Light-activated plant growth inhibitory activity of cis-dehydromatricaria ester, rose bengal and fluoren-9-one on lettuce (Lactuca saliva L.)

The polyacetylene allelopathic compound cis-dehydromatricaria ester (cis-DME) was extracted from the roots of goldenrod, Solidago altissima L. cis-DME strongly inhibited the growth of lettuce (Lactuca saliva L. c. v. sacramento) on its radicles and hypocotyls in the presence of light whereas less or no significantly different effects were observed in the dark. The light-activated plant growth inhibitory (PGI) activity of cis-DME was more obvious in lettuce hypocotyls than in radicals. Its PGI activity was compared with the known phototoxic compounds rose bengal and fluoren-9-one. Although the light-activated PGI of cis-DME was not as high as that of rose bengal, and the dose-response relationship was slightly different with those of rose bengal and fluoren-9-one, cis-DME showed a very typical pattern of light-enhanced PGI activity against lettuce seedlings. The inhibition on the growth of lettuce radicles and hypocotyls highly enhanced by the presence of light. A growth enhancement effect was also observed on the radicles of lettuce when treated with lower concentrations of fluoren-9-one. A photosensitization mechanism is proposed here that the PGI activity of cis-DME may involve photosensitization and active oxygen such as singlet oxygen.