Nickel tolerance and phytoremediation potential of quinoa are modulated under salinity: multivariate comparison of physiological and biochemical attributes

The impact of nickel on plant growth and oxidative balance

This review summarizes the impact of nickel (Ni) in hydroponics on the growth, basic biochemical parameters and oxidative balance in angiosperms using data from 66 papers (and 181 treatments). Generally, changes in biomass, pigments (chlorophylls and carotenoids) and proteins were negative when comparing concentration (≤100 and >100 μM) and time (≤14 and >14 days). However, we could deduce a higher tolerance to Ni excess in dicots than in monocots. Growth and basic metabolites were often significantly positively correlated. In contrast to proteins, amino acids were positively affected by Ni, indicating proline accumulation and/or protein catabolism. The increase in hydrogen peroxide (H2O2) content was stimulated by time and Ni concentration, and it is higher in dicots and usually negatively correlated with basic metabolites. An increase in Ni concentration stimulates the increase of thiols, but a longer exposure has a neutral or negative effect. On the contrary, the amount of vitamin C (ascorbic acid) is positively influenced by the dose of Ni in roots and the duration of excess Ni in shoots, which points to dynamic changes of this antioxidant in individual organs. Soluble phenols were not as affected, but their importance appears especially in shoots during long-term exposure to Ni with a simultaneous increase in H2O2 content, confirming their antioxidative role. We emphasize that due to the significant quantitative variability in the published studies, we analyze the presented parameters as a percentage change.

Multivariate characterization of biochemical and physiological attributes of quinoa (Chenopodium quinoa Willd.) genotypes exposed to nickel stress: implications for phytoremediation

Nickel (Ni) is an essential element for plants; however, excessive uptake of Ni causes phytotoxicity in plants. The phytotoxic effects of Ni on the growth of quinoa and the underlaying mechanisms for Ni tolerance and phytoremediation are unknown. Hence, the present study investigated Ni tolerance and accumulation potential of two quinoa genotypes (Puno and Vikinga). Both genotypes were exposed to Ni (0, 100, 200, 300, and 400 μM) in half-strength Hoagland nutrient solution for three weeks. Results revealed that shoot and root lengths, biomass, stomatal conductance, and chlorophyll contents were decreased with the increase of Ni concentration. Excessive uptake of Ni resulted in the limited uptake of K by root and its translocation to shoot. Ni caused oxidative stress in plants by overproduction of H2O2 leading to lipid peroxidation of cell membranes. Genotype Puno showed greater tolerance to Ni than Vikinga based on tolerance index, lower bioconcentration factor, and translocation factor. Greater tolerance of Puno was mainly attributed to improved physiological responses and amelioration of oxidative stress by induction of antioxidant enzymes such as peroxidase (POD), catalase (CAT), superoxide dismutase (SOD), and ascorbate peroxidase (APX). It was revealed through multivariate analysis that Ni had strong negative correlations with growth and physiological attributes and positive associations with oxidative stress attributes. The study demonstrated genotypic variation in response to varying Ni concentrations and Puno performed better than Vikinga for phytostabilization of Ni-contaminated soils.

Assessment of lithium bioaccumulation by quinoa (Chenopodium quinoa willd.) and its implication for human health

Lithium (Li) is the lightest alkali metal and 27th most abundant element in the earth crust. In traces, the element has medicinal value for various disorders in humans, however, its higher concentrations may lead to treatment-resistant depression and altered thyroid functioning. Quinoa (Chenopodium quinoa) has gained popularity owing to its halophytic nature and its potential use as an alternative to the traditional staple foods. However, quinoa response to Li-salt in terms of growth, Li accumulation potential and health risks associated with consumption of the quinoa seeds grown on Li-contaminated soils has not been explored yet. During this study, quinoa was exposed to various concentrations of Li (0, 2, 4, 8 and 16 mM) at germination as well as seedling stages. The results showed that seed germination was the highest (64% higher than control) at Li concentration of 8 mM. Similarly, at 8 mM doses of Li shoot length, shoot dry weight, root length, root dry weight and grain yield were increased by 130%, 300%, 244%, 858% and 185% than control. It was also revealed that Li increased the accumulation of calcium and sodium in quinoa shoots. Carotenoids contents were increased, but chlorophyll contents remained un-changed under Li application. The activities of antioxidants viz. Peroxide dismutase, catalase and super oxide dismutase were also increased with an increase in the levels of Li in the soil. Estimated daily intake and hazard quotient of Li in quinoa were less than the threshold level. It was concluded that Li concentration of 8 mM is useful for quinoa growth and it can be successfully grown on Li contaminated soils without causing any human health risks.

