Submitted to: Global Change Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/25/2005
Publication Date: 6/1/2005
Citation: Ziska, L.H., Emche, S.D., Johnson, E.L., George, K., Reed, D.R., Sicher Jr, R.C. 2005. Alterations in the production and concentration of selected alkaloids as a function of rising atmospheric carbon dioxide and air temperature: Implications for Ethno-pharmacology. Global Change Biology. 11: 7198-1807.
Interpretive Summary: Many chemicals produced by plants are used to ward off insects or mammals that eat them (herbivory). These same chemicals are also recognized as impacting (either positively or negatively), human physiology. How will a changing climate, most notably the documented increase in global temperature and carbon dioxide, alter the production of these chemicals? To understand this, we looked at three different chemicals, atropine, scopolamine and nicotine from two different plant species, jimson weed and tobacco. We used carbon dioxide (CO2)values that corresponded to the concentrations in the earth=s atmosphere that existed at the beginning of the 20th century, current values, and those projected for the year 2050 and temperature values projected for the next 20-40 years. We report here that any increase in CO2 resulted in a significant increase in leaf area and growth, while increased temperature resulted in earlier plant development and greater leaf area for both plant species. We also determined that increasing CO2 reduced the concentration of nicotine in tobacco; but had no effect on atropine, and increased the concentration of scopolamine in jimson weed. Conversely, temperature had no effect on nicotine or scopolamine concentration, but significantly increased the concentration and amounts of atropine per plant. However, because of the stimulatory effect of CO2 on growth, all three secondary compounds increased on a per plant basis (at either temperature) in both species. Overall, these data suggest that increases in CO2 and temperature associated with global climate change may have significant effects not only with respect to herbivory, but on the production of secondary compounds by plants that may impact human physiology. Data from this study will therefore be of benefit to entomologists, pharmacists, biochemists and ethnobotanists.
Technical Abstract: After harvesting, all replicated samples of D. stramonium were oven dried @ 40°C for 48 hrs to ensure complete dryness. Extraction and analysis of all samples were as described by Johnson and Emche (1994) except for modifications as follows. A 100 mg (d. wt) sample of each sample was individually ground and extracted in a Pierce Reacti-Therm III heating/stirring module (Pierce Biotechnology Inc., Rockford, IL, USA) with 95% EtOH and a conical stir bar. Samples were boiled for 25 minutes @ 85°C, allowed to cool, the solute removed and re-extracted. Solutes were combined and roto-evaporated to dryness at 40°C. Samples were redissolved in 2 ml HPLC grade MeOH, filtered through a 0.2µm syringe filter and stored at 4°C until GC-MS analysis. Gas chromatography was performed on a Hewlett-Packard 6890A GC, including an HP 7673A autosample injector and Chemstation software (Hewlett-Packard, Avondale, PA, USA). GC conditions were as follows: detection: MS; detector heater: 300°C; scanning mass range: 50-550 mass units @ 1.61 scans/second; carrier gas; UHP He; column flow rate 1.2 ml/min; column: DB-5 (5% Phenyl), 30m x 0.25 mm i.d., 0.25 µm film thickness(Phenomenex, Torrance, CA, USA); injection temperature: 275°C; programmable oven temperature: 50-300°C in increments of 30°C/min.; run time 11.33 min.; injection volume 2µl in splitless mode. Four point standard curves of atropine and scopolamine (Sigma Chemical Co., St. Louis, MO, USA) were used for quantitation. Confirmation of the standards and plant alkaloid extracts were made by GC-MS spectral analysis.