Cell-wall extension as a mode of action of coal-derived humates

A coal-derived sodium humate (HANa) was found to stimulate root growth of wheat seedlings (Triticum aestivum L.). A study of possible modes of action of HANa showed that (i) by chelating out ferrous iron, HANa sequestered a key participant from the reaction whereby proline is hydroxylated to hydroxyproline, resulting in significantly less hydroxyproline being formed in the cell walls of roots treated with HANa, and that (ii) HANa inhibited the activity of peroxidase and IAA oxidase, the inhibition of peroxidase being of the uncompetitive type. Since these effects have implications for the ability of root cells to undergo extension, it is proposed that they provide explanations for the stimulatory effect of HANa on growth