Physiological Mechanism Of Bulb Development In Fritillaria Thunbergii Miq. In Response To Potassium Concentration

Objective To explore the relationship between the development of Fritillaria thunbergii Miq.bulbs and the level of potassium by measuring the dynamic changes of biomass and alkaloids in two varieties with distinct agronomic traits?Zhebei 1:Narrow-leaf type,Duozibei:Wide-leaf type?under different potassium levels;To determine the key substances and enzymes affected by potassium in carbon assimilation metabolismof Fritillaria thunbergii Miq.by determining substances and enzymes activities related to carbon assimilation metabolism in bulbs of two varieties at different potassium levels,and then reveal the physiological mechanism of bulbs development in response to potassium.Methods 1.A two-year repetitive field experiment?2017 and 2018?was conducted to research the effects of potassium application on bulb development of Fritillaria thunbergii Miq.at three potassium levels(0,80 and 160 kg K₂O hm^-2).2.The volume,fresh weight and biomass of old and new bulbs of Fritillaria thunbergii Miq.were measured by drainage,etc to compare the differences of development status of old and new bulbs of Fritillaria thunbergii Miq.under different potassium application.3.The content of peimine and peiminine in new bulbs was determined by high performance liquid chromatography to explore the effect of different potassium application on alkaloid content of Fritillaria thunbergii Miq.4.The content of soluble sugar,sucrose and starch in Fritillaria thunbergii Miq.bulbs was determined to reveal the effect of potassium application on the content of carbon metabolism substances in Fritillaria thunbergii Miq.bulbs.5.The activity of sucrose synthase,sucrose phosphate synthase,sucrase and amylase in Fritillaria thunbergii Miq.bulbs was determined to analyze the difference of key enzymes of carbon metabolism between two Fritillaria thunbergii Miq.cultivars under different potassium application.Results 1.Potassium application could significantly increase bulb volume,fresh weight and biomass of Fritillaria thunbergii Miq.The effect is most obvious when the potassium application is 80 kg K₂O hm^-2,while smaller at 160 kg K₂O hm^-2.2.Potassium application had a significant impact on the dynamic accumulation process of biomass and potassium accumulation in Fritillaria thunbergii Miq.The theoretical maximum,maximum cumulative rate and average cumulative rate of potassium accumulation increased significantly at 80 kg K₂O hm^-2.3.Appropriate potassium application can increase the content of effective components in new bulbs,but in terms of the dynamic trend,the concentration of potassium in bulbs is positively correlated with the content of peimine,negatively correlated with the content of peiminine,and has no significant correlation with the total amount of effective components Compared with Zhebei 1,the final active component content of Duozibei were more affected by potassium.4.Compared to 0 kg K₂O hm^-2,potassium application could increase the content of soluble sugar and sucrose in bulbs,promote the accumulation of starch and facilitate the expansion of Fritillaria thunbergii Miq.bulbs.The content of soluble sugar,sucrose and starch in bulbs increased significantly at 80 kg K₂O hm^-2.When K application was 160 kg K₂O hm^-2,the content of sugar in bulbs of Fritillaria thunbergii also increased,but slightly less than 80 kg K₂O hm^-2.while the arbohydrate accumulation in bulbs was decreased when potassium application was 160 kg K₂O hm^-2.5.Contrary to the activities of amylase(highest at 0 kg K₂O hm^-2),the activities of sucrose synthase,sucrose phosphate synthase and sucrase in Fritillaria thunbergii Miq.bulbs were the highest at 80 kg K₂O hm^-2,followed by 160 kg K₂O hm^-2,and the lowest at 0 kg K₂O hm^-2.The activities of enzymes and content of carbon assimilation substances in Duozibei were more affected by potassium than Zhebei 1.Conclusion Appropriate application of potassium could significantly increase the volume,fresh weight and biomass of Fritillaria thunbergii Miq.bulbs,and affect the dynamic process of potassium accumulation in Fritillaria thunbergii Miq.bulbs.Potassium application could increase the content of active ingredients in new bulbs,but the improvement effect of Zhebei 1 was not as good as that of Duozibei.The correlation between potassium concentration and active ingredients was complex in terms of dynamic changes,which needed further study.Suitable potassium application could significantly increase the contents of soluble sugar,sucrose and starch in Fritillaria thunbergii Miq.bulbs,increase the activities of sucrose synthase,sucrose phosphate synthase and sucrase,and inhibit the activities of amylase in bulbs.The sensitivity of two Fritillaria thunbergii Miq.varieties to potassium was different.Compared to Zhebei 1,Duozibei was more sensitive to potassium.