The impact of drought stress on the physiological biochemical indexes and metabolites in Panax notoginseng.

Panax notoginseng is a traditional Chinese medicinal rich in saponins, polysaccharides and flavonoids, which have significant therapeutic effects on cardiovascular and cerebrovascular diseases. Climate change has led to an increase in global water and drought disasters, significantly impacting the growth of P. notoginseng plant and the synthesis of its active ingredients. Therefore, we focused on investigating the effects of drought stress on the biochemical indexes, accumulation of effective components and product of metabolism in P. notoginseng. Results indicated that P. notoginseng can survive in PEG 6000 (PEG) concentration ranging from 2.5% PEG to 7.5% PEG, however, its growth, physiological indicators, effective components content, and metabolize substances were significantly affected by PEG. When P. notoginseng was treated for 7 days by 7.5% PEG, which the contents of Pro in leaves and roots were 0.62 mg/g and 0.53 mg/g; POD were 461.08 U/g and 210.76 U/g; APX were 120.37 U/g and 54.46 U/g; MDA were 27.09 μmol/g and 22.66 μmol/g. It was treated by 5.0% PEG for 7 days, the content of saponins (R1, Rg1, Re, Rb1, and Rd) were 0.63%, 3.34%, 0.47%, 3.32% and 0.68%. It was treated by 7.5% PEG for 7 days, the contents of chlorophyll a, chlorophyll b, and total chlorophyll were 4.16 mg/g, 2.43 mg/g and 6.59 mg/g. Using LC-MS technology, we obtained 11,603 differential metabolites, among which 481 were upregulated and 1065 were downregulated. Cluster and KEGG enrichment analysis indicate that the differential metabolites of amino acids, glycerides, fatty acids, nucleotides, organic acids, and lipids were significantly up-expressed expression, and it were significantly enriched in metabolic pathways such as glycerol phospholipid metabolism, α-linolenic acid metabolism, carotenoid biosynthesis.