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Combined effects of light reduction and ammonia-nitrogen enrichment on submerged macrophyte Vallisneria natans
The decline of submerged plants resulting from low light and high ammonia nitrogen (ammonia-N) has become a serious problem worldwide. In this study, three levels of ammonia-N concentrations (0, 3, and 6 mg L-1) and four levels of light intensity (control, 15%, 2.5% and 0.75% underwater light) were designed to investigate the combined effects of low light and high ammonia-N stress on a submerged plant, Vallisneria natans. We examined the effects by measuring the relative growth rate (RGR), chlorophyll contents, superoxide dismutase activity (SOD), and peroxidase activity (POD) in response to the stressors. The results showed that the decline in RGR and increase in SOD and POD in high ammonia-N water were more significant than those in low light conditions, indicating that the stress imposed on submerged plants due to ammonia-N enrichment are stronger. Moreover, the combination of ammonia-N enrichment and low light had a greater impact on submerged plants. These findings suggest that low light restricts the growth of submerged plants and amplifies the effects of high ammonia-N to V. natans.
MF17146 Accepted 29 September 2017
© CSIRO 2017