Potassium, not lepidimoide, is the principal ‘allelochemical’ of cress-seed exudate that promotes amaranth hypocotyl elongation

Imbibed cress ( Lepidium sativum L.) seeds exude 'allelochemicals' that promote excessive hypocotyl elongation and inhibit root growth in neighbouring competitors, e.g. amaranth ( Amaranthus caudatus L.) seedlings. The major hypocotyl promoter has recently been shown not to be the previously suggested acidic disaccharide, lepidimoic acid (LMA), a fragment of the pectic polysaccharide domain rhamnogalacturonan-I. The nature of the hypocotyl promoter has now been re-assessed.