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High concentrations of Cd can inhibit growth and reduce the activity of the photosynthetic apparatus in plants. In several plant species, aldo-keto reductases (AKRs) have been shown to enhance tolerance to various abiotic stresses by scavenging cytotoxic aldehydes; however, few AKRs have been reported to enhance Cd stress tolerance. In this study, the gene IbAKR was isolated from sweet potato. The relative expression levels of IbAKR increased significantly (approximately 3-fold) after exposure to 200 mmol·L−1 CdCl2 or 10 mmol·L−1 H2O2. A subcellular localization assay showed that IbAKR is predominantly located in the nucleus and cytoplasm. IbAKR-overexpressing tobacco plants showed higher tolerance to Cd stress than wild-type (WT). Transgenic lines showed a significant ability to scavenge malondialdehyde (MDA) and methylglyoxal (MG). In addition, proline content and superoxide dismutase activity were significantly higher and H2O2 levels were significantly lower in the transgenic plants than in the WT. Quantitative real-time PCR analysis showed that the reactive oxygen species (ROS) scavenging genes encoding guaiacol peroxidase (GPX), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR) and peroxidase (POD) were significantly upregulated in transgenic plants compared to WT under Cd stress. These findings suggest that overexpressing IbAKR enhances tolerance to Cd stress via the scavenging of cytotoxic aldehydes and the activation of the ROS scavenging system.

Melatonin has emerged as a research highlight regarding its important role in regulating plant growth and the adaptation to the environmental stresses. In this study, we investigated how melatonin prevented the cadmium toxicity to wheat seedlings. The results demonstrated that cadmium induced the expression of melatonin biosynthesis-related genes and cause a significant increase of endogenous melatonin level. Melatonin treatment drastically alleviated the cadmium toxicity, resulting in increased plant height, biomass accumulation, and root growth. Cadmium and senescence treatment significantly increased the endogenous level of hydrogen peroxide, which was strictly counterbalanced by melatonin. Furthermore, melatonin treatment caused a significant increase of GSH (reduced glutathione) content and the GSH/GSSG (oxidized glutathione) ratio. The activities of two key antioxidant enzymes, ascorbate peroxidase (APX) and superoxide dismutase (SOD), but not catalase (CAT) and peroxidase (POD), were specifically improved by melatonin. Additionally, melatonin not only promoted the primary root growth, but also drastically enhanced the capacity of the seedling roots to degrade the exogenous hydrogen peroxide. These results suggested that melatonin played a key role in maintaining the hydrogen peroxide homeostasis, via regulation of the antioxidant systems. Conclusively, this study revealed a crucial protective role of melatonin in the regulation of cadmium resistance in wheat.

Background This study assessed the effects of 24-epibrassinolide (EBL, 10 –7 M) and silicon (2 mM) on the alleviation of cadmium (Cd, 150 mg L –1 ) toxicity in Pisum sativum L. seedlings via the modulation of growth, antioxidant defense, glyoxalase system, and nutrient uptake. Results Shoot and root lengths declined by 46.43% and 52.78%, respectively, following Cd stress. Shoot and root dry weights also declined with Cd toxicity. Biochemical and physiological aspects exhibit significant decline including total chlorophyll (33.09%), carotenoid (51.51%), photosynthetic efficiency (32.60%), photochemical quenching (19.04%), leaf relative water content (40.18%), and gas exchange parameters (80.65%). However, EBL or Si supplementation alone or in combination modulates the previously mentioned parameters. Cadmium stress increased proline and glycine betaine (GB) contents by 4.37 and 2.41-fold, respectively. Exposure of plants to Cd stress increased the accumulation of H 2 O 2 , malondialdehyde content, electrolyte leakage, and methylglyoxal, which declined significantly with EBL and Si supplementation, both individually and in combination. Similarly, Cd stress adversely affected enzymatic and non-enzymatic antioxidants, but EBL and/or Si supplementation maintained antioxidant levels. Glyoxalase I (GlyI) accumulated after Cd stress and increased further with the application of EBL and Si. However, GlyII content declined after Cd stress but increased with supplementation of EBL and Si. Cadmium accumulation occurred in the following order: roots > shoots>leaves. Supplementation with EBL and Si, individually and in combination reduced Cd accumulation and enhanced the uptake of macronutrients and micronutrients in shoots and roots, which declined with Cd toxicity. Conclusion The application of 24-EBL and Si, individually and in combination, alleviated the adverse effects of Cd by improving growth, biochemical parameters, nutrient uptake, osmolyte accumulation, and the anti-oxidative defense and glyoxalase systems in Pisum sativum seedlings.

