Effect Of Heavy Metal On The Photosynthesis And Quality Of Water Spinach And Radish Under Simulated Acid Rain

With pot experiments, the effects of heavy metal Pb (II), Cd (II) and Cr (VI) on the photosynthesis, nutritional quality and food safety of the water spinach (Ipomoea aquatica Forsk.) and radish (Raphanus sativus L. var. radculus Pers.) under simulated acid rain of various acidities were studied. The results showed that, with the increasing acidity of the rain, effects of different heavy metal treatment on the photosynthesis and quality displayed as: AR+Cd>AR+Pb+Cd> AR+Pb> AR+Pb+Cr> AR+Cr. In which, the influence of AR+Pb, AR+Pb+Cd and AR+Pb+Cr treatment enhance more remarkably with increasing acidity. When pH<4.5, the harm of AR+Pb+Cd and AR+Pb+Cr treatment was notably more serious than any other treatment and caused severe damage to the vegetables' physiology and quality. Analysis on the data of photosynthesis showed that, under co-pollution treatment, three parameters of decreased to different level, which showed the sensibility variation between parameters. Changes of the chlorophyll fluorescence mainly rest with the contents of chlorophyll-a. Analysis on the nutritional quality showed that, the content of soluble protein in two kinds of vegetables was much less than the control group, while the content of dissociated amino acid was increased under different treatment. Content of the soluble protein and the dissociated amino acid would be sharply reduced when pH<4.5. Additionally, when the content of soluble sugar raise with increasing acidity of the simulated acid rain, the content of reducible sugar was reduced remarkably, which was identified as a stimulus-controlled response? Research on the nitric nitrogen showed that, AR+Pb and AR+Pb+Cr treatment would notably promote nitric nitrogen accumulation in water spinach. Meanwhile, effects of different heavy metal treatment on the nitric nitrogen accumulation in radish displayed as: AR+Pb>AR+Pb+Cd>AR+Cd, and the effect would be enhanced with the increasing acidity. Pb rather than Cr is more likely to be accumulated by the water spinach, and the rate of heavy metal accumulation would speed up with the increasing acidity. The quantity of Cd enrichment in radish was much higher than the Pb, which would enhance with the increasing acidity of acid rain. AR+Pb+Cd treatment was most likely to cause heavy metal enrichment in radish. Finally, thewater spinach was more sensitive to the co-pollution while the radish was moretolerable to the acid rain effect with low acidity.