Amyloplast sedimentation kinetics in gravistimulated maize roots |
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Authors: | Fred D Sack M Mitsu Suyemoto A Carl Leopold |
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Institution: | (1) Boyce Thompson Institute for Plant Research, Cornell University, 14853 Ithaca, NY, USA;(2) Present address: Department of Botany, Ohio State University, 1735 Neil Avenue, 43210-1293 Columbus, OH, USA |
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Abstract: | Amyloplast sedimentation in gravistimulated maize (Zea mays L.) roots was measured using the change in angle from the center of the cell to each amyloplast as an index of sedimentation. Using tissue fixed after gravistimulation, the relationship between mean amyloplast angle and the duration of gravistimulation was found to be linear when plotted on a logarithmic time scale. Extrapolated values for the onset of angular change are 5.9 s after the start of gravistimulation for the entire population of amyloplasts and 11.8 s for lead amyloplasts. By multiplying the instantaneous angular velocity (in radians) by the cell center to amyloplast radius, it is possible to calculate the initial sedimentation velocity to be 19.1 m min-1 at 5.9 s. During sedimentation, the mean amyloplast angles surpass the calculated cell corner angle of 123° at 2.2 min for all amyloplasts and at 19 s for lead amyloplasts near the new lower wall. Thus, substantial sedimentation occurs within the presentation time, calculated to be 4.1 min. These kinetics are consistent with several hypotheses of graviperception.Symbol tp
presentation time |
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Keywords: | Amyloplast sedimentation Root (gravistimulation) Graviperception Zea (graviperception) |
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