Study On Correlation Between Content And Accumulation Of Glycoside And Titanium Absorption In Stevia Leaves

The crop root nutrient ion absorption kinetics is of great significance in plant nutrition,it can reflect the different plants of ion absorption and nutritional conditions of adaptation level.It has been widely used in wheat,rice,corn and other crops on nutrient absorption,but there are few reports of studies on titanium absorption kinetics in Stevia.Stevioside has a high sweetness(200 to 300 higher than sucrose),and low calorie(only one three-hundredths to sucrose)with good heat resistance and safety characteristics.Stevioside not only does no harm to human body,but also has medicinal values such as in lowering blood pressure,physical strength and treatment of diabetes,making it a new kind of sugar source that can be used as a substitute for sucrose.Titanium is widely exist in nature.Although there is no definite evidence to prove that titanium is the essential nutrient for plant growth.It was found that titanium could promote the absorption and transport of nutrients,improve the content of chlorophyll in leaves,promote the enzyme activity,improve product quality etc.Through the preliminary study found that,Stevia is relative to the enrichment of titanium,it is several times or even several times than the other Chinese herbal medicines.What is the absorption method of such a high content of titanium by Stevia.Does the glycoside synthesis have an effect on content and accumulation of glycosides,and improve the quality of Stevia glycoside(the ratio of ST and RA).In this experiment,the absorption kinetics of titanium in different varieties of Stevia were studied using the method of water culture.The effects of respiratory inhibitor(malonic acid)on titanium absorption by Stevia and rice were compared.The application of titanium on the effects of stevioside content and accumulation were studied by indoor simulated foliar spray of titanium and soil application of titanium.The correlation analysis of the glycoside content and titanium absorption were studied by application different concentration of titanium.The main results are as follows:1?Absorption kinetics indicate that the titanium uptake increases with the increase of titanium contents and the uptake curve accord with the law of Michaelis-Menten.The maximum absorption velocity of Julong No.5 and Huichang No.4 were 0.11 milligram per plant per hour and 0.05 milligram per plant per hour,michaelis constant(Km)were 3.46 mg/L and 2.74 mg/L.The titanium uptake in Stevia was severely inhibited and the morphologies of its uptake kinetics curves were altered by respiratory inhibitor malonic acid,however,the uptake kinetics curves of rice were not affected by respiratory inhibitor.It is proved that the process in which Stevia absorbs titanium is an energy-dependently active absorption process.2?Both soil fertilization and foliar spray of titanium applications could significantly increase the stevioside content and accumulation in Stevia reaching to the maximum at the T3 treatment.Foliar spray of titanium make Julong No.5 and Huichang No.4 total content than ck increased 1.33 times and 1.39 times respectively,and the soil application is 1.22 times and 1.50 times respectively.The highest increase of stevioside total accumulation in Julong No.5 and Huichang No.4 were as high as 72.96% and 78.70% compared to ck by foliar spray of titanium,and soil application of titanium was only 42.05% and 50.84%.The results showed that the effect of foliar spray of titanium application was better than soil application.3?Correlation analysis showed that there are two polynomial model between foliar spray concentration or soil application rate and total accumulation of glycosides,and the correlation coefficient reached a significant level.The regression equations of Julong No.5 are as follows:y=-0.14234x~2+6.9098x+158.31(R~2=0.81623*)?y=-0.0306x~2+1.5481x+60.007(R~2=0.88738*);The regression equations of Huichang No.4 are as follows:y=-0.13396x~2+6.5122x+148.19(R~2=0.80711*)?y=-0.03246x~2+1.5987x+59.992(R~2=0.78705*).The results showed that the best concentration(or amount)of foliar application and soil application was 20~25mg/L(or mg/kg).4?With the concentration of foliar spray or soil application increased,there are two polynomial model between the titanium content and the glycosides content,the titanium accumulation and the glycoside accumulation in the leaves of Stevia,and the correlation coefficient reached a significant or extremely significant level.