The heavy metal cadmium (Cd) is a widespread environmental contaminant with harmful effects on living cells. In plants, phytochelatin (PC)-dependent Cd detoxification requires that PC–Cd complexes are transported into vacuoles. Here, it is shown that Arabidopsis thaliana seedlings defective in the ABCC transporter AtABCC3 (abcc3) have an increased sensitivity to different Cd concentrations, and that seedlings overexpressing AtABCC3 (AtABCC3ox) have an increased Cd tolerance. The cellular distribution of Cd was analysed in protoplasts from abcc3 mutants and AtABCC3 overexpressors grown in the presence of Cd, by means of the Cd-specific fluorochromes 5-nitrobenzothiazole coumarin (BTC-5N) and Leadmium™ Green AM dye. This analysis revealed that Cd is mostly localized in the cytosol of abcc3 mutant protoplasts whereas there is an increase in vacuolar Cd in protoplasts from AtABCC3ox plants. Overexpression of AtABCC3 in cad1-3 mutant seedlings defective in PC production and in plants treated with L-buthionine sulphoximine (BSO), an inhibitor of PC biosynthesis, had no effect on Cd tolerance, suggesting that AtABCC3 acts via PCs. In addition, overexpression of AtABCC3 in atabcc1 atabcc2 mutant seedlings defective in the Cd transporters AtABCC1 and AtABCC2 complements the Cd sensitivity of double mutants, but not in the presence of BSO. Accordingly, the level of AtABCC3 transcript in wild type seedlings was lower than that of AtABCC1 and AtABCC2 in the absence of Cd but higher after Cd exposure, and even higher in atabcc1 atabcc2 mutants. The results point to AtABCC3 as a transporter of PC–Cd complexes, and suggest that its activity is regulated by Cd and is co-ordinated with the activity of AtABCC1/AtABCC2.

Key message The OsPCS2 exhibits root- and shoot-specific differential ratios of alternatively spliced transcripts in indica rice under Cd stress, and plays role in Cd and As stress tolerance and accumulation. Enzymatic activity of phytochelatin synthase (PCS) in plant produces phytochelatins, which help in sequestration of heavy metal(loid)s inside the cell vacuole to alleviate toxicity. Here we report that among the two PCS genes— OsPCS1 and OsPCS2 in indica rice ( Oryza sativa ) cultivar, the OsPCS2 produces an alternatively spliced OsPCS2b transcript that bears the unusual premature termination codon besides the canonically spliced OsPCS2a transcript. Root- and shoot-specific differential ratios of alternatively spliced OsPCS2a and OsPCS2b transcript expressions were observed under cadmium stress. Saccharomyces cerevisiae cells transformed with OsPCS2a exhibited increased cadmium (Cd) and arsenic (As) tolerance and accumulation, unlike the OsPCS2b transformed yeast cells. An intron-containing hairpin RNA-mediated gene silencing was carried out in endosperm-specific manner for efficient down-regulation of OsPCS genes in rice grains. Analysis of the transgenic rice lines grown under metal(loid) stress revealed almost complete absence of both OsPCS1 and OsPCS2 transcripts in the developing seeds coupled with the significant reduction in the content of Cd (~51%) and As (~35%) in grains compared with the non-transgenic plant. Taken together, the findings indicate towards a crucial role played by the tissue-specific alternative splicing and relative abundance of the OsPCS2 gene during heavy metal(loid) stress mitigation in rice plant.

