Olfactory responses of Phycomyces blakesleeanus

Upon exposure to low levels of various volatile compounds such as n-heptanol, methanol, CHCl₃, mercaptoheptane, etc., the sporangiophore of Phycomyces blakesleeanus responds with a transient and reproducible decrease in its elongation rate. All 22 volatile substances tested (except H₂O) elicited negative responses. The amplitude of the responses depends on the compound and its concentration. A characteristic concentration, required for 50% inhibition, correlates remarkable well with the human olfactory threshold (coefficient of correlation r = 0.89 (P < 0.001)). Perhaps some process in olfaction is common to this fungus and higher systems.