Distribution of Zearalenone-Producing Fusarium Species in Japan

One hundred sixty-six isolates of Fusarium spp. from domestic cereal grains, feed, and other sources were examined for their ability to produce zearalenone on autoclaved moist rice grains. They belonged to the following species (number of producers/number tested): F. roseum (9/28), F. roseum (Culmorum) (3/4), F. roseum (Gibbosum) (2/5), F. roseum (Avenaceum) (1/2), F. roseum (Scirpi) (0/1), F. tricinctum (1/4), F. tricinctum (Sporotrichiella) (0/7), F. lateritium (1/1), F. episphaeria (0/2), F. moniliforme (0/3), F. oxysporum (0/12), F. rigidiusculum (0/4), F. solani (0/4), F. splendens (0/1), F. nivale (0/2), and Fusarium spp. (15/86). Zearalenone was isolated from molded rice by ethanol extraction and purified by column chromatography. Selected isolates of F. roseum M-3-2 and F. roseum (Gibbosum) A-O-2 produced 50 to 100 mg of zearalenone per kg of rice. Increased yields (250 to 407 mg/kg of rice) were obtained by F. roseum M-3-2 when the substrate was supplemented with 1% peptone.     

Production of l-Arginine by Arginine Hydroxamate-Resistant Mutants of Bacillus subtilis

l-Arginine hydroxamate inhibited the growth of various bacteria, and the inhibition was readily reversed by arginine. l-Arginine hydroxamate (10(-3)m) completely inhibited the growth of Bacillus subtilis. This inhibitory effect was prevented by 2.5 x 10(-4)ml-arginine, which was the most effective of all the natural amino acids in reversing the inhibition. l-Arginine hydroxamate-resistant mutants of Bacillus subtilis were isolated and found to excrete l-arginine in relatively high yields. One of the mutants, strain AHr-5, produced 4.5 mg of l-arginine per ml in shaken culture in 3 days.     

Dark transformations of phytochrome in cotyledons of Pharbitis nil

Pharbitis seedlings grown in total darkness or continuous far-redirradiation were exposed to 30 min of red irradiation followedby a dark period, and in vivo phytochrome in their cotyledonswas photometrically assayed at various times. Loss of photo-reversibilityof P_fr after the exposure to red light occurred without darkreversion to P_r in cotyledons of both seedlings. P_fr decay inthe former cotyledons was mostly prevented in the first 30 minunder red light illumination, while that in the latter occurredwithout such a lag phase. P_fr was no longer photometricallydetectable by the eighth hr after irradiation at both 18?C and25?C. No evidence has yet been obtained to show a correlation betweenphotometrically detectable phytochrome in vivo and the red far-redreversible responses of flowering. (Received August 6, 1974; )     

Phytochrome action in Oryza sativa L. VII. Effects of light and aeration on coleoptile growth under submerged conditions

Coleoptile growth of intact rice seedlings under submerged conditionswas not much affected by the continuous irradiation of red light.But, if aerated, growth was strongly inhibited by a low-energybrief irradiation of red light, and this red light-induced effectwas reversed by a brief exposure to far-red light. The responsesto red and far-red light were repeatedly reversible. The amountof photometrically detectable phytochrome in non-aerated coleoptiletissues was found to be as low as one third that in aeratedones. After the conversion of Pr to Pfr by a brief red irradiation,the total (A) of the aerated tissues decreased to about onefifth that of the original level within 6 hr at 24?C, whilethe Pfr in the non-aerated tissues was significantly less decayed. ¹Present address: The Ocean Research Institute, University ofTokyo, Nakano, Tokyo 164, Japan. (Received April 30, 1974; )     

Biological and Chemical Detection of Trichothecene Mycotoxins of Fusarium Species

The procedure for biological and chemical detection of trichothecene-type mycotoxins and its application to the screening of Fusarium for toxic strains were described.     

Production of the Hepatotoxic Chlorine-Containing Peptide by Penicillium islandicum Sopp

Twenty-six strains of Penicillium islandicum Sopp were tested for production of a chlorine-containing peptide (Cl-peptide), which is a hepatotoxin. Highest levels of the mycotoxin were produced in a modification of Wickerham medium. The mycotoxin was isolated by adsorption on charcoal and, after washing the charcoal with acetone-water (1:1), was eluted into n-butanol. Further purification was accomplished by gel filtration. Maximum yields were 10 to 20 mg of toxin per liter of culture filtrate.     

Sensitivity analysis of ecosystem CO<Subscript>2</Subscript> exchange to climate change in High Arctic tundra using an ecological process-based model

Arctic terrestrial ecosystems are extremely vulnerable to climate change. A major concern is how the carbon balance of these ecosystems will respond to climate change. In this study, we constructed a simple ecological process-based model to assess how the carbon balance will be altered by ongoing climate change in High Arctic tundra ecosystems using in situ observations of carbon cycle processes. In particular, we simulated stand-level photosynthesis, root respiration, heterotrophic respiration, and hence net ecosystem production (NEP) of a plant community dominated by vascular plants and mosses. Analyses were carried out for current and future temperature and precipitation conditions. Our results showed that the tundra ecosystem was a CO₂ sink (NEP of 2.3–18.9 gC m^?2 growing season^?1) under present temperature conditions. Under rising temperature (2–6 °C), carbon gain is significantly reduced, but a few days’ extension of the foliage period caused by their higher temperatures compensated for the negative effect of temperature on NEP. Precipitation is the major environmental factor driving photosynthetic productivity of mosses, but it had a minor influence on community-level NEP. However, NEP decreased by a maximum 15.3 gC m^?2 growing season^?1 under a 30-day prolongation of the moss-growing season, suggesting that growing season extension had a negative effect on ecosystem carbon gain, because of poorer light conditions in autumn. Because the growing season creates a weak CO₂ sink at present, lengthening of the snow-free season coupled with rising temperature could seriously affect the future carbon balance of this Arctic tundra ecosystem.