Effects of microplastic and copper applications on chlorophyll and carotenoid contents in kale and tomato

Microplastics (MP) are important pollutants observed almost everywhere in the ecosphere and threaten agricultural ecosystems due to modern agricultural practices. The MPs change the soil structure and affect plant growth. This study investigated individual and combined effects of MP and copper (Cu) on chlorophyll and carotenoid contents of tomato (Lycopersicon esculentum Mill.) and kale (Brassica oleracea var. acephala DC) plants. Experimental groups were treated with 100 ppm and 500 ppm CuSO₄ and 0.5%, 1.5% and 2.5% MP concentrations. The MPs were obtained by cutting polyethylene films. Chlorophyll a, b, total chlorophyll and carotenoid contents were measured spectrophotometrically and analyzed using one-way ANOVA. In tomato plants, 1.5% MP application and the combination of 500 ppm Cu and 1.5% MP decreased the chlorophyll a content by 3% compared to the control (p<0.05), while the combination of 100 ppm Cu and 0.5% MP increased it by 2.5%. In tomato, 100 ppm Cu and 0.5% MP application decreased the chlorophyll b and total chlorophyll contents by 29% and 14%, respectively, while other applications caused an increase (p<0.05). There was no significant difference in the carotenoid contents compared to the control group. In kale, chlorophyll a, total chlorophyll and carotenoid contents did not significantly vary compared to the control group, while 500 ppm Cu application increased the amount of chlorophyll b by 15% (p<0.05). The results showed that tomato was more sensitive to Cu and MP applications than kale. The response in plants varied depending on whether Cu and MP were applied individually or combined.