Allelopathy of the moss Rhynchostegium pallidifolium and 3-hydroxy-β-ionone.

The moss Rhynchostegium pallidifolium (Mitt.) A. Jaeger, which often forms large pure colonies on soils and rocks, inhibited the hypocotyls and root growth of cress (Lepidium sativum L.) seedlings when R. pallidifolium and cress were incubated to-gether on agar medium. The inhibition of cress was greater at the close position from the moss than at the far position from the moss. 3-Hydroxy-β-ionone was found in the medium and concentration of 3-hydroxy-β-ionone in the medium was greater at the close position than at the far position from R. pallidifolium, suggesting that R. pallidifolium may secrete 3-hydroxy-β-ionone into the medium. Exogenously ap-plied 3-hydroxy-β-ionone inhibited the growth of hypocotyls and roots of cress at con¬cen¬tra¬tions greater than 1 and 3 μM, respectively. Considering the growth inhibi-tory activity and concentrations found in the medium, 3-hydroxy-β-ionone was esti-mated to be able to cause 46 - 64 % of the observed growth inhibition of cress hypo-cotyls and roots by R. pallidifolium. Therefore, 3-hydroxy-β-ionone may play an important role in the allelopathic activity of R. pallidifolium and may help competi-tion with neighboring plants resulting in the formation of pure colonies.