Maize is diagnosed as a heavy metal (HM) accumulator, while the tolerance mechanism is not sufficiently known. A hydroponic experiment was performed to test the ability of maize plants to tolerate and accumulate Cu. Excess copper treatments (ECu; 5 and 10 μM CuSO₄) considerably reduced plant growth, photosynthetic pigments, ascorbate peroxidase (APX), and guaiacol peroxidase (POD) activity. However, ECu significantly enhanced catalase (CAT) activity. ECu treatments reduced the leaf membrane integrity as indicated by increasing malondialdehyde (MDA) content in leaves. Proline and phenolic contents were considerably increased in maize organelles by ECu toxicity. ECu treatments considerably stimulated free amino acid (FAA) accumulation, total-soluble proteins (TSPs), and K in shoots, whereas these parameters did not change in the roots. Applications of CuSO₄ did not affect the accumulation of total soluble sugars (TSSs) in shoots, while this accumulation enhanced in roots. CuSO₄ treatments significantly increased the Cu concentration and uptake but decreased the Cu translocation factor (TF) and bioaccumulation factor (BF). Structural components such as cell wall components, proteins, lipids, and sugars were affected by ECu stress, as shown by infrared spectroscopy (FT-IR) analysis. These results give a new insight into the strategy, which maize can use to treat the Cu-polluted environment as Cu accumulates within seedling tissues and the seedling can protect itself from ECu stress.

Boron (B) is a fundamental micro-nutrient for plants, while deficiency or excess manipulates growth and leads to quality and yield losses. Excess boron (EB) is more difficult to manage in plants compared to deficiency, where it is irreversible. Several strategies have been developed to mitigate EB stress in plants. This review article abstracts the presence of B, its absorption and transport by plants, functions in plant life, its toxicity, physiological responses to it, recent developments in its toxicity alleviation, and provides recommendations for future studies.

Pomegranate trees are tropical and subtropical shrubs with nutritional benefits and pharmaceutical and therapeutic uses. Antioxidative systems protect the structure and function of cellular membranes. This study demonstrated the connection between oxidative stress generated by excess nanoparticles ZnO (ZnO-NPs) accumulation in pomegranate calli and the involvement of thiol groups and volatile and semi-volatile compounds in alleviating this stress. The effect of the non-enzymatic antioxidant system was studied using callus treated with three levels of ZnO-NPs or bulk particles (ZnO-BPs). With rising ZnO levels in the media, callus growth was gradually decreased by ZnO in both forms (NPs and BPs). Malondialdehyde (MDA) measurements revealed that different concentrations of both forms promoted lipid peroxidation. The supply of both forms had a considerable stimulatory influence on the cysteine (Cys) content in calli. Raised ZnO-NP concentrations increased glutathione (GSH) and non-protein thiols (NPTs) content in calli, but higher ZnO-BP concentrations lowered their content. Conversely, ZnO-NP levels reduced the protein thiols (PTs) content in calli, but ZnO-BP concentrations increased their content. GC-MS analysis was employed to investigate the volatile and semi-volatile chemical profiles within calli following exposure to 0 and 150 μg mL⁻¹ of ZnO in both forms. GC-MS analysis detected 77, 67, and 83 compounds in ZnO-treated calli, of which 14, 16, and 20 with a similarity value greater than 70%, based on a NIST library, were recognized as metabolites for ZnO untreated and NPs- and BPs-treated calli, respectively. Six substances, including five alkanes and one morphinan, showed similarities in metabolite composition between control and NPs- or BPs-treated calli. ZnO-NPs-treated calli contained two alkane compounds only similar to the control, but ZnO-BPs-treated calli had six metabolites, including four alkanes, one carboxylic acid, and one ester. However, eight alkanes were similar within the callus treated with NPs and BPs.

