Bioremediation of potentially toxic elements of sewage sludge using sunflower (Heliantus annus L.) in greenhouse and field conditions

Biochemical properties and pigment contents of Satureja genotypes affected by plant growth regulators and temperature stress

There is little data, to our knowledge, on the biochemical properties of different Satureja sp. genotypes affected by plant growth regulators (PGR) under temperature stress. A split plot research on the basis of a complete randomized block design with three replicates examining temperature stress (planting dates, 8th of April, May and June) (main factor), and the factorial combination of plant growth regulators (PGR, control (CO), gibberellic acid (GA), fertilization (MI), and amino acid (A)), and genotypes (Khuzestani, Mutika, and Bakhtiari) on plant biochemical properties, was conducted. Plant pigment contents (chlorophyll a, and b and carotenoids (car)), antioxidant activity (catalase (CAT), ascorbate peroxidase (APX) and guaiacol peroxidase (GP)), and leaf protein were determined. Treatments significantly and differently affected the genotypes performance. PD3 and PD1resulted in significantly higher activity of APX (0.059 U. mg-1) and GP (0.190 U. mg-1), respectively (P ≤ 0.05). Temperature stress significantly affected plant CAT activity (U. mg-1) at PD1 (0.084) and PD3 (0.820). Higher temperature significantly enhanced leaf Pro, MI increased plant APX (0.054) and CAT activities (0.111 U. mg-1) significantly, and GA resulted in the highest and significantly different GP activity (0.186 U. mL-1). Treatments T1 and T3 significantly enhanced Chla and Car content, and MI resulted in significantly higher Chlb content (0.085 mg g-1 leaf fresh weight). Car and CAT are the two most sensitive biochemical traits under temperature stress and can more effectively regulate Satureja growth and activity. It is possible to alleviate temperature stress on Satureja biochemical properties by the tested PGR.

Tryptophan Seed Treatment Improves Morphological, Biochemical, and Photosynthetic Attributes of the Sunflower under Cadmium Stress

Tryptophan, as a signal molecule, mediates many biotic and environmental stress-induced physiological responses in plants. Therefore, an experiment was conducted to evaluate the effect of tryptophan seed treatment in response to cadmium stress (0, 0.15, and 0.25 mM) in sunflower plants. Different growth and biochemical parameters were determined to compare the efficiency of the treatment agent. The results showed that cadmium stress reduced the growth attributes, including root and shoot length, dry and fresh weight, rate of seed germination, and the number of leaves. Cadmium stress also significantly reduced the contents of chlorophyll a, b, and total chlorophyll, carotenoid contents, phenolics, flavonoids, anthocyanin, and ascorbic acid. Whereas cadmium stress (0.15 and 0.25 mM) enhanced the concentrations of malondialdehyde (45.24% and 53.06%), hydrogen peroxide (-11.07% and 5.86%), and soluble sugars (28.05% and 50.34%) compared to the control. Tryptophan treatment decreased the effect of Cd stress by minimizing lipid peroxidation. Seed treatment with tryptophan under cadmium stress improved the root (19.40%) and shoot length (38.14%), root (41.90%) and shoot fresh weight (13.58%), seed germination ability (13.79%), average leaf area (24.07%), chlorophyll b (51.35%), total chlorophyll (20.04%), carotenoids (43.37%), total phenolic (1.47%), flavonoids (19.02%), anthocyanin (26.57%), ascorbic acid (4%), and total soluble proteins (12.32%) compared with control conditions. Overall, the tryptophan seed treatment showed positive effects on sunflower plants' growth and stress tolerance, highlighting its potential as a sustainable approach to improve crop performance.

