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Arginine-Dependent Defense Actions in Rice (Oryza Sativa L.) Against Microplastic Contaminated Root Zone

Journal of soil science and plant nutrition 2026
M. S. Najla Alotaibi, Naila Hadayat, Mohamed Alshahrani, Muhammad Irshad, Anees Manzoor, Nahaa M. Alotaibi, FAHAD MOHAMMED ALZUAIBR, Suliman Mohammed Suliman Alghanem, OMAR MAHMOUD ALZOUBI, Jeddi Kaouthar, Saher Nawaz

Summary

Rice plants exposed to high-density polyethylene and polystyrene microplastics suffered reduced growth, lower photosynthesis, and oxidative stress, but treating the root zone with the amino acid L-arginine partially reversed these harms. The finding matters because microplastic contamination of agricultural soils threatens crop yields, and natural compounds like L-arginine could offer low-cost ways to protect food production.

We investigated the rice responses to high-density polyethylene (HDPE) and polystyrene (PS) microplastics and assessed the efficacy of root zone-applied L-arginine in mitigating the microplastic-induced stress. Rice plants were exposed to HDPE and PS microplastics (200 and 400 mg L⁻¹). The ameliorative potential of L-arginine was assessed through recording growth parameters, photosynthetic attributes, chlorophyll content, and biochemical traits. Antioxidant enzyme activities i.e., superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) along arginine allocation within plant tissues were also measured. Microplastics markedly reduced shoot and root biomass, photosynthetic efficiency, and chlorophyll content. PS at 400 mg L⁻¹ (T4) exerted the greatest damage. L-arginine alleviated these impairments by modulating biomass, photosynthetic rate, stomatal conductance, and water-use efficiency. L-arginine treated plants sustained higher protein and osmolyte levels. Malondialdehyde and hydrogen peroxide accumulation were substantially reduced by L-arginine contrary to the microplastic stress. SOD, POD, and CAT activities after L-arginine treatment reinforced antioxidant defense. L-arginine treatment promoted its own allocation within tissues and restricted microplastic accumulation. Multivariate analysis revealed that microplastic stress disrupted physiological homeostasis whereas L-arginine application restored metabolic balance and oxidative stability. Root zone L-arginine effectively enhanced rice resilience and presenting a viable strategy to counteract to environmental pollutants.

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