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Beneath the rice paddies of the Kyzylorda region lies a threat that cannot be seen, smelled, or tasted — but one whose consequences accumulate over decades. That threat is cadmium.

Widespread use of phosphate fertilisers, the activity of metallurgical enterprises, and the application of phosphogypsum to saline soils have driven a steady build-up of cadmium in Kazakhstani agricultural land. Cadmium belongs to the highest hazard class: even in trace quantities it disrupts the physiological and biochemical processes of plants, depresses yields, and — once it enters the food chain — causes serious human diseases including kidney failure and osteomalacia.

A research team is tackling this problem head-on through the project "Cadmium Toxicity in Rice Plants and the Use of Physicochemical Methods to Enhance Resistance." Funded under the priority direction "Ecology, Environment and Rational Use of Natural Resources" for 2025–2027. The team comprises three doctors of science, one PhD doctoral candidate, and one master's-level researcher.

Rice is a strategically important crop for Kazakhstan. According to the Kazakh Academy of Nutrition, the country's annual rice requirement stands at 132,600 tonnes — roughly 8.5 kg per person per year. Kazakhstan has approximately 225,000 hectares of equipped land under rice cultivation, with 175,000 hectares concentrated in the Kyzylorda region alone.

It is precisely these areas where rice grows on saline soils that are simultaneously the most exposed to cadmium contamination. Research shows that intensive use of phosphate fertilisers can raise soil cadmium concentrations to 300 mg/kg dry weight. The metal enters rice plants through roots via the xylem, migrates to leaves, and ultimately accumulates in grain.

At the plant level, cadmium induces oxidative stress, suppresses photosynthesis, impairs nutrient transport, and can lead to tissue death. At the human level, regular consumption of high-cadmium rice over time leads to progressive bioaccumulation in the kidneys and bones. The stakes are not merely agronomic — they are a matter of food safety.

The project pursues a single overarching goal — identifying the most effective methods for reducing cadmium toxicity in rice — through three simultaneous research directions.

Direction one: varietal screening. Rice varieties cultivated in Kazakhstan are systematically compared for cadmium tolerance. The plant material is drawn from the collection of the Kazakhstani Research Institute of Rice Growing named after Ibray Zhakhayev in Kyzylorda. Growth parameters (plant length, biomass accumulation), photosynthetic pigment content, relative water content (RWC), and proline levels are analysed across varieties. The outcome is a classification of varieties into relatively tolerant and sensitive groups — the foundation for all subsequent work.

Direction two: growth regulators. Three plant growth regulators are tested for their ability to counteract cadmium toxicity: "Epin-Extra" (a solution of epibrassinolide, a brassinosteroid), "Zircon" (a solution of hydroxycinnamic acids), and "Potassium Humate" (containing humic and fulvic acids, NPK, and mineral elements including calcium, magnesium, iron, and manganese). Brassinosteroids are known to activate cell division and elongation. Hydroxycinnamic acids, as phenolic compounds, exert antioxidant and protective activity against oxidative stress. Potassium humate regulates nitrogen and carbon metabolism and influences physiological processes through gene expression changes. Preliminary data from the research group show that "Potassium Humate" and "Zircon" produced the best results across most varieties under cadmium stress — a finding that now forms the starting point for systematic optimisation.

Direction three: microwave irradiation. Pre-sowing treatment of seeds with an electromagnetic field in the extremely high frequency (EHF) range is a physical method for priming plant defence mechanisms. The treatment is carried out at the Institute of Nuclear Problems of Belarusian State University, using a frequency of 64–66 GHz, power of 10 mW, and exposure durations of 10 and 20 minutes. Previous experiments by the same facility on other crops demonstrated that EHF treatment activates non-specific stress resistance — a promising precedent for rice under cadmium stress.

The project deploys a well-established suite of analytical methods. Photosynthetic pigment content — chlorophyll a and b, and carotenoids — is measured spectrophotometrically at wavelengths of 665, 649, and 440.5 nm, calculated using the Werner and Wettstein formulas. Proline content is determined by the Bates et al. (1973) method using ninhydrin reagent: proline accumulates as an osmoprotectant under stress, and its reduction in growth-regulator-treated plants compared to cadmium-only controls signals a mitigation of toxic effect. Relative water content is measured by the Schonfeld et al. method. All experiments are conducted in a minimum of three replicates, with results processed using Student's t-test and ANOVA.

The collaboration with the Institute of Nuclear Problems at Belarusian State University is central to the project's physical treatment component. BSU researchers conducting seed irradiation will be listed as co-authors on publications arising from those experiments.

Consultative support is provided by Usenbekov B.N., Candidate of Biological Sciences and Head of the Laboratory of Plant Physiology and Biochemistry at IBBR — a specialist in rice under stress conditions — whose involvement will be reflected in joint publications.

The research group enters this project with a substantial scientific foundation. A predecessor project carried out in 2015–2017 investigated cadmium accumulation across rice organs, its effects on mineral composition, and its interaction with iron deficiency in the soil. That work produced several publications including a paper in BioMed Research International (Scopus Q2). The critical distinction of the present project is its direction: where the earlier work characterised the damage cadmium causes, this project is explicitly oriented toward solutions — finding the most effective chemical and physical means of reducing that damage.

The practical relevance of the project extends across several groups. Farmers and agricultural enterprises in areas with elevated soil cadmium — whether from heavy fertiliser use or proximity to metallurgical sources — will receive evidence-based guidance on variety selection and growth regulator application. State bodies responsible for agricultural policy will gain a scientific basis for decisions on variety registration and food safety standards. The broader scientific community will gain new data on the mechanisms by which brassinosteroids, phenolic compounds, humic acids, and EHF irradiation interact with cadmium stress responses in a major food crop.

Results will be published in international peer-reviewed journals indexed in Scopus and Web of Science.