Bisulfite (HSO3(superscript -)) Hydroponics Induced Oxidative Stress and Its Effect on Nutrient Element Compositions in Rice Seedlings

Rice seedlings (Oryza sativa, cv. Liangyou peiju) were kept under hydroponic conditions in Hoagland solution containing sodium bisulfite (1, 2, 4 and 5 mM) for 3 days. To investigate the status of oxidative stress in tissue and cell levels in vivo, changes in the uptake/balance of main nutrient elements induced by bisulfite, as well as changes in the generation site and amount of active oxygen species O(superscript -• subscript 2) and H2O2 , the contents of photosynthetic pigments and the total contents of S, P, N, C, K, Na, Ca, Mg were assayed. In shoots, bisulfite treatment resulted in a significant accumulation of sulfur and a less pronounced accumulation of P, K, Na, Ca and Mg, but a reduction in C, N and chlorophyll contents. Each element to sulfur ratio was decreased as a result of increased sulfur content, and the ratio was negatively correlated to the treated bisulfite concentration. In contrast, most of the test elements in roots decreased upon bisulfite treatment, leading to an increase in the shoot/root ratio of nutrient elements. Histochemical and cytochemical localization of the two reactive oxygen species showed that generations of O(superscript -• subscript 2) and H2O2 were significantly enhanced by bisulfite in rice leaves. In epidermis tissue, H2O2 was predominantly present in guard and subsidiary stomata cells and some epidermal cells, while O(superscript -• subscript 2) was found in most epidermal cells. In mesophyll cells, H2O2 occurred firstly on the plasmalemma and cell wall conjunction point, and then expanded to cell wall and even to thylakoid in chloroplasts as bisulfite concentration increased.