The results of this study reveal that sorgoleone, after formulation as a WP, is more effective in inhibiting weed growth, and crop species are tolerant to it. The strong weed suppressive ability of formulated sorgoleone therefore offers interesting possibilities as an effective natural environment-friendly approach for weed management.

Fagopyrum tataricum Gaertn (tartary buckwheat) is an excellent medicinal and nutrient-rich crop. It has a high content of rutin and other phenolic compounds. An experiment was conducted to investigate in vitro production of phenolic compounds from hairy root culture of tartary buckwheat. Hairy root growth was promoted by increasing culture time in MS medium. The highest hairy root growth reached up to 11.2 g/l dry weight at 18 d after placement. Transformation was confirmed by PCR using rol genes, rol A (304 bp), B (797 bp), C (550 bp), and D (1035 bp) genes which is transferred into hairy roots from the Ri-plasmid in Agrobacterium rhizogenes and is responsible for the induction of hairy root from plant species. Rutin, quercetin, (-) epicatechin, (-) catechin hydrate, gallic acid, ferulic acid, chlorogenic acid, and caffeic acid were identified both in hairy and wild type roots of tartary buckwheat. The main compound found in the both types of root was epicatechin followed by rutin. The concentration of phenolic compounds in the hairy roots of tartary buckwheat was several-fold higher compared with wild type roots of same species. Our results indicate that hairy root culture of F. tataricum is a valuable alternative approach for the production of phenolic compounds.

Sorgoleone, found in the root exudates of sorghum [(Sorghum bicolor (L.) Moench], has been a subject of continued research. Sorgoleone production in grain sorghum roots was investigated under different growth conditions. Methanol was the most effective solvent for extracting sorgoleone from grain sorghum roots. Sorgoleone production is high in young developing plants. The maximum concentration (microg mg(-1) root dry weight) was produced in 5-d-old seedlings; beyond this age, production declined. However, considering both root weight and sorgoleone content per seedling, 10-d-old seedlings had the highest total amounts (microg). Compared with the control, sorgoleone content increased 6.1, 8.6, and 14.2 times when sorghum seeds were treated with auxins, Hoagland solution, and a combination of auxins and Hoagland solution, respectively. Among the innate immunity response elicitors, cellulose (an elicitor of plant origin) stimulated higher sorgoleone production than the others, and it produced 6.2 times more sorgoleone than the control. Combined treatment of sorghum seeds with half strength Hoagland solution and 5 microg ml(-1) of IBA significantly increased both root growth and sorgoleone content in sorghum seedlings.

To characterize the biochemical differences in paraquat-resistant and -susceptible biotypes of Erigeron canadensis L. collected from Korea, we investigated the constitutive levels of various antioxidants such as antioxidant enzymes and low molecular weight antioxidants in leaves, as well as after paraquat treatment. The activities of superoxide dismutase, peroxidase, ascorbate peroxidase, and catalase were higher in the paraquat-resistant biotype than in the paraquatsusceptible biotype. Reduced ascorbic acid content was higher in the resistant biotype, but the content of reduced glutathione was higher in the susceptible biotype. These results indicate that one of the paraquat-resistant mechanisms in E. canadensis in the present study might be related to protecting the activities of antioxidant enzymes, such as superoxide dismutase, peroxidase ascorbate peroxidase, and catalase, as well as the contents of low molecular weight antioxidants such as ascorbate and glutathione.

The hairy root of Fagopyrum tataricum (Tartary buckwheat) has been shown to produce allelochemicals that have herbicidal activity. The hairy root culture technique has been previously employed with F. tataricum to isolate several phenolic compounds. The purpose of this study was firstly to optimise the hairy root culture of F. tataricum using different growth media, supplemented with varying concentrations (0.1-1.0 mg L )1 ) of auxin, for phenolic compound production and secondly to evaluate the phenolic compounds for herbicidal activity to different weed species both in growth chamber and in glasshouse studies. The results suggest that hairy roots grown in half-strength Schenk and Hildebrandt medium showed the highest levels of growth (10.8 g L )1 ) and the maximal production of gallic acid, chlorogenic acid and rutin. Among the different auxin treatments, indole-3-butyric acid at 0.5 mg L )1 produced 24% more hairy root mass than the control. Hairy root extracts of F. tataricum suppressed germination and shoot and root growth in tested weeds, with the grass weed species showing greater susceptibility than the broad-leaved weed species in a growth chamber bioassay. In the glasshouse experiments, post-emergence application of the extract on 21-dayold seedlings had a greater inhibitory effect than the pre-emergence application of hairy root extract. Setaria viridis and Aeschynomene indica were the most susceptible species among grass and broad-leaved weed species, respectively. This study demonstrated that hairy root extract of F. tataricum contained allelopathic compounds and that their phytotoxicity varied with weed species.