Polarity of Water Transport across Epidermal Cell Membranes in Tradescantia virginiana      

Abstract

Using the automated cell pressure probe, small and highly reproducible hydrostatic pressure clamp (PC) and pressure relaxation (PR) tests (typically, applied step change in pressure = 0.02 MPa and overall change in volume = 30 pL, respectively) were applied to individual Tradescantia virginiana epidermal cells to determine both exosmotic and endosmotic hydraulic conductivity (L p OUT and L p IN , respectively). Within-cell reproducibility of measured hydraulic parameters depended on the method used, with the PR method giving a lower average coefficient of variation (15.2%, 5.8%, and 19.0% for half-time, cell volume [V o ], and hydraulic conductivity [L p ], respectively) than the PC method (25.4%, 22.0%, and 24.2%, respectively). V o as determined from PC and PR tests was 1.1 to 2.7 nL and in the range of optically estimated V o values of 1.5 to 4.9 nL. For the same cell, V o and L p estimates were significantly lower (about 15% and 30%, respectively) when determined by PC compared with PR. Both methods, however, showed significantly higherBecause these results were obtained using small and reversible hydrostatically driven flows in the same cell, the 20% outward biased polarity of water transport is most likely not due to artifacts associated with unstirred layers or to direct effects of externally applied osmotica on the membrane, as has been suggested in previous studies. The rapid reversibility of applied flow direction, particularly for the PR method, and the lack of a clear increase in L p OUT /L p IN over a wide range of L p values suggest that the observed polarity is an intrinsic biophysical property of the intact membrane/protein complex.

Turgor-responsive starch phosphorylation in Oryza sativa stems: A primary event of starch degradation associated with grain-filling ability

“…Furthermore, it has been reported that 0.2 MPa of pressure differences induce plasmodesmatal closure in Nicotiana clevelandii cells [ 27 ]. Significant decreases in membrane hydraulic conductivity have been observed at 1 min after 0.1–0.2 MPa of hydraulic disturbance was instantly given [ 28 , 29 ]. Hence, if turgor pressure was altered in a cell, the hydraulic pressure differential would be rapidly transmitted to the nucleus and other organelle compartments.…”

Pico Gauges for Minimally Invasive Intracellular Hydrostatic Pressure Measurements

“…The cell pressure probe is an excellent tool to acquire data on parameters such as cell turgor, cell wall elasticity, and membrane permeability and has been optimized for a number of cell types over the last decades (Steudle and Zimmermann, 1977;Hüsken et al, 1978;Cosgrove 1981Cosgrove , 1985Cosgrove , 1993Shackel and Brinckmann, 1985;Cosgrove et al, 1987;Oparka et al, 1991;Ye and Steudle, 2006;Wada et al, 2014). Unfortunately, some cell types show rapid injury responses, which make it difficult or impossible to apply this method.…”

Dynamics and stabilization mechanism of mitochondrial cristae morphofunction associated with turgor-driven cardiolipin biosynthesis under salt stress conditions

“…In some cases, wall elastic modulus ( ε ) and cell hydraulic conductivity ( L p ) were measured with a CPP in control cells ( T = 0 h). By applying < 0.1 MPa of pressure pulses, ε was determined by ε = V·ΔP/ΔV after the Ψ p measurement according to the previous studies 29 , 64 . The L p is given by L p = ln(2) V /( AT 1/2 ( ε + π )) 29 , where A is the cell surface area, and π is the cell osmotic pressure (i.e., − Ψ s ) determined with the nanoliter osmometer.…”