With the scarcity of good quality water, plants like tomatoes will be more susceptible to excess boron (EB) in Mediterranean regions. The effects of EB on the growth, free, semi-bound, and bound boron (B) concentrations, and macromolecules of the Solanum lycopersicum L. cultivar Castle Rock, were investigated in this study. Seedlings were exposed to four levels of EB using boric acid. The results manifested that EB inhibited tomato growth, total water content, and photosynthetic pigments. EB harmed the membrane stability, as seen by increased potassium (K) leakage, UV absorbance metabolites, and electrolyte conductivity (EC) in leaf disc solution. EB raised concentrations of free, semi-bound, and bound forms of B in seedlings. Fourier transform infrared spectroscopy (FTIR) data revealed that EB induced uneven wax deposition, altered the shape of cell walls, and lowered cellulose synthesis in seedlings. EB affected the amide I and amide II indicating damage to the protein pools. These results provide new insights into understanding the specific effects of EB on the functional groups of different macromolecules of tomato seedlings.

There is a growing interest for the utilization of microalgae in the bioremediation of organic pollutants and the use of biomass as a biofuel feedstock. This study investigated the influence of phenol exposure and culture conditions on the phenol removal efficiency, biomass productivity and lipid contents of Tetradesmus obliquus. Plackett-Burman design identified CaCl₂, NaNO₃, and initial phenol concentration as the most important variables affecting on phenol removal. The optimum conditions to maximize biomass productivity, phenol removal and lipid content were determined using the Box-Behnken experimental design as 150.1 mg L⁻¹ phenol, 0.1 g L⁻¹ NaNO₃, and 0.03 g L⁻¹ CaCl₂. Under these conditions, phenol was completely removed from the optimized medium after 3 days and the biomass productivity and lipid content were 19.53 mg L⁻¹ day⁻¹ and 27.85% (w/w) after 10 days, respectively. Phenol treatment promoted algal biomass productivity to ∼1.3-folds and lipid productivity to ∼ 1.6-folds higher than the control treatment without adding phenol (negative control). Additionally, phenol altered the fatty acid methyl ester composition and increased the saturated and polyunsaturated fatty acid contents with concomitant decrease in the monounsaturated fatty acids. The predicted biodiesel characteristics viz. iodine value, cetane number, oxidation stability, kinematic viscosity, and flash point, in the presence of phenol were in accordance with the international standards. Accordingly, the present study indicated that phenol could be effectively bioremediated by T. obliquus with simultaneous promotion of the algal biomass and lipid productivity for biofuel production.

There is a growing interest for the utilization of microalgae in the bioremediation of organic pollutants and the use of biomass as a biofuel feedstock. This study investigated the influence of phenol exposure and culture conditions on the phenol removal efficiency, biomass productivity and lipid contents of Tetradesmus obliquus. Plackett-Burman design identified CaCl₂, NaNO₃, and initial phenol concentration as the most important variables affecting on phenol removal. The optimum conditions to maximize biomass productivity, phenol removal and lipid content were determined using the Box-Behnken experimental design as 150.1 mg L⁻¹ phenol, 0.1 g L⁻¹ NaNO₃, and 0.03 g L⁻¹ CaCl₂. Under these conditions, phenol was completely removed from the optimized medium after 3 days and the biomass productivity and lipid content were 19.53 mg L⁻¹ day⁻¹ and 27.85% (w/w) after 10 days, respectively. Phenol treatment promoted algal biomass productivity to ∼1.3-folds and lipid productivity to ∼ 1.6-folds higher than the control treatment without adding phenol (negative control). Additionally, phenol altered the fatty acid methyl ester composition and increased the saturated and polyunsaturated fatty acid contents with concomitant decrease in the monounsaturated fatty acids. The predicted biodiesel characteristics viz. iodine value, cetane number, oxidation stability, kinematic viscosity, and flash point, in the presence of phenol were in accordance with the international standards. Accordingly, the present study indicated that phenol could be effectively bioremediated by T. obliquus with simultaneous promotion of the algal biomass and lipid productivity for biofuel production.