The effects of environmental stress on the production of anthocyanins in Apocynum cannabinum
David T. Furman and Dana A. Dudle
Biology Department, DePauw University
Anthocyanins are elaborate pigment molecules that give an array of land plants their red, purple, and blue coloring (Lee and Gould 2002). Production of anthocyanin is sometimes triggered in response to a stress caused within the habitat. A research project from 2005 demonstrated that there was a significant relationship between the extreme light intensity stress of the DePauw Nature Park’s limestone quarry and anthocyanin production in the stem of Apocynum. cannabinum. Our project addresses several questions as a follow-up from this previous research:
- Does light intensity have a direct impact on production of anthocyanin in the stem of Apocynum cannabinum?
- Can the color of Apocynum cannabinum be manipulated within the field by reducing the amount of light they receive?
- How accurate is the reflectance spectrometer in the field?
Light intensities were measured in micro-moles (μmol) of photons. Anthocyanin levels in the stem were estimated by examining the reflectance spectrum of the stem using a field spectrometer focusing on particular nodes on the stem of Apocynum cannabinum. The wavelengths that are pertinent to anthocyanins were analyzed with an equation to look specifically at an index of anthocyanin pigment.We measured light intensity and stem color at 61 patches of Apocynum cannabinum scattered throughout the quarry bottom. Our analysis showed that that light intensity was a significant predictor of anthocyanin production in Apocynum cannabinumgrowing in the quarry bottom. The light intensity experienced by focal plants explained approximately 18% of the observed variation in anthocyanin production. We also measured light intensity and stem color in plots manipulated by a shade reduction treatment. We found that pigment production responded to manipulation of light in the field. After 6 weeks, the shade plants produced significantly less pigment than the sun plants.
The experiment conducted in 2005 extracted pigments for analysis through destructive techniques, but in 2006, we used the reflectance spectrometer to obtain similar results through a non-destructive procedure. Our experiment also showed that there is a large amount of variation in anthocyanin production that is not accounted for within the plant populations in the Nature Park.Future studies should focus on other environmental stress factors that may contribute to production of anthocyanins within the stem of Apocynum cannabinum. Potential factors include water availability, nutrient availability, and genetic variation of plants among different sectors of the quarry bottom.