Poster: Growth
Abs #
P27009: Elongation growth and turgor pressure of stage IVb sporangiophores of Phycomyces blakesleeanus during anoxia
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Presenter: |
Ortega, Joseph K.E. Contact Presenter |
Authors | Olson, Jessica E.C. (A) Ortega, Elena L. (A) Ortega, Joseph K.E. (A) | | Affiliations: |
(A): Bioengineering Laboratory, Department of Mechanical Engineering, University of Colorado at Denver
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The stage IVb sporangiophore of Phycomyces blakesleeanus consists of a cylindrical stalk with a spherical sporangium on top. The stalk is a single cell (0.1-0.2 mm in diameter and 2-10 cm in length) that elongates vertically from its mycelium at a rate of 30-50 μm min-1. In this study, elongation growth and turgor pressure of the stalk were measured during anoxia (the atmospheric air is replaced with nitrogen gas in a chamber containing the growing sporangiophore). When the oxygen concentration is reduced from 21% to less than 1%, the elongation growth rate immediately decreases and then becomes zero in a time interval that varies between 5 min and 50 min. Subsequently the elongation rate becomes negative, i.e. the stalk begins to decrease in length (shrink). The shrinking continues until the stalk buckles in the growth zone and the sporangium falls over to rest on the side of the stalk. Turgor pressure measurements with the pressure probe demonstrate that an immediate and sharp decrease in turgor pressure occurs when the oxygen concentration is reduced from 21% to less than 1%. Subsequently, the turgor pressure continues to decrease. In some cases, the subsequent decrease in turgor pressure is nearly exponential. In other cases, the subsequent decrease in turgor pressure is gradual for a period of time before it begins decreasing exponentially. In general, the immediate decrease in elongation rate coincides with the immediate and sharp decrease in turgor pressure. The subsequent relationship between the elongation rate and turgor pressure decay is varied and complex. However, the observed negative elongation rate (shrinking) can be interpreted as recovered elastic extension resulting from the turgor pressure decay.
