Throughout this summer, I had the opportunity to study the effect of polyethylene microplastics (PE-MP) on the morphology, nutrient content, and hormonal regulation of Lactuca sativa (Romaine lettuce). There were three treatments in this study: the control (no MP), PE 500 (500μm sized PE-MP), and PE 50 (50μm sized PE-MP), with three replicates of each. The microplastics were mixed into the soil at a ratio of 1:100 (m:m). The lettuce seeds were planted, culled, and allowed to mature over 48 days. After lyophilizing the samples, various tests were run to measure markers of oxidative stress. These tests include salicylic acid analysis via HPLC, single element analysis (nutrients and heavy metals) via ICP, chlorophyll content via absorbance reading, and measuring physical characteristics of the plants. In general, the presence of PE 500 in the soil seemed to affect the lettuce most. Results showed that PE 500 led to a decrease in average fresh weight, a decrease in average total chlorophyll content, a decrease in total water mass, and increases in salicylic acid, cadmium, and calcium content.
