The Morphological And Physiological Responses Of Leguminous And Gramineous Forage To Cobalt Level Of Soil

The study of the effects of Cobalt on animals and plants was started since the beginning of 20's last century, its effects in plant nourishment has not been studied untill 1950's, it has been proved that Cobalt is essential to the nitrogen fixation of blue algae, microorganisms and Leguminous plants, also, Cobalt is essential to animals and human beings. This study consists of two parts:First part:This part was done through pot experiment, after evaluating the 100 materials by the indexes of relative survival rate, relative plant height, relative biomass and relative plasmalemma permeability. we can get the conclusions below:⑴Of the 30 materials of alfalfa, highly Co-tolerant ones are Medicago sativa L. cv. Wudi, Medicago sativa L. cv. Hexi, Medicago sativa L. cv. Crown(from the USA), lowly Co-tolerant ones are Medicago sativa L. cv. Huaiyin, Medicago sativa L. cv. Jinnan, Medicago sativa L. cv. Shanbei. Compared in terms of type, the order is introduced variety>bred variety>local variety.⑵Of the 30 materials of clover, highly Co-tolerant ones are 86-339(Trifolium pratense, from Sweden), 81-87(Trifolium repens, from Danmark), 2000-71(Trifolium pratense, from Canada ), lowly Co-tolerant ones are 87-17(Trifolium pratens, from Holland),81-49(Trifolium pratens, from Australia),80-89(Trifolium pratens, from Australia)。⑶Of the 30 materials of tall fescue, highly Co-tolerant ones are 92-112(from Germany), 85-95 (from Holland), 93-25(from the USA), lowly Co-tolerant ones are 99-9(from the USA), 97-79 (from Holland), 93-23(from the USA).Second part:This part was done by Germination Test and Pot Experiment, after measuring growth and physiology indexes of five Legumes, Madicago sativa Linn, Trifolium repens Linn, Lespedeza bicolorTurcz, Lotus corniculatus Linn, Astragalus adsurgens Pall, we can get the conclusions below:⑴Low concentration Co treatment increased the germination energy, germination rate and germination index, while the high concentration Co treatment prevented the above three indexes. The effects of low concentration Co treatment on the length of radicle, germ were different within materials, however, the high concentration Co treatment showed definely inhibitory to both indexes, the change extent of germ length of the was smaller than that of radicle, else, the germ length to Co treatment was not as sensitive as the radicle length, more, Co treatment was not good to the cross growth of materials.⑵The survival rate of the materials fluctuated slightly under the low Co concentration treatment, while the plant height and biomass of them increased, of the high Co concentration, three indexes of materials all reduced, though there were differences in reduction extent. As the Co concentration became higher, the net photosynthetic rate and transpiration rate increased at first and then decreased, the effects of Co treatment on the two indexes showed the"Hormesis effect". The relative plasmalemma permeability and MDA content fluctuated slightly under the low Co concentration treatment, however, with the Co concentration getting higher, the value of the two indexes reduced significantly.The soluble sugar content decreased under low Co concentration treatment, but the difference was not significant to the control, with the Co concentration getting higher, the value of both indexes also increased significantly, when Co concentration reached a level the materials could not endure, the value of two index came about a nonreversible decrease. The activity of POD, CAT reduced under low concentration treatment, with the Co concentration becoming higher, the activity of them became higher too, when the concentration reached a level that the materials could not endure, the activity of two antioxidant enzyme came about a nonreversible decrease.