Peter Melcher was invited to present, “Mission Impossible: Moving Water against the Forces of Evil (Gravity and Resistance) in Plants”. Seminar Series, Biology Department, Colgate University. September 2012.
In this presentation, I explained how water moves through a plant, and how plants have evolved to overcome the “evil” forces of hydraulic resistance and gravity without using a positive force pump. I also presented observations from Magnetic Resonance Imaging studies used to view embolism refilling while all surrounding water is at negative water potentials. The mechanisms that allow plants to refill embolisms while under tension has stumped physiologists since the first observations of embolism refilling 15 years ago. I also provided potential mechanisms that describe how this process might work.
Figure 5. A. Images are real time MRI observations of an intact stem section of moderately stressed A. rubrum plant. Images show the development of spontaneously occurring embolism (6 min) and its spread across the current growth ring (18 min) followed by almost full water contentment recovery (30 min). B. These images are accompanied by three dimensional analyses of embolism formation, its spatial spread and recovery. Blue color denotes embolus.