Effect Of Nitrogen On The Yield And Baicalin Content Of Scutellaria Baicalensis Georgi

Scutellaria baicalensis Georgi.is a perennial herb belonged to the Labiaceae family,and its dried root(Radix Scutellariae)is one of the most commonly used Chinese medicinal materials.Baicalin is the most important active ingredient in Radix Scutellariae and its content is regarded as one of the important indexes in the evaluation of the Radix Scutellariae quality.At present,the planting area of S.baicalensis is expanding rapidly,but the decline in its yield and quality is becoming increasingly prominent and has become a major bottleneck,restricting the sustainable development of S.baicalensis industry.Aimed to provide theoretical evidence for nitrogen management and quality promotion of S.baicalensis,the effects of nitrogen on growth of S.baicalensis was investigated,the growth,dry matter accumulation,nitrogen uptake and quality buildup pattern of S.baicalensis in the authentic production area were elucidated,and the the relationship between the nitrate-nitrogen content in stem base and the yield of S.baicalensis was preliminary simulated in this study.The results of the experiments are as follows:(1)The effects of nitrogen application rate on the growth,dry matter accumulation,nitrogen accumulation and baicalin content of S.baicalensis in field trials were determined.The results showed that the growth-promoting effect of nitrogen on S.baicalensis did not increase with the increase of nitrogen application rate.The highest growth index,dry matter weight,nitrogen accumulation and baicalin content in roots of S.baicalensis were recorded at the nitrogen application rate of 120 kg/hm~2,which were significantly higher than those of 0-nitrogen and treatments of higher nitrogen application rates.At the same time,it was found that the taproots of S.baicalensis were stubby in the treatments of high nitrogen application rates,indicating that excessive nitrogen fertilizer caused inhibited the growth of S.baicalensis roots.(2)The effects of nitrogen application rate on the yield and economic efficiency of S.baicalensis production in the field trials were determined.The results showed that the yield and economic efficiency of S.baicalensis cultivation increased firstly and then decreased with the increase of nitrogen application rate.In treatments of high nitrogen application rates the yield and economic efficiency of S.baicalensis were reduced.The yield and economic efficiency of one-year and two-year S.baicalensis reached the maximum when the nitrogen application rate was 120 kg/hm~2,which were significantly higher than those of other treatments.The yields of one-year and two-year S.scutellaria dry roots were 1684.25 kg/hm~2and 3565.69 kg/hm~2respectively,which was increased by 18.74%and 14.80%as compared with those of the control,and by 24.19%and 26.61%as compared with those of the high nitrogen treatment,respectively.The economic efficiency was 43.11 thousand yuan/hm~2and 92.03 thousand yuan/hm~2respectively for one-year and two-year S.scutellaria production,which was increased by 17.15%and14.07%as compared with that of the control,and increased by 26.87%and27.93%as compared with that of the high nitrogen treatment.The dry root yield and economic efficiency of the two-year S.baicalensis cultivation in the high-nitrogen treatment were low.(3)The optimum range of nitrate concentration was 6.60 g/kg～6.63g/kg and 7.69 g/kg～7.73 g/kg in the mature stem base of one-year and two-year S.baicalensis respectively,which was correlated with the relatively high yield of S.baicalensis when harvesting.(4)The effects of different nitrogen forms on the growth of S.baicalensis under hydroponic conditions were determined.The results showed that the optimal concentration of nitrate nitrogen in hydroponic nutrient solution was 9 mmol/L,and S.baicalensis exhibited greater root length,root thickness and dry matter at this concentration.When the concentration was above 9 mmol/L,the promotion effect on root length,root diameter and dry matter weight of S.baicalensis was significantly decreased.The optimal concentration of ammonium nitrogen in hydroponic nutrient solution was 3 mmol/L,and S.baicalensis showed greater root length,root thickness and dry matter at this concentration.When ammonium nitrogen was above 3 mmol/L,the growth-promoting effect was abated significantly.S.baicalensis suffered the poisoning by ammonia that rendered as root rot and died when the ammonium nitrogen concentration was above 6 mmol/L.(5)A hydroponic experiment on the effects of various ratios of different nitrogen forms(nitrate nitrogen:ammonium nitrogen)on the growth and development of S.baicalensis was conducted.The results showed that a nitrogen concentration of 10 mmol/L and a nitrate nitrogen:ammonium nitrogen ratio of 10:0 promoted the growth of S.baicalensis,manifested as largest plant height,root length,root thickness,dry matter accumulation and highest content of baicalin in the root as compared with other treatments,and the differences reached significant levels.