Momilactone A and B have been found only in rice and the moss, Hypnum plumaeforme, although both plants are taxonomically quite distinct. The endogenous concentrations of momilactone A and B in H. plumaeforme were 58.7 and 24.3 microg/g dry weight, respectively. UV-irradiation increased the concentrations of momilactone A and B. The concentrations of momilactone A and B, respectively, became 14- and 15-fold greater than those of non-UV-irradiated control. CuCl2 and FeCl2 (1 mmol/L) treatments also increased momilactone A and B concentrations by 2.7- to 6.1-fold and 2.9- to 6.3-fold, respectively. In addition, the protein phosphatase inhibitor, cantharidin, and jasmonic acid increased momilactone A and B concentrations in H. plumaeforme. Cantharidin acts as an elicitor and jasmonic acid is an important signaling molecule regulating inducible defense genes against the pathogen infection. Momilactone A and B, respectively, were increased 12- and 11-fold by 200 micromol/L cantharidin, and 14- and 15-fold by 100 micromol/L jasmonic acid compared with non-treated controls. As momilactone A and B are phytoalexins, these compounds may play an important role in defense responses against biotic and abiotic stress conditions in H. plumaeforme.

Summary Extract of soil under colonies of Hypnum plumaeforme inhibited the growth of roots and shoots of cress, lettuce, lucerne, ryegrass, timothy, Digitaria sanguinalis and Echinochloa crus‐galli. Increasing the extract concentration increased the inhibition, which suggest that the soil may contain growth inhibitory substances and possess allelopathic potential. The extract of the soil under H. plumaeforme was purified and two main inhibitory substances were isolated and determined by MS and 1H‐ and 13C‐NMR spectral data as momilactone A and B. Momilactone A and B inhibited hypocotyls and roots of cress seedlings at concentrations >10 and 1 μm respectively. The endogenous concentration of momilactone A and B in H. plumaeforme was 58.7 and 23.4 μg g−1 dry weight respectively and the concentration of momilactone A and B in MS growth medium of H. plumaeforme was 4.3 and 6.4 μg g−1 dry weight of H. plumaeforme, respectively. These results suggest that momilactone A and B were probably secreted into the medium during the incubation and momilactone A and B found in the soil under H. plumaeforme may have been released by the moss. Therefore, growth inhibitory activity of the soil under H. plumaeforme may be caused by momilactone A and B, which may act as allelopathic agents of H. plumaeforme.

No abstract

No abstract