The Growth Response of Ecotypes of Holcus lanatus L. from Different Soil Types in Northwestern Europe to Phenolic Acids

Abstract: Phenolics are often discussed in relation to either allelopathy or to herbivory. This work, however, was undertaken to determine if phenolic acids benefit the growth of plants in very acid soils. We here report racial differences in the phenolic acid concentrations of the important plant species found in five sites within Central Scotland which covered a wide range in soil acidity from very acid (organic peats) to mildly acid (calcareous), and describe the racial differences in the growth response of Holcus lanatus L. to phenolic acids with increasing acidity. The total concentrations of phenolic acids in the ecotypes of important species were correlated with the total concentrations found in their respective soils. In general, the most phenolic-rich ecotypes of the five came from the organic acid soils (Flanders Moss FM] and Sheriffmuir SMB]). However, with the exception of ferulic acid which was a major component of both acid soils and their associated vegetation, individual simple phenolic acids extracted from either plants or soils were not consistently correlated. The addition of dry plant material collected from the five sites (0.5 g plant material 100 g^-1 soil) to the acid-organic Flanders Moss (FM) soil stimulated the growth of two ecotypes of Holcus (acid-mineral Sheriffmuir SMM], calcareous Kinloch Rannoch KR]) but the same litter addition in non-organic, less acidic or calcareous soil inhibited growth of these ecotypes. In hydroponic solutions, growth response of Flanders Moss (FM) and Kinloch Rannoch (KR) to pH and phenolic acid mixtures was interdependent: in acid solutions (pH 4.0) but not at pH 6.5 root elongation rates (RER) of both ecotypes, and shoot elongation rates (SER) of Flanders Moss (FM), increased after treatment with a mixture of seven commonly occurring phenolic acids.