Rhubarb: More Than a Delicious Pie Filling

By Mason MacDonald, Science Journalism Intern

Rhubarb petioles make a tart (but delicious) pie filling or jam. However, a large portion of a rhubarb plant must remain unused, as the leaves contain higher concentrations of poisonous oxalic acid. Unfortunately the unused rhubarb leaves also contain a bounty of natural antioxidants, compounds proven to help inhibit the production of free radicals often linked to cancer and aging. Valuable antioxidants such as auronols, carpusins, maesopsins, anthraquinones, and phenolics are being discarded everyday, but that may come to a stop if former Nova Scotia Agricultural College (NSAC) student Andrea Munroe has her way.

Munroe received a research award from the Natural Sciences and Research Council of Canada (NSERC) that allowed her to work on campus for the summer, studying the effects of rhubarb leaf extracts as a seed preconditioning agent. A seed preconditioning agent is a compound, or group of compounds, that when applied to a seed can induce a physiological change that may confer benefit to a developing plant. Under the guidance of Dr. Raj Lada and the Rhubarb Research Program, Andrea developed the hypothesis that naturally occurring antioxidants could help induce drought protection in carrots. Munroe credits Dr. Lada in helping develop her research interest and raise her awareness of NSERC.

“I took a crop adaptation course from Dr. Lada and he approached me about applying for an undergraduate student research award from NSERC,” says Munroe.

The objective of Munroe’s research was to test the effect of a broad range of extract concentrations from two different extraction methods, one using water and the other using ethanol. She measured multiple parameters, including changes in photosynthesis, height, dry mass, and membrane injury. Munroe was very eager to aid in the development of this technology and believes it will eventually be able to help producers.

“I was hoping that farmers could eventually treat their seeds themselves. I didn’t really want to invent anything, but thought it would be cool to uncover another tidbit of information that could help farmers out - especially a product that could be available for organic farmers.”

There were mixed results from Munroe’s study. The rhubarb leaf extracts had no effect on photosynthesis, increased leaf weight, but decreased root weight and plant height. Overall, Munroe found that her extracts were able to help mitigate drought, but resulted in slightly stunted growth. However, most commercially available products to help prevent drought also result in decreased growth and can sometime also result in increased mortality or toxicity. Munroe’s discovery did not indicate either condition and it can be used by organic farmers.

Although Munroe’s new discovery is exciting, there are several studies remaining before this technology could be widely available. She claims that subsequent studies will try to narrow the range of extract concentrations in order to determine an ideal concentration to mitigate drought. Munroe also claims that longer drought studies are needed, to determine the long range effects of growth parameters during and after drought. In addition, Munroe suggests that a study should be conducted to verify that there is not a dangerous increase in the oxalic acid concentrations in treated plant tissue.

Munroe described both her experience at the NSAC and working with NSERC as “great”. She claims NSERC helped give her research experience in a “real-life” environment and allowed her to see how to apply courses from the NSAC. Since completion of her research project, Munroe graduated from NSAC in May 2006 and is working for the Organic Agriculture Center of Canada.