I am proposing an exploratory project to try to better understand water mechanics in plants. I believe that in order to truly understand the dynamics of water storage and transport in plants, the structures that are involved should be understood in 3 dimensions. This project will start by using a Nikon AZ100 microscope with a Griffax video camera and Jenoptik Z-stack software for the 3-dimensional imaging of Sphagnum hyaline cells. These water storage structures typically have pores through which air will enter as a bubble through the largest pore that is exposed to external air as the plant dries. Release of the water by embolism in the hyaline cells allows the photosynthetic cells to remain hydrated longer. Presumably, a collection of hyaline cells with a graded series of largest pore diameters will allow an individual plant to dehydrate slowly over time and permit photosynthetic cells to function over much of the extended time. The project will progress by trying to capture bubble entry in 3 dimensions. Sphagnum girgensohnii Russow will serve as the first test subject because the hyaline cells have characteristics that make following the embolism process fairly easy. For that reason, I used S. girgensohnii in my initial work to document that the pressures at which bubbles pull through the largest micron-scale pore in hyaline cells as they embolize fit the predictions of Newtonian physics (Lewis AM 1988). This work is an extension of those experiments. If successful in capturing embolism in S. girgensohnii, I will attempt to do the same in other species of Sphagnum where visualization of the process is more difficult because of the structure of the hyaline cells and basic plant anatomy, such as the physical relationship of the hyaline cells to the photosynthetic cells.
Completing 3-D imaging of embolism in Sphagnum is a precursor to attempting to do so in the woody conduits of trees using higher magnification microscopes.
I plan to let other researchers have access to the microscope with my permission and training.
Lewis AM 1988 A Test of the Air-seeding hypothesis using Sphagnum
hyalocysts. Plant Physiol 87: 577-582