Key message S elenium nanoparticles reduce cadmium absorption in tomato roots, mitigating heavy metal effects. SeNPs can efficiently help to enhance growth, yield, and biomolecule markers in cadmium-stressed tomato plants. In the present study, the effects of selenium nanoparticles (SeNPs) were investigated on the tomato plants grown in cadmium-contaminated soil. Nanoparticles were synthesized using water extract of Nigella sativa and were characterized for their size and shape. Two application methods (foliar spray and soil drench) with nanoparticle concentrations of 0, 100, and 300 mg/L were used to observe their effects on cadmium-stressed plants. Growth, yield, biochemical, and stress parameters were studied. Results showed that SeNPs positively affected plant growth, mitigating the negative effects of cadmium stress. Shoot length (SL), root length (RL), number of branches (NB), number of leaves per plant (NL), and leaf area (LA) were significantly reduced by cadmium stress but enhanced by 45, 51, 506, 208, and 82%, respectively, by soil drench treatment of SeNPs. Similarly, SeNPs increased the fruit yield (> 100%) and fruit weight (> 100%), and decreased the days to fruit initiation in tomato plants. Pigments were also positively affected by the SeNPs, particularly in foliar treatment. Lycopene content was also enhanced by the addition of NPs (75%). Furthermore, the addition of SeNPs improved the ascorbic acid, protein, phenolic, flavonoid, and proline contents of the tomato plants under cadmium stress, whereas stress enzymes also showed enhanced activities under cadmium stress. It is concluded from the present study that the addition of selenium nanoparticles enhanced the growth and yield of Cd-stressed plants by reducing the absorption of cadmium and increasing the stress management of plants.

We examined effects of methyl jasmonate (MeJ), with and without N, for the alleviation of the adverse effects of 150 mg kg−1 CdCl2 stress in mentholmint (Mentha arvensis) plants. Exposure of mentholmint plants to Cd stress reduced morphological growth parameters, photosynthetic attributes, chlorophyll content and mineral nutrient assimilation rate. Cd stress significantly increased endogenous leaf and root Cd content by 67.10% and 83.05%, respectively, electrolyte leakage by 67.26%, hydrogen peroxide (H2O2) by 56.66% and malondialdehyde content by 53.97% over that of the control. Cd stress upregulated activities of antioxidant enzymes and increased osmolyte concentration. Application of 1 µM MeJ to Cd-stressed plants partially alleviated the Cd-induced oxidative stress; however, co-application of MeJ with inorganic N reversed the detrimental effects more than did MeJ or N alone. Combined application of MeJ + N further elevated the osmolyte levels and markedly increased mineral nutrient contents and nitrogen use efficiency. MeJ + N significantly reduced the production of reactive oxygen species (ROS) directly or indirectly through higher stimulation of ROS-scavenging enzymes and decreased the root-to-shoot Cd rate of translocation. Cd-induced stomatal inhibition was recovered by MeJ and N. Our study demonstrated the regulatory role of MeJ and N in overcoming Cd stress in mentholmint plants. The study is the first report of regulatory interaction of the exogenous phytohormone (MeJ) with inorganic nutrient (N) for enhancing Cd stress tolerance in mentholmint plants, the same concept can be used for remediation of toxic metal/metalloids in agricultural production.

Photosynthesis plays an essential role in plant growth and crop yield, and the mechanisms of the effects of cadmium (Cd) on photosynthetic performance require more attention. The acute toxicity of Cd in soil to the photosynthetic capacity of was evaluated using gas exchange parameters, / curves, light response curves, and chlorophyll fluorescence transients after exposure to elevated Cd concentrations (0, 10, 20, 50, 70, and 100 mg kg ) for a 3-month period. The results indicated that leaf Cd concentration in increased with the strength of soil Cd stress and ranged from 4.9 to 15.8 μg g DW. The accumulation of leaf Cd severely restricted photosynthesis and its non-stomatal limitation in regulating the photosynthetic performance of . The leaf chloroplasts at 10 and 20 mg kg Cd concentrations showed no noticeable change, but the chlorophyll content significantly decreased by 9.0-20.4% at 50-100 mg kg Cd concentrations. The Cd treatments also decreased plant ribulose-1,5-bisphosphate (RuBP) activity ( ) and regeneration capacity ( ), triose phosphate utilization ( ), light-saturated photosynthesis ( ), apparent quantum yield ( ), light saturation point ( ), and dark respiration ( ), but Cd treatment increased the light compensation point ( ). The shape of chlorophyll fluorescence transients in leaves was altered under different Cd treatments. The increased OJ phase and the decreased IP phase in fluorescence induction curves suggested that Cd toxicity inhibited both light use efficiency and photodamage avoidance ability. These results suggested that the decrease in photosynthesis through exposure to Cd may be a result of the decrease in leaf chlorophyll content, Rubisco activity, and RuBP regeneration, inhibition of triose phosphate utilization, reduction of the ability to use light and provide energy, and restrictions on electron transport in PSII.

