A Pressure-Jump Method as a New Tool in Growth Physiology for Monitoring Physiological Wall Extensibility and Effective Turgor

概要

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A new method has been devised in order to allow the rapid determination of the physiological extensibility (φ) of the cell wall together with the apparent effective turgor (P-Y'). The method consists of determining the elongation growth rate of a segment of pea hypocotyl with an auxanometer and applying a very small increase (around 10 kPa) in xylem pressure (jumps) by the xylem perfusion method. The cell turgor pressure is increased by the water surge from the xylem that is due to the pressure jump and reaches a new level within a short time. The elongation rate is also increased asymptotically to a new steady-state level within a short time. φ is estimated by simply dividing the increase in the steady-state growth rate by the increase in perfusion pressure, which is monitored by a pressure transducer or by the increase in turgor pressure measured by a pressure probe. Minimal length of the time period required to get a new steady elongation rate is 1.5 min. Therefore, it is possible to scan continuously the change in φ by the intermittent application of the brief, small pulses of xylem pressure during any experimental treatment. The apparent effective turgor P-Y' can be calculated by dividing the initial elongation growth rate by φ. Using this method, we have demonstrated experimentally the non-linearity of the relation-ship between elongation rate and turgor (Lockhart mechanical equation).
日本植物生理学会の論文