The Effect Of Aluminum On Cell Wall Pectin, And The Role Of Nitric Oxide, Auxin In Al-induced Oxalate Secretion

In acid soil, the primary symptom of Al toxicity is rapid inhibition of root growth, however the mechanism of Al toxicity is still unclear. Eight buckwheat cultivars collected from 4 provinces were used to investigate the relationship between their relative root elongation, Al accumulation, content of pectin in root tips and its degree of methylation. The results indicated that Al limited the elongation of buckwheat root and Al accumulated in root immediately. Al content in root apex was positively correlated with Al content. Localization of pectin by immunofluorescence revealed that Al treatment resulted in the de-methylesterification of pectin. We suggest that binding of Al to carboxylic groups of pectin leads to the accumulation of Al and pectin, these processes finally resulted in the epidermal cell wall crack and root elongation inhibition as indicated by hematoxylin staining of roots.The role of nitric oxide and auxin in Al-induced oxalate secretion was also investigated in tomato roots. There was no significantly difference in NO content between plants with different Al treatments. NO donor SNP and scavenger cPTIO had no influence on Al resistance of tomato. On the other hand, the content of endogenetic auxin in root did not change with Al stress. The previous results in our lab indicated that Aluminum stimulated oxalate secretion from tomato roots in a dose- and time-dependent manner. Our results provided evidence that signaling path which NO and IAA might involved in was independent of Al-induced oxalate secretion. However, this result should be validated further.