Role of phenolic acids in expression of barley (Hordeum vulgare) autotoxicity

The role of phenolic acids in autotoxicity of four barley (Hordeum vulgare L.) varieties was investigated using radicle growth bioassays and analytical techniques. Total phenolic content of barley plant components varied within and between varieties during the 1999–2002 growing seasons. Inhibition of barley radicle growth was positively correlated with total phenolics depending on growing season and variety. Only total phenolic content of barley stems contributed significantly to barley autotoxicity. Concentrations of five phenolic acids differed in all plant components, among barley varieties and growing seasons. Ferulic acid and vanillic acid occurred least and most frequently in barley plant tissues, respectively; p-hydroxybenzoic acid, syringic acid, and p-coumaric acids were positively associated with barley autotoxicity (r ≥ 0.31). Inhibition was significantly correlated with total phenolics, although other allelochemicals could also contribute to barley autotoxicity. Variations in total phenolics and phenolic acid composition over growing seasons may indicate a strong impact of climatic conditions on phenolic accumulation in barley plants.