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Apocynum cannabinum: effect of light intensity on anthocyanin production

David Furman and Dana Dudle
Biology Department and Science Research Fellows, DePauw University
Summer 2006

Anthocyanins are pigment molecules that produce red, purple, and blue colors in plants. Production of anthocyanin is triggered in response to stress.  A research project conducted in 2005 showed that there was a significant relationship between light intensity and anthocyanin production in Apocynum cannabinum growing in the Quarry Bottom.  Our project addresses several questions as a follow-up from this previous research:  (1) Does light intensity have a direct impact on anthocyanin production in the stem of Apocynum?  (2) Can the color of Apocynum be manipulated within the field by reducing the amount of light they receive?  (3) How accurate is the reflectance spectrometer in the field?

We measured light intensity and stem color in 61 patches of Apocynum scattered throughout the Quarry Bottom.  We also measured light intensity and stem color of plants in in response to an experimental shade treatment.  Light intensity was measured in micromoles (μmol) of photons.  Anthocyanin levels in the plant stems were measured with a field spectrophotometer. 

Results and Discussion
Light intensity was a significant predictor of anthocyanin production in Apocynum in the Quarry Bottom.  Light intensity explained 18 percent of the observed variation in anthocyanin production.  Anthocyanin production also varied in response to experimental manipulation of light.  After 6 weeks, plants in shaded conditions produced significantly less anthocyanin than plants in the sun.  Our research showed that there is a large amount of variation in anthocyanin production that is not explained by light intensity.  Future studies should focus on other environmental stress factors that may contribute to anthocyanin production of Apocynum .  Potential factors include water availability, nutrient availability, and genetic variation of plants.