PLANT PHYSIOLOGY , Vol 108, Issue 3 1251-1258, Copyright © 1995 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Evidence for Mass Flow in Flowering Individuals of the Submersed Vascular Plant Myriophyllum heterophyllum
J. L. Schuette and M. J. Klug
Kellogg Biological Station, Michigan State University, Hickory Corners, Michigan 49060
Myriophyllum heterophyllum Michx. is a rhizomatous submersed aquatic plant
that produces a short, emergent floral spike. We hypothesized that lacunar
pressures in emergent spikes should be at or near atmospheric pressure and
that a mass flow of gases from submersed stems through the rhizome to
emergent stems may occur as lacunar O2 concentrations and pressures in
submersed stems increase during photosynthesis. We examined the potential
for a pressure gradient ([delta]P) to develop along this pathway by
measuring diurnal changes in lacunar gas composition and pressure in
submersed stems of nonflowering plants and emergent stems of flowering
individuals. Methane release from emergent spikes was also monitored during
three diurnal cycles to evaluate the hypothesis that the [delta]P is
maintained by the release of lacunar gases to the atmosphere. Lacunar O2
concentrations and pressures in submersed stems increased at sunrise and
reached maximum levels by midday. Although O2 fluctuated similarly in
emergent stems, lacunar pressures remained at or near atmospheric pressure,
indicating that a [delta]P is generated between submersed and emergent
stems during photosynthesis. Methane release from emergent spikes increased
as lacunar pressures increased, indicating that rhizome gases are
transported through emergent stems by mass flow and the [delta]P is
maintained by venting lacunar gases from emergent spikes. The potential for
mass flow in both flowering and nonflowering individuals is discussed.
