Zinc accumulation and its effects on physiological dynamics and calcium distribution in submerged Macrophyte, Potamogeton crispus L.

Potamogeton crispus L.exposed to elevated concentrations of zinc(up to 20 mg·L-1) for 7 d were analyzed with reference to the accumulation of metal and its influence on mineral nutrients,photosynthetic pigments,non-enzymatic antioxidants(GSH and AsA),adenosine triphosphate(ATP),protein content and calcium distribution.It was found that,with the rise of the Zn2+ concentration in culture medium,(1)The accumulation of Zn2+ was increased in a concentration dependent manner.(2)Zn2+ resulted in imbalance of nutrient elements,and promoted the adsorption of Fe2+ and prohibited those of P5+ and Na+ significantly.(3)Chlorophyll a,b and Car contents reached the highest point at 5,5,10 mg·L-1 and followed by a decline,respectively.Chlorophyll a/b showed a decreasing trend.(4)A significant reduction in AsA content was observed in Zn2+ treated P.crispus,in contrast,an minor increase was noted in level of GSH at 5 mg·L-1 dose.(5)Soluble protein and ATP contents were found to be decreased at all Zn2+ concentrations.(6)Electron microscope observation revealed that Ca2+ mainly distributed within intercellular space and vacuole,some calcium deposits could be randomly found in cytoplasmic matrix under normal conditions.When different dose of Zn2+ was added into the culture solution,the calcium level in these compartments lowered while that in cytoplasm increased remarkably,especially bigger particles of calcium deposits appeared at the inner aspect of plasmalemma.In general,AsA was most sensitive to Zn2+ stress and the threshold of toxicity ranged from 5～10 mg·L-1.