ARS | Publication request: ALLELOPATHIC EFFECTS OF VOLATILE CINEOLES ON TWO WEEDY PLANT SPECIES

Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 13, 1999
Publication Date: N/A

Interpretive Summary: Many plants produce defense chemicals against competing plants. In our quest to produce environmentally friendly herbicides, it is necessary to understand how these natural compounds work. We looked at two similar natural products that often occur together. One compound, 1,8-cineole arrested mitosis and decreased seed germination, while the other compound, 1,4-cineole severely decreased growth of roots and shoots and the ability of plants to do photosynthesis. Although they appear to be the same in terms of chemical components and highly similar in structure, their mechanisms of action are very different.

Technical Abstract: The volatile monoterpene analogs, 1,4-cineole and 1,8-cineole, have been identified as minor components of many plant essential oils, but little is known about their biological activities. We compared the effects of 1,4- and 1,8-cineole on two weedy plant species by monitoring germination, mitosis, root and shoot growth, chlorophyll content and photosynthetic efficiency. 1,4-cineole severely inhibited growth of roots and shoots, causing cork-screw shaped morphological distortion, whereas 1,8-cineole caused a decrease in root growth and germination rates. Chlorophyll fluorescence data (yield and Fv/Fm) indicated that 1,4-cineole caused significantly higher stress (p<0.001) to photosynthesis when compared to controls. Mitotic index data showed that 1,8-cineole severely decreased (p<0.001) all stages of mitosis when compared with controls, while 1,4-cineole only decreased prophase (p<0.05). Although superficially similar in structure, these two cineoles appear to have different modes of action.