Cadmium (Cd) can harm the yield and quality of vegetables, threatening food safety. Essential microelements such as iron are crucial for plant growth and can help alleviate heavy metal stress. Recently, nanoparticles have been studied as eco-friendly solutions for mitigating heavy metal stress in plants. In the present study, iron nanoparticles (FeNPs) at 0, 100, and 300 mg/L were applied as soil drenches and foliar sprays to tomato plants under cadmium stress. A comparison was made between the application methods of FeNPs by evaluating the growth parameters of tomato plants, including shoot length (SL), root length (RL), number of branches (NB), number of leaves per plant (NL), and leaf area (LA), as well as by assessing biochemical and antioxidant enzyme parameters. In the Cd stress treatment, the protein content decreased by 24.71%, and the phenolic and flavonoid content of the tomato plants also decreased due to cadmium stress, with levels decreasing from 16.07 to 6.9 µg and from 0.36 to 0.16 µg, respectively. Compared with the soil drench, 100 mg/L FeNPs significantly improved the parameters of Cd-stressed plants when used as a foliar spray, leading to increases in shoot length, root length, fruit weight, number of fruits, number of leaves, and number of branches by 42%, 66%, 24%, 66%, 173%, and 45%, respectively. Tomato plants treated with this spray presented increased carotenoid and lycopene contents. FeNP foliar spray also reduced Cd accumulation in plant tissues. This technique shows promise in alleviating Cd stress in vulnerable vegetable plants such as tomatoes.

This research examines the influence of exogenous indole-3-acetic acid (IAA) on growth parameters and cadmium stress resistance in Sorghum bicolor (L. Moench). The plants were grown in pots, each filled with 4.5 kg of sand. After 21 days, root treatment with indole-3-acetic acid (IAA) was applied using five concentrations (0, 50, 100, 150, and 200 µM) under three cadmium (Cd) levels (0, 40, and 80 ppm). Applied Cadmium stress significantly reduced plant growth, with reductions in root length (12.73–15.88%), shoot length (17.60–19.25%), and plant height (10.62–14.88%). All growth parameters were improved with the application of 200 µM IAA, increasing root length (20.25–28.25%), shoot length (35.68–45.68%), and plant height (20.37%). The highest level of cadmium stress (80 ppm) was the most detrimental, while the 200 µM IAA treatment produced the most favorable results. Under cadmium stress, IAA application reduced the uptake of Na + , K + , and Ca 2+ ions by 7.69–9.52%, 3.70–7.31%, and 6.66–7.69%, respectively, as well as Cd 2+ by 2.50–5.26%. Despite these reductions, IAA application significantly enhanced antioxidant activities, including catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD). At 200 µM IAA, antioxidant enzyme activities were increased by 4.65% (SOD), 8.82% (POD), 10.06% (CAT), and 17.9% ascorbate peroxidase (APX). The treatment also boosted chlorophyll content (17.46–22.85%), while reducing oxidative stress markers such as H 2 O 2 (29.4–40.8%) and malondialdehyde (38.9–42.1%). These findings suggest that IAA effectively mitigates cadmium-induced stress by improving growth parameters and physiological responses. Future research should explore the molecular mechanisms underlying IAA-mediated cadmium stress alleviation.