| Cadmium pollution is a major environmental problem faced by the current society.Excessive cadmium will cause irreversible harm to plants.Taking hydroponic soybean as the research object,the stress effects of different concentrations of cadmium chloride on soybean and the antagonistic effects of garlic by-products on cadmium stress were investigated from the indexes of seed germination,seedling growth,antioxidant enzyme system,root tip cell damage and cadmium content.The results showed that:1.Cadmium has a stress effect on hydroponic soybean,and the stress effect increases with the increase of concentration.(1)Cadmium inhibited the germination of hydroponic soybean seeds.The germination rate,germination potential,germination index and vigor index of soybean seedlings decreased with the increase of cadmium chloride concentration.Compared with the blank control group,the germination rate of soybean seeds in 200 mg/L and 300 mg/L cadmium chloride treatment groups decreased by 13.0%,the germination potential decreased by 20.0%,the germination index decreased by 37.3%and 38.3%,and the vigor index decreased by 83.1%and 85.0%respectively.(2)Cadmium inhibited the growth of hydroponic soybean seedlings.The root length,plant height,fresh weight,dry weight and tolerance index of soybean seedlings decreased with the increase of cadmium chloride concentration.Compared with the blank control group,the root length of soybean seeds in 200 mg/L and 300 mg/L cadmium chloride treatment groups decreased by 84.6%and 84.8%,plant height decreased by 75.2%and 77.6%,fresh weight decreased by 25.4%and 27.3%,dry weight decreased by 10.1%and 45.5%,and tolerance index decreased by 84.6%and 84.8%respectively.(3)After cadmium chloride treatment,superoxide dismutase(SOD)and peroxidase(CAT)could protect soybean under low concentration cadmium chloride stress and short culture time.On the third day,the SOD activity of 200 mg/L cadmium chloride treatment group increased by 250.0%compared with the blank control group.On the third day,the cat activity of 200 mg/L cadmium chloride treatment group was 34.8 u ·(g·min)-1.The content of malondialdehyde(MDA)in soybean seedlings increased with the increase of planting days and cadmium chloride concentration.On the third day,the MDA content of 300 mg/L cadmium chloride treatment group was 0.0142 μmol·g-1。2.Garlic by-product can improve the stress of cadmium on hydroponic soybean.(1)Garlic by-product can improve the stress effect of cadmium on Seed Germination of hydroponic soybean.After adding garlic by-products,the germination rate,germination potential,germination index and vigor index of soybean seedlings were higher than those of the positive control group.Compared with the positive control group,when the concentration of garlic by-product was 8 g/L and 10 g/L,the germination rate increased by 7.3%and 12.3%,the germination potential increased by 11.3%and 19.2%,the germination index increased by 23.2%and 31.9%,and the vigor index of soybean seeds increased by 65.2%and 110.5%respectively.(2)Garlic by-product can improve the stress effect of cadmium on the growth of hydroponic soybean seeds and seedlings.After adding garlic by-products,the plant height,root length,fresh weight,dry weight and tolerance index of soybean seedlings were higher than those of the positive control group.When the concentration of garlic by-product was 8g/L and 10g/L,the plant height was 3.94 and 4.69 cm,the root length was 0.97 and 0.99 cm,the fresh weight was 6.94 and 7.17 g,the dry weight was 1.80 and 1.86 g,and the tolerance index was 256.82 and 272.73,which were significantly higher than those in the positive control group.(3)After adding garlic by-products,the chlorophyll content was higher than that of the positive control group,the cell morphology of soybean leaves was improved,the palisade tissue was more dense and orderly,the number of xylem cells increased,and the content of sponge cells increased,indicating that the degree of cadmium stress on plants decreased.3.Garlic by-product can antagonize the stress of cadmium on hydroponic soybean.(1)The cadmium content of soybean seedlings in garlic by-product treatment group was lower than that in positive control group.Cadmium was mainly concentrated in plant roots,and the cadmium content in stems and leaves was significantly lower than that in positive control group.The cadmium content in stems of soybean seedlings in 6 g/L,8 g/L and 10 g/L garlic by-product treatment group decreased by 68.9%,70.9%and 87.7%respectively,and the cadmium content in leaves of soybean seedlings decreased by 35.0%,55.0%respectively 80.0%。(2)Antioxidant enzyme system and malondialdehyde are involved in the antagonistic process of garlic by-products against cadmium stress.After adding different concentrations of garlic by-products,the content of MDA decreased significantly compared with the positive control.On the 10th day,when the concentration of garlic by-products was 10 g/L,it decreased by 85.4%compared with the positive control.(3)Garlic by-products can improve the nuclear damage of root tip of Soybean Seedlings under cadmium stress.After garlic by-product treatment,the mitotic index of soybean root tip cells increased and the micronucleus rate decreased.Compared with the positive control group,the mitotic index of 6 g/L,8 g/L and 10 g/L garlic by-products treatment group increased by 76.4%,59.0%and 37.6%respectively,and the micronucleus rate decreased significantly by 58.1%,62.2%and 92.2%respectively.(4)Garlic by-products can improve DNA damage in root tip cells of Soybean Seedlings under cadmium stress.After adding garlic by-products,olive tail momentum(OTM),DNA tail content,comet tail length and tail distance were lower than those in the positive control group.Compared with the positive control group,there was significant difference in 8 g/L and 10 g/L garlic by-product treatment group,and the OTM decreased by 85.7%and 88.9%respectively;The DNA content of tail decreased by 77.9%and 89.0%respectively;The length of comet tail decreased by 69.4%and 75.7%respectively;The tail distance decreased by 91.1%and 94.5%respectively.Conclusion:cadmium has a stress effect on hydroponic soybean.Garlic by-products of appropriate concentration can improve the stress effect of cadmium on hydroponic soybean.The improvement mechanism may be related to reducing the absorption of cadmium by plants and reducing the damage of genetic material in root tip cells.Antioxidant enzyme system is also involved in the process of anti stress. |
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