Combined impact of short-term phosphorus deficiency and microplastic contamination on tomato mineral elements,...

Microplastic (MP) contamination is expected to affect nearly all plants on Earth in the coming decades. Understanding how MP interacts with existing abiotic stresses is therefore critical. In this study, we investigated the combined effects of phosphorus deficiency (-P) and MP contamination (polyethylene microspheres; 200-9900 μm at 50 mg L^-1) on tomato physiology. Plants were grown hydroponically under four treatments: control (+P/C), phosphorus deficiency (-P/C), MP exposure (+P/MP), and combined stress (-P/MP). After 38 days of growth (24 under -P and 14 with MP exposure) root exudates were collected over 4 h, and plants were harvested. Chlorophyll fluorescence parameters were assessed, and elemental composition of shoots and roots was analyzed via ICP-MS. Root exudates were examined for carboxylates, total organic carbon, proteins, and phenolics. Root exudation was mainly influenced by -P, with no additional effects observed under -P/MP. Ca root content increased significantly in both MP treatments (+P/MP, -P/MP). Interestingly, the -P/MP treatment reduced the -P-induced accumulation of Fe, Zn, and Mo. While + P/MP alone had no effect on chlorophyll fluorescence parameters, the combined stress (-P/MP) significantly mitigated the negative effects of -P on all photosynthetic traits. These findings highlight the importance of studying interactive effects of emerging pollutants with nutrient stresses to better predict plant responses in future environments.