No abstract

The effects of several inorganic elements contained in B5 medium on Phytophthora stem rot disease reduction of Glycine max (L.) Merr. cv. Chusei-Hikarikuro, fungal growth of Phytophthora sojae isolate and zoospore release were investigated. Application of B5 solution and macro inorganic nutrients in the B5 medium prior to inoculation significantly inhibited infection, compared with controls. Various concentrations of KNO 3 , (NH 4 ) 2 SO 4 , MgSO 4 , CaCl 2 and NaH 2 PO 4 in the presence of macro inorganic nutrients were investigated in an effort to determine the elements most effective in suppressing the incidence of disease. A concentration of 2.47-24.7 mm KNO 3 and 0.1-10.2 mm CaCl 2 greatly inhibited infection. Although mycelium growth of the isolate was affected by the potassium and calcium concentration, no significant relationship was observed between inhibition of the growth rate and disease reduction at 2.47 mm KNO 3 and 0.1-5.1 mm CaCl 2 application. Disease suppression recorded in laboratory experiments using pathogen mycelium was due to the response of plant tissues rather than a direct inhibition of pathogen fungal growth by the application of potassium or calcium. The extent of disease reduction was related to an increased potassium and calcium uptake by plants, suggesting that the effective elements in reducing Phytophthora stem rot were potassium and calcium. The presence of 2.47-247 mm KNO 3 and 5.1-10.2 mm CaCl 2 decreased the release of zoospores, although 0.1-2.5 mm CaCl 2 significantly induced zoospore release. These results suggest that applying a solution containing more than 2.47 mm of potassium and 5.1 mm of calcium can decrease the incidence of disease in agricultural fields by the inhibition of zoospore release.

No abstract

No abstract

Limnological surveys were undertaken on a small coastal lake on Kamikoshiki Island , Lake Kaiike (surface area: 0.15 km2; maximum depth: 11.6 m). The lake and adjacent Lake, Namakoike (surface area: 0.50 km2; maximum depth: 24.4 m), are separated from the sea by narrow gravel bars. Lake Namakoike has a considerable exchange of water with the sea, because a part of the gravel bar has been worn away by wave action and through it sea water seeps freely into the lake or lake water into sea following the tidal cycle of sea level. Usually, water flows through a small ditch from Lake Kaiike into Lake Namakoike. But an reverse flow occurs intermittently on a rare occasion when tidal action becomes great enough to raise the lake level of Namakoike higher than that of Kaiike. Chlorinity of lake water of Namakoike ranges between 13-17 %o. Chlorinity of surface water of Lake Kaiike is 7-9 %o, and it increases downwards and attains 18.64 %o near the bottom. The deeper high saline water of Lake Kaiike originates in sea water which seeps through the gravel bar between the lake and sea. Unusually high temperature and dissolved oxygen maxima are observed in the middle. layer, where the vertical gradient of chlorinity is the highest (halocline). Dissolved oxygen has been depleted in the deeper water and hydrogen sulfide is present.