Diallyl phthalate-triggered oxidative stress in Spirodela polyrhiza L. Schleiden: physiological effects and role of antioxidant defence system

The present study was designed to investigate the manifestations of diallyl phthalate (DAP)-induced oxidative stress in Spirodela polyrhiza. Plants were exposed to varying concentrations of DAP, viz. 10, 20, 40, 80, 100, 200, 400 ppm for 7 days under in vitro conditions. Biochemical analysis after harvesting revealed various phytotoxic effects of DAP on S. polyrhiza which was quite evident from a significant decline in fresh weight and dry-to-fresh weight ratio with progressively increasing concentrations of DAP. Plants accumulated a significant amount of DAP (92.00 mg/kgfw) at 80 ppm concentration which led to alterations in photosynthetic pigments (chl a, chl b, total chlorophyll), increase in carotenoid and anthocyanin pigment, increase in lipid peroxidation, decrease in protein and carbohydrate content. Results also revealed significant effects of DAP on increased proline, phenols and electrolyte leakage. In response to this and to confer DAP tolerance in S. polyrhiza, activities of antioxidant enzymes (SOD, APX, CAT, POD and GR) elevated with proceeding concentrations. Moreover, toxicological implications in plants were confirmed by observing scanning electron micrographs and confocal micrographs of frond and root, respectively, implying oxidative damage faced by plant under DAP exposure. Considering all these results into account, it appeared that there are alarming consequences of DAP toxicity to S. polyrhiza and this plant exhibited better phthalate tolerance ability attributed to its efficient antioxidant machinery which may play a cardinal role in combating diallyl phthalate-mediated stress.