Effects of Osmotic Shock on Some Membrane-regulated Events of Oat Coleoptile Cells

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Abstract
Oat coleoptile sections (Avena sativa L. cv. Garry) were osmotically shocked with 0.5 M mannitol followed by 1 mM Na-phosphate (pH 6.4) at 4.degree. C. This treatment reduced uptake of .alpha.-aminoisobutyric acid, 3-O-methyl glucose and leucine by 75-90% but inhibited 36Cl-uptake only 30%. Some recovery was observed 1-3 h later. Respiration rates were unaffected by osmotic shock, and protein synthesis was reduced 11%. Osmotic shock also stimulated efflux of .alpha.-aminoisobutyric acid and K+ and led to an increase in conductivity of the solution bathing shocked sections. The transmembrane electropotential of 75% of the shocked cells fell to -20 mv to -45 mv compared with the majority of unshocked cells at -80 mv to -120 mv. Apparently osmotic shock selectively modifies the plasma membrane. The inhibitions of uptake could be due to removal of specific components of the plasma membrane and/or to the lowered electropotential.