Acute Drought Stress and Plant Age Effects on Alkamide and Phenolic Acid Content in Purple Coneflower Roots

Abstract

The effects of acute periods of drought stress on dry weight, and alkamide and phenolic acid content in purple coneflower [Echinacea purpurea (L.) Moench, Asteraceae] roots are described. Plants subjected to brief drought stress periods for two seasons during the initial flowering stage (D-F2) produced fall-harvested roots with significantly greater cichoric acid concentration (mg/g) than corresponding well-watered controls of the same age (C-2). Total alkamide, including the tetraenoic acid isomers, and chlorogenic acid concentrations from fall-harvested roots were largely unaffected by drought stress, regardless of when the stress occurred developmentally. The alkamide concentration in three-year roots was significantly less than that in two-year roots, with an average decrease of 50.5 %. Conversely, total phenolic acids increased an average of 67.1 % for all treatments from two to three years of age. Root dry weight increased significantly by an average of 70.0 % for all drought-stressed plants from two to three years of age, compared to an increase of 35.2 % for well-watered controls. The results suggest that controlled drought stress can stimulate increased root dry weight and root cichoric acid content, and that root age is the predominant factor determining overall phytochemical content variation.

Abbreviations

D-F1:Plants that received drought stress during the flowering period for one season (Season 1)

D-F2:Plants that received drought stress during the flowering period for two consecutive seasons (Season 1 and Season 2)

D-S1:Plants that received drought stress during the seed production period for one season (Season 1)

D-S2:Plants that received drought stress during the seed production period for two consecutive seasons (Season 1 and Season 2)

D-FS1:Plants that received drought stress during both flowering and seed production periods for one season (Season 1)

D-FS2:Plants that received drought stress during both flowering and seed production periods for two consecutive seasons (Season 1 and Season 2)

C-1:Control plants that received adequate water for one season (Season 1)

C-2:Control plants that received adequate water for two consecutive seasons (Season 1 and Season 2)

CCA:Cichoric acid (2,3-O-di-caffeoyl-tartaric acid)

CTA:Caftaric acid (2-O-caffeoyl-tartaric acid)

CGA:Chlorogenic acid (3-O-caffeoyl-quinic acid)

AMD:The sum of six alkamides (undeca-3E,4Z-dien-8,10-diynoic acid isobutylamide; undeca-2Z,4E-dien-8,10-diynoic acid isobutylamide; dodeca-2E,4Z-dien-8,10-diynoic acid isobutylamide; undeca-2E,4Z-dien-8,10-diynoic acid 2-methylbutylamide; dodeca-2E,4E,10E-trien-8-ynoic acid isobutylamide; dodeca-2E,4Z-dien-8,10-diynoic acid 2-methylbutylamide)

TET:The sum of two tetraenoic acid isomers (dodeca-2E,4E,8Z,10E-tetraenoic acid isobutylamide and dodeca-2E,4E,8Z,10Z-tetraenoic acid isobutylamide)

ψ_pd:Predawn water potential

Key words

Echinacea purpurea - Asteraceae - purple coneflower - water potential - alkamides - cichoric acid

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