Effects Of Ultraviolet Stress On Accumulation Of Main Medicinal Constituents Of Glechoma Longituba

Objective:This paper takes the medicinal plant G.longituba,as the research material,to explore the effects of UV stress on growth,oxidative stress and accumulation of main medicinal components of G.longituba,and to obtain high quality and high yield G.longituba by directional cultivation.Methods:1.Based on half of the culture medium of Japanese garden test,U₇（7⁴）uniform design experiment was adopted,with the flavonone content as the dependent variable y,Ca（NO₃）₂·4H₂O（mg/L）（A）,KNO₃（mg/L）（B）,（NH₄）₃PO₄·3H₂O（mg/L）（C）and Mg SO₄·7H₂O（mg/L）（D）were used as independent variables.A linear equation model was established and a regression equation was obtained to optimize the proportion of mass elements in the culture medium.2.Ultraviolet irradiation with radiation intensity of 0.15 m W/cm²,0.30 m W/cm²and 0.45 m W/cm²were used to stress the hydroponic seedlings of G.longituba for 2 h,4 h,6 h,8 h and 10 h.And ultraviolet irradiation with radiation intensity of 0.30 m W/cm²were used to stress the hydroponic seedlings of G.longituba for 1 h and 2 h respectively.The growth of G.longituba was observed and the water content and the protein content were measured.3.The content of malondialdehyde（MDA）,Proline（Pro）,H₂O₂and the activity of superoxide dismutase（SOD）,Peroxidase（POD）,ascorbate peroxida（APX）and catalase（CAT）were detected after UV stress.4.The content of polysaccharide was determined,the content of ursolic acid,oleanolic acid and chlorogenic acid was determined by high performance liquid chromatography（HPLC）,and the content of total flavonoids was determined.Results:1.The regression equation of total flavonoids content and mass elements in Pennisetum is:Y=0.335+0.009D-3.002×10^-5（C×D）-4.564×10^-6（B×D）+8.428×10^-6（B×C）,so the optimized formula of mass elements in culture medium is:When Ca（NO₃）₂·4H₂O was 189.00 mg/L,KNO₃889.9 mg/L,（NH₄）₃PO₄·3H₂O was30.6 mg/L,Mg SO₄·7H₂O was 542.3 mg/L,the content of flavonoids was the highest,reaching 3.47%.2.UV stress affected the growth of G.longituba.Whether under continuous stress or under normal culture for a short time,leaf burns and water loss of pennisetum officinalis were gradually serious,and protein content was significantly increased.3.After UV stress,the oxidative stress level of G.longituba changed dramatically.Under uv stress,the MDA level of G.longituba increased first and then decreased,and the MDA level did not recover to the pre-stress level after 1-2 h of normal culture.Pro content increased significantly after stress.H₂O₂content increased first and then decreased;CAT and APX increased and decreased regularly with the change of H₂O₂content.Under UV stress,SOD activity fluctuated greatly,but was basically higher than CK treatment.When POD was exposed to UV stress,its activity began to deactivate.After normal culture,POD activity recovered rapidly and remained at a high level.4.The highest content of polysaccharide was obtained under UV radiation of 0.30 m W/cm²for 6 h,which was 2.00 times of that before UV stress.Ursolic acid content reached 1.22 mg/g DW at 0.30 m W/cm²uv stress for 1h.The content of oleanolic acid was the highest under 0.15 m W/cm²UV stress for 2 h or 0.30 m W/cm²UV stress for 1 h,which was 55.95%higher than before.Under the UV stress of 0.45 m W/cm²for 2 h,the content of chlorogenic acid.chinensis was the highest,which increased by 108.80%compared with the control group.Under UV stress of 0.30 m W/cm²for 1 h,the content of total flavonoids was the highest,which increased by 1.12 times compared with the control group.Conclusion:UV stress can effectively increase the content of main medicinal components of G.longituba.by regulating the oxidative stress level of G.longituba,which is of great significance for the directional cultivation of G.longituba.