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Apocynum cannabinum: anthocyanin expression over a three day period

Erica Ross, Ryan Edelen, Matthew Howes and Dana Dudle
Science Research Fellows and Biology Department, DePauw University
Summer 2006

Our previous research has shown that Apocynum cannabinum stems produces more anthocyanin pigment in response to direct sunlight.  The goal of this experiment was to observe how anthocyanin production of Apocynum cannabinum is affected by sunlight over a short period of time.

We hypothesized that there would be differences among individuals and that there would be a change in the anthocyanin production of plants over a short period of time.

We selected 12 Apocynum cannabinum plants.  We assessed initial stem color of the 7th internode of each plant with a reflectance spectrophotometer.  We collected data on stem color four times a day for three consecutive days. 

All plant stems showed an increase in anthocyanin production over the three day period.  Overall, the amount of redness increased 42 percent over three days.  We also observed substantial variation among individuals.  The redness of one plant increased 84 percent whereas the redness of another plant increased by only 5 percent.  The plant stems also showed occasional reductions in redness.  The redness of the plant stems was not immediately affected by the amount of photosynthetically active radiation (PAR).  There was a time lag between the amount of PAR and stem redness.

We recommend repeating the experiment on a larger scale with a larger sample size and more frequent data collection, including at night.  It would be interesting to observe genetically similar plants to assess the effect of sunlight on plants.  Future work should also investigate the fluctuations in redness seen in some individuals.  This pattern may be explained by environmental effects such as degradation of chlorophyll or a decrease in anthocyanin production in response to decreased PAR.  Experimental error may also explain the reductions in redness over time.