposition in the area exposed to high contamination was higher in silver birch than in Scots pine and Norway spruce, while Cr and Co deposition values were higher in Norway spruce than in birch and Scots pine.

Arabidopsis thaliana zinc accumulation in leaf trichomes is correlated with zinc concentration in leaves

Zinc (Zn) is a key micronutrient for plants and animals, and understanding Zn homeostasis in plants can improve both agriculture and human health. While root Zn transporters in plant model species have been characterized in detail, comparatively little is known about shoot processes controlling Zn concentrations and spatial distribution. Previous work showed that Zn hyperaccumulator species such as Arabidopsis halleri accumulate Zn and other metals in leaf trichomes. To date there is no systematic study regarding Zn accumulation in the trichomes of the non-accumulating, genetic model species A. thaliana. Here, we used Synchrotron X-Ray Fluorescence mapping to show that Zn accumulates at the base of trichomes of A. thaliana. Using transgenic and natural accessions of A thaliana that vary in bulk leaf Zn concentration, we demonstrate that higher leaf Zn increases total Zn found at the base of trichome cells. Our data indicates that Zn accumulation in trichomes is a function of the Zn status of the plant, and provides the basis for future studies on a genetically tractable plant species to understand the molecular steps involved in Zn spatial distribution in leaves.

Interaction between Polyphenolic Antioxidants and Saccharomyces cerevisiae Cells Defective in Heavy Metal Transport across the Plasma Membrane

Natural polyphenols are compounds with important biological implications which include antioxidant and metal-chelating characteristics relevant for their antimicrobial, antitumor, or antiaging potential. The mechanisms linking polyphenols and heavy metals in their concerted actions on cells are not completely elucidated. In this study, we used the model eukaryotic microorganism Saccharomyces cerevisiae to detect the action of widely prevalent natural polyphenols on yeast cells defective in the main components involved in essential heavy metal transport across the plasma membrane. We found that caffeic and gallic acids interfered with Zn accumulation, causing delays in cell growth that were alleviated by Zn supplementation. The flavones morin and quercetin interfered with both Mn and Zn accumulation, which resulted in growth improvement, but supplemental Mn and especially Zn turned the initially benefic action of morin and quercetin into potential toxicity. Our results imply that caution is needed when administering food supplements or nutraceuticals which contain both natural polyphenols and essential elements, especially zinc.

Arabidopsis thaliana zinc accumulation in leaf trichomes is correlated with zinc concentration in leaves

Zinc (Zn) is a key micronutrient. In humans, Zn deficiency is a common nutritional disorder, and most people acquire dietary Zn from eating plants. In plants, Zn deficiency can decrease plant growth and yield. Understanding Zn homeostasis in plants can improve agriculture and human health. While root Zn transporters in plat model species have been characterized in detail, comparatively little is known about shoot processes controlling Zn concentrations and spatial distribution. Previous work showed that Zn hyperaccumulator species such as Arabidopsis halleri accumulate Zn and other metals in leaf trichomes. The model species Arabidopsis thaliana is a non-accumulating plant, and to date there is no systematic study regarding Zn accumulation in A. thaliana trichomes. Here, we used Synchrotron X-Ray Fluorescence mapping to show that Zn accumulates at the base of trichomes of A. thaliana, as had seen previously for hyperaccumulators. Using transgenic and natural accessions of A. thaliana that vary in bulk leaf Zn concentration, we demonstrated that higher leaf Zn increases total Zn found at the base of trichome cells. Furthermore, our data suggests that Zn accumulates in the trichome apoplast, likely associated with the cell wall. Our data indicates that Zn accumulation in trichomes is a function of the Zn status of the plant, and provides the basis for future studies on a genetically tractable plant species aiming at understanding the molecular steps involved in Zn spatial distribution in leaves.