Hideo Kakuta

An allelopathic substance exuded from germinating watermelon seeds

When watermelon seeds were cultured in a Petri dish together with amaranth, barnyard grass, cockscomb, lettuce or tomato seeds, the shoot growth of amaranth and cockscomb was markedly promoted, whereas the shoot growth of lettuce and tomato was inhibited. The shoot growth of barnyard grass was not affected. These results suggest that plant-selective allelopathic substance(s) affecting the shoot growth of other plant seedlings were exuded from watermelon seeds. An allelopathic substance was isolated from the exudates of germinating watermelon seeds and identified as vanillic acid by its spectral analysis and Rf value on TLC. Vanillic acid promoted the shoot growth of cockscomb at the concentrations of 300 to 10 mg/l and that of amaranth at the concentrations of 30 to 3 mg/l, although the shoot growth of amaranth was inhibited by 300 mg/l of vanillic acid. The shoot growth of lettuce and tomato was inhibited at the concentrations higher than 30 mg/l by vanillic acid. However, the shoot growth of barnyard grass was not affected at the concentrations used. All these results suggest that vanillic acid may play as a major component of allelopathic substance(s), which shows plant-selective activity, in the exudates of germinating watermelon seeds.

Light-induced auxin-inhibiting substance from sunflower seedlings

Abstract A plant growth-inhibiting substance was isolated from de-etiolated sunflower ( Helianthus annuus ) seedlings. Its structure was identified as 8-epixanthatin from IR, 1 H NMR and EI mass spectra. 8-Epixanthatin was detected in sunflower and burweed shoots, but not in lettuce, radish, oat and corn. 8-Epixanthatin inhibited auxin-induced growth of sunflower hypocotyl and oat coleoptile sections at concentrations higher than 100 μM and 30 μM, respectively, and the elongation of cress roots at concentrations higher than 30 μM. However, it did not affect gibberellin-induced growth of lettuce hypocotyls and second leaf sheaths of rice at the various concentrations used. The light-grown seedlings were observed to contain a higher level of 8-epixanthatin than the dark control, and the difference in its level was noticeable before the growth inhibition by light appeared. These results suggest that 8-epixanthatin with its auxin-inhibiting activity might contribute to the light-induced growth inhibition of sunflower seedlings.

Synthesis and absolute configuration of lepidimoide, a high potent allelopathic substance from mucilage of germinated cress seeds

Abstract Lepidimoide (1), 1,2-cis-linked disaccharide, was synthesized from D-glucose and α-L-rhamnose for determination of the absolute configuration.

Phytotoxicity and fate of 1,1,2-trichloroethylene: a laboratory study.

Abstract1,1,2-Trichloroethylene (TCE), a chlorinated organic contaminant, poses serious environmental concerns. A study was conducted to evaluate the phytotoxicity of TCE to a crop species and its fate in vermiculite. Growth bioassays were carried out using carrot (Daucus carota L.) as the test species. Three different concentrations, 0.25, 0.50, and 1 ppm were used to evaluate phytotoxicity of TCE. When added to petri plates with cotton pads, TCE did not have any effect on carrot seedling growth. However, when added to vermiculite, it significantly suppressed growth. Shoot growth was inhibited only at the 1 ppm concentration. Recovery experiments were carried out to study the fate of TCE in vermiculite. A significant decline in the percent recovery was observed with time. Interestingly, TCE additional peaks (unknown organic molecules) were detected with declining concentrations. The available chloride ion concentration in vermiculite containing 1 ppm of TCE for 24 hr was significantly higher compared to control.