| Pot experiments were carried out to determine the effects of the previous soybean crops treated with exogenous abscisic acid(ABA) on the subsequent maize crops. Soybean seeds were soaking or soybean leaves were sprayed at the initial flowering stage by ABA solutions of6concentrations, as0(the control),1,5,10,20and40μmol·L-1espectively, and antioxidant enzyme activities, carbon and nitrogen metabolism, nutrient contents as well as zinc, chromium contents of maize and soil avaliable nutrient contents and zinc, chromium contents were determined. The main findings were as follows:(1)Under zinc and chromium stress, the previous soybean treated with different ABA concentrations in two methods(spraying and soaking) could improve the subsequent maize crops’antioxidant enzyme activities in some extend. The spraying treatments improved superoxide dismutase(SOD) activities and catalase(CAT) activities of the maize roots better than the soaking treatments, while the soaking treatments increased catalase activities of the leaves and decreased the malondialdehyde(MDA) contents better than the spraying treatments. And both methods in defferent concentrations increased or decreased the peroxidase(POD) activities of the roots and leaves and MDA contents of the leaves. The maximum SOD activeties of the roots and the leaves were in the spraying treatments of40and40μmol·L-1ABA respectively, and the maximum POD activeties of the roots and the leaves were in the soaking treatments of10μmol·L-1and the spraying treatments of1μmol·L-1ABA respectively, the maximum CAT activeties of the roots and the leaves were in the spraying treatments of1μmol·L-1ABA and the soaking treatments of20μmol·L-1ABA respectively. The minimum MDA contents of the roots, leaves and stems were in the soaking treatments of10and40μmol·L-1ABA, the spraying treatments of1μmol·L-1ABA respectively.(2) Under zinc and chromium stress, the previous soybean treated with different ABA concentrations in two methods could improve the subsequent maize crops’ soluble sugar and soluble protein synthesis in some extend. The soaking treatments decreased the soluble sugar contents of the maize roots and increased the soluble sugar contents of the maize stems and leaves(except40μmol·L-1ABA increased the leaves soluble sugar), while the spraying treatments increased soluble sugar contens of the roots only with the concentration of10μmol·L-1ABA, of the stems with the concentration of5μmol·L-1ABA and40μmol·L-1ABA, and of the leaves with all concentrations except for1μmol·L-1ABA. The soluble protein contents increased or decreased in the soaking treatment and the spraying treatment with different concentrations, except the soaking treatment with1μmol·L-1ABA could enhance the soluble protein of the roots, stems and leaves simultaneously. The maximum soluble protein contents of the roots, stems and leaves were respectively in the spraying treatment of10μmol·L-1ABA, the soaking treatment of1μmol·L-1ABA, and the spraying treatment of1μmol·L-1ABA.(3) Under zinc and chromium stress, the previous soybean treated with different ABA concentrations in two methods could regulate nutrient uptakes of the subsequent maize crops in some extend. The spraying treatments of1and10μmol·L-1ABA and the soaking treatments of20,40μmol·L-1ABA could improve soil available nitrogen, available phosphorus and available potassic simultaneously; the nutrient uptaken by the maize and distributed in the roots, stems and leaves displayed different in the spraying treatments and the soaking treatments:all the treatments imporoved the roots nitrogen contents, and the nitrogen contents in leaves were higher than those in the roots and stems. The potassic contents distributed in the stems and leaves higher than those in the roots.(4) Under zinc and chromium stress, the previous soybean treated with different ABA concentrations in two methods could regulate zinc and chromium uptake by the subsequent maize crops in some extend. The soaking treatments decreased zinc contents in the roots, stems and leaves of the maize, except40μmol·L-1ABA inceased zinc content in the root, while the spraying treatments mainly reduced leaves zinc contents. As for the chromium accumulations, the soaking treatments enhanced the roots and decreased the stems and the leaves, except5μmol·L-1ABA decreased the roots and enhanced the stems and the leaves, while the chromium contents in the roots, stems and the leaves all decreased in the spraying treatments of1and20μmol·L-1ABA.(5) The previous soybean treated with20μmol·L-1ABA in the method of spraying had the optimal effect on improving the maize resistance, regulating nutrients uptake and decreasing zinc and chromium accumulations under zinc and chromium stres... |
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