Drought stress improves the composition of secondary metabolites in safflower flower at the expense of reduction in seed yield and oil content

摘要

<br/>Abiotic stresses like drought may modulate the synthesis of plants' secondary metabolites, with various pharmacological effects. In this study, the influence of water deficit was determined on safflower (Carthamus tinctorius L.) seed yield and oil content as well as antioxidant activity and phenolic and flavonoid compounds of both seed and flower for their industrial application. Eight safflower genotypes were planted in the field in two separate experiments under normal and water deficit conditions in a randomized complete block design. Agronomic traits of the genotypes were measured and their polyphenolic compounds were evaluated using liquid chromatography analysis. Results indicated that averaged over all genotypes and under normal irrigation conditions, seed yield and antioxidant capacity of seed extracts were 74% higher and 2.32 times of those under drought stress conditions, respectively. In contrast, under water stress, flower extracts had 2-fold antioxidant capacity at the expense of a significant decrease in seed yield, seed oil content, and antioxidant capacity of the seeds. The most abundant polyphenolic components in flowers of most genotypes which accumulated due to water stress were vanillic and caffeic acids. While in seeds, rutin and quercetin were more accumulated under normal irrigation regime. Interestingly, three components of apigenin, luteolin, and ferulic acid were not detected in flower extract of any genotypes in both irrigation regimes. The contrasting status of seeds vs. flowers under two environmental conditions were depicted by multivariate data analysis. Based on the principal component analysis, under normal irrigation regime, the higher antioxidant activity of the seeds (seed preferability) was correlated with total content and compounds of flavonoids. In contrast, in water deficit condition, the higher antioxidant activity of the flowers (flower preferability) was correlated with total phenolic content and vanillic, caffeic, and p-coumaric acids. Finally, one breeding line may be introduced with high seed yield and quality under both irrigation regimes, which its higher drought tolerance is possibly due to the induced synthesis of caffeic acid and quercetin.

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