Hormesis in Bioassyas of Macroalgal Fungal Propagules

Abstract

A range of dilutions (1:1 to 1:320) of ethanolic extracts of dried tissues of the macroalgae, Osmundaria serrata and Zonaria subarticulata were made. These dilutions were incorporated into fungal growth media and their influence on the germination of spores of Aspergillus niger and Alternaria sp., and the colony growth of Rhizoctonia solani after breaking of scerotial dormancy, observed. Pure ethanol inhibited spore germination and colony growth by up to 100%, but the toxicity of ethanol decreased with increasing dilution and showed hormetic trends. The presence of macroalgal factors ameliorated the toxicity of pure ethanol to different percentages but showed both amelioratory and inhibitory influences on the action of the different dilutions of ethanol on spore germination or colony growth. The data are discussed in the light of other examples of hormesis and the need to isolate the active macroalgal factors.