Physiological Mechanism Of Leaf Carbon Metabolism Of Fritillaria Thunbergii Miq. In Response To Potassium Concentration

Objective In order to solve the problem of applying potassium fertilizer on Fritillaria thunbergii Miq.,the relationship between the physiological characteristics of Fritillaria thunbergii Miq.leaves affected by potassium and their carbon assimilation metabolism was clarified,and the key substances and enzymes affecting Carbon Assimilation Metabolism in Fritillaria thunbergii Miq.leaves and their mechanism were clarified.Methods The field experiment was conducted using varieties of Fritillaria thunbergii Miq.?Narrow leaf variety:zhebei 1;Wide leaf variety:duozibei?under three K levels(0,80 and160 kg K₂O hm^-2).The leaves of Fritillaria thunbergii Miq.were divided into upper,middle and lower layers.During the key growth stages of Fritillaria thunbergii Miq.,potassium concentration in leaves was measured,and its agronomic traits,chlorophyll content,photosynthetic performance and biomass were also measured.The relationship between yield and quality was analyzed under different potassium levels.The mechanism of potassium affecting source-sink balance and yield and quality of Fritillaria thunbergii Miq.was explored.The soluble sugar,starch and sucrose in Fritillaria thunbergii Miq.leaves were analyzed.The change range of sugar determined the key substances of carbon assimilates responding to potassium,analyzed the activities of enzymes related to carbon assimilation and metabolism in leaves,and clarified the physiological mechanism of physiological characteristics of Fritillaria thunbergii Miq.leaves responding to potassium concentration in plants.Results 1.With the development of growth period,leaf weight,SPAD and net photosynthetic rate of Fritillaria thunbergii Miq.increased first and then decreased,reaching the maximum at 67-69 days after emergence.The single leaf area and plant biomass of Fritillaria thunbergii Miq.increased with the development of growth period.Comparing different potassium application treatments,it was found that the agronomic traits and photosynthetic indexes of the two varieties reached the maximum at 80 kg K₂O hm^-2.The comparison among varieties showed that zhebei 1was better than duozibei.2.The concentration of potassium in Fritillaria thunbergii Miq.leaves increased with the increase of potassium application,and increased first and then decreased with the advance of growth period.Potassium concentration in upper leaves was significantly lower than that in middle and lower leaves at early growth stage.Compared with the control group(0 kg K₂O hm^-2),the final biomass and potassium accumuLation of 80 kg K₂O hm^-2and 160 kg K₂O hm^-2treatments increased significantly by 17.82%-21.70%.Compared with the two cultivars,the potassium accumuLation of leaves of duozibei was significantly higher than that of zhebei1,and the results of two years were the same.3.Comparing the proportion of potassium in Fritillaria thunbergii Miq.leaves,the proportion of potassium in lower leaves was the largest.Potassium accumulation in leaves of each layer under 80 kg K₂O hm^-2reached the maximum.Comparing the two varieties,it was found that the accumuLation ratio of potassium in the upper leaves of zhebei 1?29.73-38.06%?was significantly higher than that of duozibei?4.58-17.84%?.The accumulation of potassium in the leaves of Zhebei 1 was mainly distributed in the upper and middle leaves,while duozibei was mainly distributed in the lower leaves.4.With the advancing ofFritillaria thunbergii Miq.growth period,soluble sugar,starch and sucrose in Fritillaria thunbergii Miq.leaves increased and then decreased,and reached the maximum at 67-69 days after emergence.Compared with the control group(0 kg K₂O hm^-2),the soluble sugar content of 80 kg K₂O hm^-2and 160 kg K₂O hm^-2decreased by18.66-20.08%and 8.99-12.17%on average.Potassium application increased starch content in leaves,but there was no significant difference in starch content among different layers of leaves.The sucrose content of Fritillaria thunbergii Miq.treated with 80 kg K₂O hm^-22 at early stage was significantly higher than that of the other two groups at 69 days after emergence.However,after 69 days,the sucrose content in leaves decreased significantly,and the sucrose conversion rate reached the highest.5.The activity of amylase and SuSy increased under potassium application,and the activity was the best in 80 kg K₂O hm^-2treatment.The activity of sucrase in Zhebei 1 was higher than that in duozibei,but decreased under potassium application.The activity of SuSy was significantly higher than that of SPS.With the increase of potassium application,the activity of SPS and Rubisco inFritillaria thunbergii Miq.leaves increased,and that duozibei was stronger than that in zhebei 1.The activity of enzymes increased first and then decreased with the development of growth period,reaching the peak at 67-69 days after seedling emergence.6.Potassium concentration in Fritillaria thunbergii Miq.leaves was positively correlated with leaf area,leaf weight and biomass,while potassium concentration was positively correlated with sucrose,amylase,invertase,SPS enzyme and Rubisco enzyme.In zhebei 1,the potassium concentration in Fritillaria thunbergii Miq.leaves was positively correlated with starch.The soluble sugar and starch in Fritillaria thunbergii Miq.leaves were positively correlated with amylase,invertase,SPS and SuSy.Conclusion The effect of potassium on Fritillaria thunbergii Miq.leaves is to increase SPAD,net photosynthetic rate,leaf weight and leaf area by affecting its photosynthetic characteristics.Under the optimum potassium concentration,the photosynthesis of Fritillaria thunbergii Miq.leaves is strong at the early stage of growth.Soluble sugar,sucrose and starch accumuLate as photosynthates in leaves,but at the later stage,the leaves act as source organs of amylase,SPS and SuSy.Increased activity decomposes carbon metabolites into sucrose and transports them to sink organs such as bulbs.Appropriate potassium can improve the sucrose conversion rate of potassium,which is conducive to the accumulation of plant biomass.Comparing the two varieties,it was found that Zhebei 1 had better agronomic traits and was more sensitive to potassium.