The effect of seed source, light during germination, and cold-moist stratification on seed germination in three species of Echinacea for organic production

Abstract

Organic production of one of the most popular botanical supplements, Echinacea, continues to expand in the U.S. Echinacea seeds typically show a high degree of dormancy that can be broken by ethephon or gibberelic acid (GA), but these methods are currently disallowed in organic production. In order to determine the efficacy of non-chemical seed treatments, we evaluated the effect of varying seed source and supplying light, with and without cold-moist stratification, on seed germination of the three most important medicinal species of Echinacea, E. angustifolia DC, E. purpurea (L) Moench, and E. pallida (Nutt.) Nutt. Treatments included cold-moist stratification under 24 h light, 24 h dark, and 16/8 h light/dark to break seed dormancy. We found that germination was greater in the E. purpurea and E. pallida seeds from a commercial organic seed source compared to a public germplasm source. When seeds were not cold-moist stratified, 16-24 h light increased germination in E. angustifolia only. Echinacea angustifolia, E. purpurea, and E. pallida seeds that were cold-moist stratified under 16-24 h of light for 4 wk had a significantly greater percentage and rate of germination compared to seeds germinated in the dark. Therefore, cold-moist stratification under light conditions is recommended as a method to break seed dormancy and increase germination rates in organic production of Echinacea.

Figure 1

Effect of light during germination of non-stratified E. angustifolia, E. pallida, and E. purpurea seeds. Germinated seeds were counted 10 days after initiation of the experiment. Treatments in were 24 h of dark, 24 h of light, and 16/8 h of light/dark at a constant temperature of 25 °C. Bars represent the standard error of the mean. Bars within each group with different letters are significantly different at P = 0.05 according to Fisher's test.

Figure 2

Effect of light during cold-moist stratification on Echinacea (combined E. angustifolia, E. pallida, and E. purpurea) seed germination. The cold-moist stratification treatment consisted of 4 wk at 4 °C under either 24 h of light, 24 h of dark, or 16/8 h of light/dark. Control treatment was not cold-moist stratified. Seed germination was conducted under 16/8 h of light/dark at 25 °C and determined (A) at 3 d and (B) 10 days after removal from the stratification treatment. Control represents seeds germinated under 16/8 h of light/dark at 25 °C but with no stratification. Bars represent the standard error of the mean. Bars with different letters are significantly different at P = 0.05 according to Fisher's test.

Figure 2

Effect of light during cold-moist stratification on Echinacea (combined E. angustifolia, E. pallida, and E. purpurea) seed germination. The cold-moist stratification treatment consisted of 4 wk at 4 °C under either 24 h of light, 24 h of dark, or 16/8 h of light/dark. Control treatment was not cold-moist stratified. Seed germination was conducted under 16/8 h of light/dark at 25 °C and determined (A) at 3 d and (B) 10 days after removal from the stratification treatment. Control represents seeds germinated under 16/8 h of light/dark at 25 °C but with no stratification. Bars represent the standard error of the mean. Bars with different letters are significantly different at P = 0.05 according to Fisher's test.

Figure 3

Effect of light during cold-moist stratification on seed germination of E. angustifolia, E. pallida, and E. purpurea. Germination was counted 10 d after removal from the stratification treatment. Treatments during cold-moist stratification were 24 h of dark, 24 h of light, and 16/8 h of light/dark. After the stratification period, seeds were placed to germinate under 16/8 h of light/dark at 25 °C. Bars represent the standard error of the mean. Bars within each group with different letters are significantly different at P = 0.05 according to Fisher's test.