1,8-CINEOLE INHIBITS ROOT-GROWTH AND DNA-SYNTHESIS IN THE ROOT APICALMERISTEM OF BRASSICA-CAMPESTRIS L

1, 8-cineole is a volatile growth inhibitor produced by Salvia species . We examined the effect of this allelopathic compound on the growth o f other plants using Brassica campestris as the test plant. Cineole in hibited germination and growth of B. campestris in a dose-dependent ma nner. When B. campestris was grown for 5 days with various concentrati ons of cineole, the length of the roots was found to be shorter as the concentration of cineole increased, whereas the length of the hypocot yl remained constant up to 400 mu M cineole, indicating that cineole s pecifically inhibited growth of the root. The mitotic index in the roo t apical meristem of 3-day-old seedlings decreased from 5.6% to 1.6% w hen exposed to 400 mu M cineole, showing that cineole inhibits the pro liferation of root cells, We then examined the effect of cineole on DN A synthesis by indirect immunofluorescence microscopy using antibody r aised against 5-bromo-2'-deoxyuridine (BrdU, an analogue of thymidine) in thin sections of samples embedded in Technovit 7100 resin. The res ults clearly demonstrated that cineole inhibits DMA synthesis in both cell nuclei and organelles in root apical meristem, suggesting that ci neole may interfere with the growth of other plant species by inhibiti ng DNA synthesis in the root apical meristem.