Aluminum rapidly inhibits cellulose synthesis in roots of barley and wheat seedlings

The change in polysaccharide synthesis was studied in the roots of barley and wheat seedlings exposed to Al. Rapid inhibition of 14C-glucose incorporation into the cellulose fraction, which occurred within 15 min of Al exposure, occurred in both barley and wheat root cells. The reduction in cellulose synthesis was more severe in an Al-sensitive wheat cultivar (Scout 66) than in an Al-tolerant wheat cultivar (Atlas 66). From these results, it can be hypothesized that a reduction in cellulose synthesis causes the Al-induced rapid inhibition of root elongation. Coumarin, a potent inhibitor of cellulose synthesis, inhibited root elongation, which supports the hypothesis. Roots exposed to Al also showed a rapid enhancement of radioactivity incorporation into the hemicellulose fraction, which was attributed to the induction of callose formation. Callose was formed simultaneously with the inhibition of cellulose synthesis, in inverse proportion to the decrease in cellulose. Therefore, the cellulose synthesis system can be switched to a callose synthesis system in Al-injured root cells.