Calcium Nutrition Regulation Characteristics And Application Effects Of Panax Quinquefolium L.

Calcium（Ca）is the second abundant mineral element in American ginseng（Panax quinquefolium L.）.Rational application of calcium fertilizer is key for the healthy growth and stress resistance of American ginseng.However,information about the calcium nutritional characteristics of American ginseng remains limited at home and abroad.Firstly,the hydroponic cultured 1-year-old American ginseng was used to determine the physiological effects of different calcium concentration([Ca²⁺])on it and the suitable[Ca²⁺]for its growth.Then,according to the characteristics of calcium could improve the minimum saturating irradiance of American ginseng,the changes of transcriptome and metabolome of American ginseng with calcium deficiency and high calcium under high temperature and strong light were studied,through the correlation analysis of transcriptome and metabolome,the mechanism of calcium improving the tolerance of American ginseng to high temperature and strong light was revealed.Furthermore,the soil cultured 2-year-old American ginseng was used to select the suitable types and application amount of calcium fertilizer for field use.The results of hydroponic culture showed that the biomass,stem height,and leaf area of American ginseng increased first and then decreased with[Ca²⁺]and peaked at[Ca²⁺]of 640.68mg/L,the stem diameter increased with[Ca²⁺].The contents of total chlorophyll and chlorophyll a increased first and then decreased with[Ca²⁺],reached the maximum at[Ca²⁺]of 160.17 mg/L and320.34 mg/L respectively,the content of chlorophyll b decreased with[Ca²⁺],and the ratio of chlorophyll a/b increased with[Ca²⁺].Fv/Fm increased first and then decreased with[Ca²⁺]and reached the maximum at[Ca²⁺]of 640.68 mg/L,Y（NPQ）increased with[Ca²⁺],Y（NO）decreased first and then increased with[Ca²⁺]and decreased to the lowest at[Ca²⁺]of 320.34 mg/L,Y（Ⅱ）,Ek,and Pn increased first and then decreased with[Ca²⁺]and reached their maximum at[Ca²⁺]of320.34 mg/L.SOD activity increased first and then decreased with[Ca²⁺]and reached the maximum at[Ca²⁺]of 640.68 mg/L,CAT,POD,and DHA activity increased first and then decreased with[Ca²⁺]and reached their maximum at[Ca²⁺]of 320.34 mg/L.The content of MDA and Pro decreased first and then increased with[Ca²⁺],the content of MDA decreased to the lowest at[Ca²⁺]of 160.17mg/L and 320.34 mg/L,the content of Pro decreased to the lowest at[Ca²⁺]of 160.17 mg/L.The suitable[Ca²⁺]for optimum growth of American ginseng was 320.34 mg/L.Transcriptome and metabolome analysis disclosed that American ginseng with calcium deficiency and high calcium initiated two different response mechanisms under high temperature and strong light.They had no common core difference genes,therefore,their core metabolites had corresponding differences,however,they also had common core metabolites:L-glutamate,L-cysteine and spermidine,and these amino acids decreased with calcium deficiency and increased with high calcium of American ginseng.The correlation analysis showed that the core differential genes and core metabolites of calcium deficiency American ginseng enriched inβ-Alanine metabolic pathway（ko:00410）,arginine and proline metabolic pathway（ko:00330）,glycine and serine and threonine metabolic pathway（ko:00260）;In high calcium American ginseng,the core differential genes and core metabolites enriched in Glutamate metabolic pathway（ko:00480）,compared with suitable calcium American ginseng,the gene（Pg＿S3572.10）related with glutathione metabolism in high calcium American ginseng significantly up-regulated by 1.29 times.The calcium content of roots,stems,and leaves of hydroponic American ginseng increased with[Ca²⁺],the order of calcium content was always stem>leaf>root.The[Ca²⁺]had a strong effect on the absorption of other elements,the magnesium content of American ginseng leaf peaked at[Ca²⁺]of 320.34 mg/L,where the content of aluminum and manganese content in roots was lowest,and the total saponin content was high.Calcium fertilizer screening test shown that calcium hydroxide and calcium sulfate were suitable for soil application,and the appropriate amount of calcium were 470.78 mg/kg.Calcium hydroxide could increase the soil p H and was conducive to the effective supply of other elements in soil and the accumulation of Rg₁ in root.Calcium sulfate could reduce the soil p H and the survival rate of American ginseng significantly,but it was conducive to the stability of photosynthetic mechanism and the accumulation of total saponins,Re and Rb₁ in the root.