Takaaki Ishii

Growth stimulatory substances for vesicular-arbuscular mycorrhizal fungi in Bahia grass (Paspalum notatum Flügge.) roots

Three kinds of the growth stimulatory substances for vesicular-arbuscular mycorrhizal (VAM) fungi were isolated from the 25% methyl alcohol (MeOH) eluates of Bahia grass roots fractionated by flash chromatography. One of them was identified as eupalitin (3,5-dihydroxy-6,7-dimethoxy-4’-hydroxy flavone). At 10 ppm, this compound significantly stimulated the in vitro hyphal growth of a VAM fungus, Gigaspora ramisporophora Spain. The others were not identified. These results suggest that the flavonoids such as eupalitin, and the unidentified compounds may act as signal molecules in VAM symbiosis.

Continuous measurement of oxygen concentration in citrus soil by means of a waterproof zirconia oxygen sensor

A limiting-current type of zirconia oxygen sensor has been developed and its efficiency was tested for the determination of oxygen in soil air. This oxygen sensor is waterproof and has a very short response time. By the use of the sensor, changes in soil oxygen concentration, due to undecomposed organic material and waterlogging, were observed. The sensor was found to be highly stable in the soil and suitable for continuous oxygen monitoring in the field.