Chromium (VI) bioremoval from contaminated wastewater using Pseudomonas aeruginosa ATHA23 producing biofilm supported on clinoptilolite

More has yet to be investigated on the increased efficiency of microbes for the removal of heavy metals from industrial wastewaters. The objective was to determine the Cr (VI) bioabsorption and bioreduction ability of biofilm-producing bacteria supported on clinoptilolite from contaminated aqueous solutions. Chromium (VI)-tolerant bacteria, namely Pseudomonas aeruginosa ATHA23, were identified by biochemical methods and 16S rDNA sequencing and were deposited in NCBI (accession number: KF680991). Preparation of clinoptilolite, bacterial growth and isolation, biofilm production including extracellular polysaccharides (EPS) and Cr (VI) removal efficiency, affected by the experimental treatments, were investigated. The use of FTIR characterized clinoptilolite properties with and without biofilm in the presence and absence of Cr (IV). Higher Cr (VI) levels in the bacterial growth medium, increased EPS production with the highest value (0.171 mg L^-1), produced 18 h after treating the bacteria with Cr (VI) (100 mg L^-1). However, in the absence of Cr (VI), EPS significantly decreased to 0.117 mg L^-1. Plackett-Burman and Taguchi statistical analyses were used to optimize the experimental treatments affecting the removal efficiency of Cr (VI). Among the anions (nitrate, sulfate, and chloride), sulfate decreased Cr removal efficiency. The absorption data were best fitted to the pseudo-second order, and the data of Cr adsorption by clinoptilolite-biofilm were also better fitted to Freundlich isotherm model. The Cr (VI) bioremediation potential of P. aeruginosa ATHA23 by the production of biofilm supported on clinoptilolite has been shown for the first time, which is of significance for the environment and the industry.

Photosynthetic response, antioxidase activity, and cadmium uptake and translocation in Monochoria korsakowii with cadmium exposure

To identify the tolerance mechanisms of wetland plants exposed to heavy metal, a hydroponic experiment was used to investigate variations in photosynthetically physiological parameters and antioxidant enzyme activities in leaves of Monochoria korsakowii exposed to 0.05, 0.15, 0.30, and 0.45 mM Cd²⁺ for 7 d. The Cd²⁺ concentrations in the plant roots, stems, and leaves were also investigated. Cd²⁺ exposure significantly decreased the total chlorophyll content, net photosynthetic rate, intercellular carbon dioxide concentration, and stomatal conductance, while stomatal limitation value had the opposite trend (P < 0.05). During Cd²⁺ stress, ascorbate peroxidase activity significantly increased (P < 0.05). The translocation factor for Cd²⁺ was significantly lower than that of the control, and both were less than 1 (P < 0.05). Cd²⁺ stress damaged the photosynthetic apparatus in the leaves. During Cd²⁺ stress, M. korsakowii alleviated oxidative stress by increasing the activities of antioxidant enzymes, such as APX. Under 0.45 mM Cd²⁺ stress, increased heat dissipation was responsible for alleviating the photooxidative damage to photosynthetic organs in the leaves. Meanwhile, the majority of Cd²⁺ was immobilized in the roots, thus alleviating excessive Cd²⁺ phytotoxicity in the aboveground parts. Generally, M. korsakowii has potential application in the phytoremediation of low-cadmium-polluted water.

Physiological and Transcriptomic Comparison of Two Sunflower (Helianthus annuus L.) Cultivars With High/Low Cadmium Accumulation

The toxic heavy metal cadmium (Cd) is easily absorbed and accumulated in crops and affects human health through the food chains. Sunflower (Helianthus annuus L.) is a globally important oil crop. In this study, two sunflower cultivars 62\3 (high Cd) and JB231AC (low Cd), were chosen to compare physiological and transcriptomic responses at different Cd concentrations (0, 25, 50, and 100 μM). The results showed that JB231AC had better Cd tolerance than 62\3. The contents of H₂O₂ and MDA (malondialdehyde) in 62\3 were lower than that in JB231AC under Cd stress, but the activities of SOD (superoxide dismutase) and POD (peroxidase) in JB231AC were higher than in 62\3, which indicated that JB231AC had a strong ability to remove reactive oxygen species (ROS)-induced toxic substances. Many deferentially expressed ABC (ATP-binding cassette) and ZIP (Zn-regulated transporter, Iron-regulated transporter-like protein) genes indicated that the two gene families might play important roles in different levels of Cd accumulation in the two cultivars. One up-regulated NRAMP (Natural resistance-associated macrophage protein) gene was identified and had a higher expression level in 62\3. These results provide valuable information to further understand the mechanism of Cd accumulation and provide insights into breeding new low Cd sunflower cultivars.