| Engineering nanomaterials have special physical and chemical properties,such as small size effect,surface and interface effect,and macroscopic quantum tunneling effect and so on,which have a wide range of applications and huge market potential.Multi-walled carbon nanotubes?MWCNTs?and nano-TiO2 are widely used in life science because of their complex structure,special properties,catalytic performance and oxidation resistance.In this study,L.perenne,Medicago sativa and Magnolia multiflora were used to study the effects of different concentrations of MWCNTs(0 mg·L-1?50 mg·L-1?100 mg·L-1?200 mg·L-1?500 mg·L-1)and nano-TiO2(0 mg·L-1?100 mg·L-1?500 mg·L-1?1000 mg·L-1?2500 mg·L-1)on seed germination and seedling growth.This study try to reveal the biological effect of engineering nanomaterials on plant growth and its mechanism.The experimental results are as follows:?1?Effects of MWCNTs on germination of plant seedsMWCNTs did not significantly promote the germination of L.perenne seeds,However,the germination rate,germination potential and germination index of L.perenne were higher than those of the control.At the concentration of 200 mg·L-1,the germination power and germination index of Medicago sativa seeds were significantly increased.At this treatment concentration,The germination rate,germination potential and germination index of Medicago sativa were significantly higher than those of the control,which indicated that the germination rate of herbage is very high,so the effect of MWCNTs on the germination rate of herbage is not obvious,but it can significantly shorten the germination time.Combined with the experimental data,it was found that the treatment of MWCNTs with concentration of 200 mg·L-1 had the most obvious effect on the germination of plant seeds.?2?Effects of MWCNTs on morphological indexes and biomass of plant seedlingsThe morphological indexes and biomass of L.perenne,Medicago sativa and Magnolia multiflora seedlings treated with MWCNTs were higher than those of the control,and the promotion effect of L.perenne,and Medicago sativa was more significant under the treatment of MWCNTs of lower concentration(50 mg·L-1,100 mg·L-1).When the concentration of MWNTs was 200 mg·L-1,the leaf length,stem length,stem diameter,leaf thickness and fresh weight of the seedlings were significantly higher than those of the control.The results showed that MWCNTs could significantly promote the growth and development of all plants in the experimental range,but leaf length,stem length,fresh weight and other indicators were more sensitive to the change of concentration,and the optimal concentration of different plants was also different.?3?Effects of MWNTs on physiological and biochemical indexes of plantsThe soluble protein of L.perenne,Medicago sativa and Magnolia multiflora seedlings treated with MWCNTs was higher than that of the control,which indicated that MWCNTs could stimulate the protein synthesis of seedlings,improve their stress resistance and ensure the normal growth and development of plants.The chlorophyll content of the seedlings treated with MWCNTs was higher than that of the control group.In addition,there is a significant negative correlation between the change trend of MDA content and enzyme activity of antioxidant system,which shows that the treatment of low concentration of MWCNTs can activate the activity of antioxidant enzymes in plant tissues,reduce the damage of cell membrane,and promote the growth and development of plants,but with the increase of treatment concentration,the excess of active oxygen in plants exceeds their own metabolic threshold,Therefore,the treatment of low concentration MWCNTs has the best effect on plant growth and development.?4?The effect of nano-TiO2 on the germination of plant seedsNano-TiO2 did not significantly promote or inhibit the germination of L.perenne seeds,but when the concentration was 1000 mg·L-1,it significantly increased the germination potential and germination index of Medicago sativa,and accelerated the germination rate of seeds.The results showed that nano-TiO2 had different effects on the germination of herbaceous seeds.There was no significant difference in the germination of Magnolia multiflora seeds treated with nano-TiO2 compared with the control,but the germination of Magnolia multiflora seeds was inhibited to some extent by the treatment of nano-TiO2.?5?Effects of nano-TiO2 on morphological indexes and biomass of plant seedlingsThe growth of L.perenne seedlings was promoted to some extent by the concentration of nano-TiO2,and the most significant effect was at the concentration of 2500mg·L-1.The concentration of 500 mg·L-1 nano-TiO2 had a significant promoting effect on the growth of Medicago sativa seedlings,but with the increase of the concentration of nano-TiO2,the promoting effect decreased slowly.The results showed that the growth and development of Medicago sativa seedlings could be inhibited by high concentration of nano-TiO2.Nano-TiO2 had a significant inhibitory effect on the growth of Magnolia multiflora seedlings.With the increase of the treatment concentration,the inhibitory effect was more and more obvious.?6?Effects of nano-TiO2 on physiological and biochemical indexes of plantsThe content of soluble protein and chlorophyll and the activity of POD and SOD enzyme in L.perenne and Medicago sativa seedlings increased with the concentration of nano-TiO2,The content of MDA was negative correlated with the concentration of nano-TiO2.The results showed that with the increase of the concentration of nano-TiO2,the content of active oxygen in the tissues of L.perenne and Medicago sativa seedlings increased.In order to remove excessive active oxygen,the activity of POD,SOD and CAT enzyme increased to improve the antioxidant capacity of seedlings,and the content of MDA decreased with the increase of the concentration,which indicated that the activity of antioxidant enzyme decreased the damage of cell membrane of seedlings.However,the content of soluble protein and chlorophyll of Magnolia multiflora seedlings treated with nano-TiO2 was lower than that of the control.With the increase of the concentration,the change trend of the enzyme activity of the seedlings treated with nano-TiO2 was as follows: the activity of POD,SOD and CAT was higher than that of the control under the treatment of low concentration nano-TiO2(0-500 mg·L-1),but with the increase of the concentration,the activity of antioxidant enzyme began to decrease,When the concentration is 2500 mg·L-1,the enzyme activity is the lowest.The results showed that the synthesis of protein was destroyed and the cell membrane was seriously damaged under the stress of nano-TiO2,which inhibited the growth and development of seedlings. |
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