The growth of wheat plants in humic acid solutions under axenic conditions

Summary A technique is described for growing wheat plants in nutrient solutions containing C¹⁴-labelled humic acid under axenic conditions. The general appearance of axenic plants was indistinguishable from plants grown in association with microbes. C¹⁴-labelled humic acid enhanced the growth of both roots and shoots showing that by-products of microbial degradation of humic acid are unnecessary for this enhanced plant growth. Thus humic acid had a direct effect on the growth processes. The C¹⁴-labelled humic acid was taken up by the roots and virtually none was transported to the shoot. Only some 30 to 40 per cent of the incorporated radioactivity was associated with the root cell walls and thus more than 60 per cent was in the cytoplasm and may have influenced the biochemical processes involved in the regulation of plant growth.