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

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 CaCl(2) (1 and 10 millimolar) for 7 days, and then exposed to [(14)C]glucose for 5 hours. Uptake and incorporation of [(14)C]glucose into various cell wall fractions of the root tips were determined. At 1 millimolar Ca(2+), treatment with 150 millimolar NaCl slightly stimulated uptake but considerably inhibited glucose incorporation into noncellulosic and cellulosic polysaccharides. Supplemental Ca(2+) 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 Ca(2+) counteracts this effect. The effects on cellulose biosynthesis are proposed to be related to Ca(2+) displacement from the plasma membrane.