Promotion of cress root elongation in white light by 3,5-diiodo-4-hydroxybenzoic acid.

The effect of low concentrations of 3,5-diiodo-4-hydroxybenzoic acid (DIHB) in promoting the elongation of light-exposed cress (Lepidium sativum L.) roots has been further examined. Aeration of the DIHB solution in which the roots were grown largely removed the growth promotion. The addition of ethylene or the ethylene precursor methionine to the solution caused marked inhibition of root elongation and this effect was relieved by DIHB.