Effect of Water Stress on Cell Wall Metabolism of Avena Coleoptile Tissue

Abstract

A period of salt absorption by coleoptile sections in solutions with high (equivalent to 0.35 [image] mannitol) diffusion pressure deficits (DPD) causes an increase in turgor and an increase in incorporation of C14 from glucose-C14 into all fractions of the cell wall in experiments of short duration. The increases in incorporation are similar to those obtained when turgor is increased by reducing DPD of the external mannitol solutions. The sugar components of the wall fractions become radioactive and appear to be affected by treatments in the same general way as the total activity of the fractions concerned. In sections in which turgor pressure has increased from a low value to one approaching full turgor (equivalent to 0.4 M mannitol) there is a tendency for the metabolism of the acid and dilute alkali soluble wall constituents to be stimulated, compared with that in sections maintained at constant full turgor. The rate of elongation and amount of incorporation of C14 into cellulose show rather similar patterns of behavior with respect to effect of osmotic factors. It is suggested that turgor is the chief component of DPD affecting elongation and incorporation into the cell wall, and that some aspect of cellulose synthesis may be involved in the elongation response to turgor in Avena coleoptiles.