Incorporation of [14C]Glucose into Cell Wall Polysaccharides of Cotton Roots: Effects of NaCl and CaCl2

Abstract

Cotton (Gossypium hirsutum L. cv Acala SJ-2) seedlings were grown in nutrient solutions with four combinations of NaCl (0.1 and 150 millimolar) and CaCl₂ (1 and 10 millimolar) for 7 days, and then exposed to [¹⁴C]glucose for 5 hours. Uptake and incorporation of [¹⁴C]glucose into various cell wall fractions of the root tips were determined. At 1 millimolar Ca²⁺, treatment with 150 millimolar NaCl slightly stimulated uptake but considerably inhibited glucose incorporation into noncellulosic and cellulosic polysaccharides. Supplemental Ca²⁺ did not affect incorporation of glucose into the noncellulosic fraction (regardless of NaCl treatment) but completely alleviated the inhibitory effect of NaCl on glucose incorporation into cellulose. We suggest that high Na⁺ concentrations reduce synthesis of cellulose in cotton roots via disturbance of plasma membrane integrity and that supplemental Ca²⁺ counteracts this effect. The effects on cellulose biosynthesis are proposed to be related to Ca²⁺ displacement from the plasma membrane.