Mineral Composition Analysis of Red Horse-Chestnut (Aesculus × Carnea) Seeds and Hydroalcoholic Crude Extract Using ICP OES

This study presents findings on the metal and metalloid composition of red horse-chestnut (Aesculus × carnea, AXC) seeds, determined by the ICP OES technique. Samples were collected from five AXC plants located in Modena (Italy) over four consecutive years (2016-2019). The seeds underwent proximate analysis, which included measurements of moisture content, proteins, lipids, carbohydrates, ash, and elemental composition. The analysis revealed consistent values for these parameters throughout the study period. The metal content of the AXC seeds can be categorized into two groups: (i) major components, with concentrations ranging from 1 to <1500 mg/100 g dry basis (d.b.), where K was identified as the most abundant element, and (ii) minor constituents, with concentrations between 1 and <1000 μg/100 g d.b., with Li, Mo, and Ti at the lower concentration limit. Comparative analyses were performed using literature data on AHP and AHH seeds, which, like AXC, belong to the Sapindaceae family and were collected from the same area and period. A hydroalcoholic extract of AXC seeds was prepared annually and characterized, with results compared to a commercial product (AXC_herb). AXC extracts had approximately 30% higher analyte concentrations than AXC_herb, while AXC seeds showed 20-30% higher metal and metalloid levels than AHP and AHH.

Nickel toxicity in plants: reasons, toxic effects, tolerance mechanisms, and remediation possibilities-a review

Nickel (Ni) is a naturally occurring metal, but anthropogenic activities such as industrialization, use of fertilizers, chemicals, and sewage sludge have increased its concentration in the environment up to undesirable levels. Ni is considered to be essential for plant growth at low concentration; however, Ni pollution is increasing in the environment, and therefore, it is important to understand its functional roles and toxic effects on plants. This review emphasizes the environmental sources of Ni, its essentiality, effects, tolerance mechanisms, possible remediation approaches, and research direction that may help in interdisciplinary studies to assess the significance of Ni toxicity. Briefly, Ni affects plant growth both positively and negatively, depending on the concentration present in the growth medium. On the positive side, Ni is essential for normal growth, enzymatic activities (e.g., urease), nitrogen metabolism, iron uptake, and specific metabolic reactions. On the negative side, Ni reduces seed germination, root and shoot growth, biomass accumulation, and final production. Moreover, Ni toxicity also causes chlorosis and necrosis and inhibits various physiological processes (photosynthesis, transpiration) and cause oxidative damage in plants. The threat associated with Ni is increased as Ni concentration increases day by day in the environment, particularly in soils; therefore, it would be hazardous for crop production in the near future. Additionally, the lack of information regarding the mechanisms of Ni tolerance in plants further intensifies this situation. Therefore, future research should be focused on approachable and prominent solutions in order to minimize the entry of Ni into our ecosystems.

Too much is bad--an appraisal of phytotoxicity of elevated plant-beneficial heavy metal ions

Heavy metal ions such as cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), nickel (Ni), and zinc (Zn) are considered essential/beneficial for optimal plant growth, development, and productivity. However, these ions readily impact functions of many enzymes and proteins, halt metabolism, and exhibit phytotoxicity at supra-optimum supply. Nevertheless, the concentrations of these heavy metal ions are increasing in agricultural soils worldwide via both natural and anthropogenic sources that need immediate attention. Considering recent breakthroughs on Co, Cu, Fe, Mn, Mo, Ni, and Zn in soil-plant system, the present paper: (a) overviews the status in soils and their uptake, transport, and significance in plants; (b) critically discusses their elevated level-mediated toxicity to both plant growth/development and cell/genome; (c) briefly cross talks on the significance of potential interactions between previous plant-beneficial heavy metal ions in plants; and (d) highlights so far unexplored aspects in the current context.

Essential roles and hazardous effects of nickel in plants

With the world's ever increasing human population, the issues related to environmental degradation of toxicant chemicals are becoming more serious. Humans have accelerated the emission to the environment of many organic and inorganic pollutants such as pesticides, salts, petroleum products, acids, heavy metals, etc. Among different environmental heavy-metal pollutants, Ni has gained considerable attention in recent years, because of its rapidly increasing concentrations in soil, air, and water in different parts of the world. The main mechanisms by which Ni is taken up by plants are passive diffusion and active transport. Soluble Ni compounds are preferably absorbed by plants passively, through a cation transport system; chelated Ni compounds are taken up through secondary, active-transport-mediated means, using transport proteins such as permeases. Insoluble Ni compounds primarily enter plant root cells through endocytosis. Once absorbed by roots, Ni is easily transported to shoots via the xylem through the transpiration stream and can accumulate in neonatal parts such as buds, fruits, and seeds. The Ni transport and retranslocation processes are strongly regulated by metal-ligand complexes (such as nicotianamine, histidine, and organic acids) and by some proteins that specifically bind and transport Ni. Nickel, in low concentrations, fulfills a variety of essential roles in plants, bacteria, and fungi. Therefore, Ni deficiency produces an array of effects on growth and metabolism of plants, including reduced growth, and induction of senescence, leaf and meristem chlorosis, alterations in N metabolism, and reduced Fe uptake. In addition, Ni is a constituent of several metallo-enzymes such as urease, superoxide dismutase, NiFe hydrogenases, methyl coenzyme M reductase, carbon monoxide dehydrogenase, acetyl coenzyme-A synthase, hydrogenases, and RNase-A. Therefore, Ni deficiencies in plants reduce urease activity, disturb N assimilation, and reduce scavenging of superoxide free radical. In bacteria, Ni participates in several important metabolic reactions such as hydrogen metabolism, methane biogenesis, and acetogenesis. Although Ni is metabolically important in plants, it is toxic to most plant species when present at excessive amounts in soil and in nutrient solution. High Ni concentrations in growth media severely retards seed germinability of many crops. This effect of Ni is a direct one on the activities of amylases, proteases, and ribonucleases, thereby affecting the digestion and mobilization of food reserves in germinating seeds. At vegetative stages, high Ni concentrations retard shoot and root growth, affect branching development, deform various plant parts, produce abnormal flower shape, decrease biomass production, induce leaf spotting, disturb mitotic root tips, and produce Fe deficiency that leads to chlorosis and foliar necrosis. Additionally, excess Ni also affects nutrient absorption by roots, impairs plant metabolism, inhibits photosynthesis and transpiration, and causes ultrastructural modifications. Ultimately, all of these altered processes produce reduced yields of agricultural crops when such crops encounter excessive Ni exposures.