Yield, phenology and triterpene saponins in Colombian quinoa

Exploring yield, phenology and their relationship with secondary metabolites in seeds provides a fundamental analysis that expands knowledge on the nutritional quality of seeds and the effect on productive potential. This knowledge is fundamental when improving or selecting nutritionally important crops, including Chenopodium quinoa Willd, which has excellent nutritional properties and contributes to global food security. This species contains saponins, a metabolite that imparts a bitter taste and can be highly toxic to consumers in large quantities. Therefore, the identification and selection of genotypes according to their saponin contents and outstanding agronomic characteristics are fundamental objectives for the genetic improvement programs of these species. Therefore, the objective of this research was to evaluate the characteristics of the grain, the phenology and the saponin content of 30 C. quinoa accessions with an aim to select or relate genotypes according to their yield and grain quality. The accessions were sown using randomized complete blocks (RCB) with nine repetitions for each material. Seven FAO-defined descriptors were evaluated to characterize the grain and physiological maturity. Saponin was extracted using microwave, and the quantification was done with high-performance liquid chromatography (HPLC) which a UV-VIS detector at 277 nm wavelength. The accessions were classified according to their phenology: semi-late (56.7%), late (36.7%), and semi-early (3.3%). The total triterpene saponin content varied from 0.018 to 0.537%. The multivariate and cluster analyses formed groups of accessions with good yields (>62.02 g of seeds per plant) and desirable grain morphological characteristics. The more suitable accessions for the production of saponins are Quinoa semiamarga (0.537%), Quinoa peruana (0.412%) and Amarilla de maranganí (0.305%). Quinoa real and Quinoa primavera are more suitable for food products, which can be used as parents in future quinoa genetic improvement programs in Colombia.

Silicon-nanoparticles doped biochar is more effective than biochar for mitigation of arsenic and salinity stress in Quinoa: Insight to human health risk assessment

The increasing contamination of soil with arsenic (As), and salinity has become a menace to food security and human health. The current study investigates the comparative efficacy of plain biochar (BC), and silicon-nanoparticles doped biochar (SBC) for ameliorating the As and salinity-induced phytotoxicity in quinoa (Chenopodium quinoa Willd.) and associated human health risks. Quinoa was grown on normal and saline soils (EC_e 12.4 dS m^-1) contaminated with As (0, 20 mg kg^-1) and supplemented with 1% of BC or SBC. The results demonstrated that plant growth, grain yield, chlorophyll contents, and stomatal conductance of quinoa were decreased by 62, 44, 48, and 66%, respectively under the blended stress of As and salinity as compared to control. Contrary to this, the addition of BC to As-contaminated saline soil caused a 31 and 25% increase in plant biomass and grain yield. However, these attributes were increased by 45 and 38% with the addition of SBC. The H₂O₂ and TBARS contents were enhanced by 5 and 10-fold, respectively under the combined stress of As and salinity. The SBC proved to be more efficient than BC in decreasing oxidative stress through overexpressing of antioxidant enzymes. The activities of superoxide dismutase, peroxidase, and catalase were enhanced by 5.4, 4.6, and 11-fold with the addition of SBC in As-contaminated saline soil. Contamination of grains by As revealed both the non-carcinogenic and carcinogenic risks to human health, however, these effects were minimized with the addition of SBC. As accumulation in grains was decreased by 65-fold and 25-fold, respectively for BC and SBC in addition to As-contaminated saline soil. The addition of SBC to saline soils contaminated with As for quinoa cultivation is an effective approach for decreasing the food chain contamination and improving food security. However, more research is warranted for the field evaluation of the effectiveness of SBC in abating As uptake in other food crops cultivated on As polluted normal and salt-affected soils.