ANTIBIOTIC XG AS A SEED TREATMENT FOR THE CONTROL OF LEAF AND POD SPOT OF PEAS CAUSED BY ASCOCHYTA PISI

Antibiotic XG has been studied for its possible application as a pea seed treatment in the control of Ascochyta leaf and pod spot. Fungistatic properties of Antibiotic XG against Ascochyta Pisi at various concentrations in relation to pH and temperature in vitro were studied. At antibiotic concentrations up to 1 p.p.m. no fungistatic effect was observed at pH values from 3.5 to 6.5, but, at concentrations above 1 p.p.m., complete inhibition of growth was found at all pH values tested. In the temperature range of 22 °C. to 30 °C. antibiotic concentrations of 1 p.p.m. had no effect on growth. Fungicidal activity to spores of A. Pisi has also been tested. A spore suspension of 10,000 spores per ml. required an exposure of 12 hr. with an antibiotic concentration of 100 p.p.m. for complete lethal dosage. The soaking of diseased pea seed samples in Antibiotic XG at a concentration of 25 p.p.m. for a period of 18 hr. effectively controls A. Pisi infection as determined by laboratory test and does not seriously impair germination. This treatment is compatible with Spergon applied after the seed has been air-dried. Storage of treated seed for a period of three months did not affect the degree of control but reduced the germinative capacity in laboratory plate tests.

THE BLACK ROOTROT DISEASE OF TOBACCO.: II. PHYSIOLOGIC SPECIALIZATION OF THIELAVIOPSIS BASICOLA ON NICOTIANA TABACUM

Thielaviopsis basicola (Berk. & Br.) Ferraris exists in nature in two distinct forms, termed the brown and the gray wild type, which are differentiated on potato dextrose agar. Pathogenicity on tobacco was found to be a function of the wild type culture used. All gray wild type cultures were less pathogenic than the brown. The brown wild type cultures consisted of at least two physiologic races. Race I is found in the "old belt" of Ontario, and in Quebec, Ohio, and Connecticut. Race II is present in the "new belt" of Ontario and in Kentucky. Race II and all gray wild type cultures are less pathogenic than Race I. All cultural mutants were less pathogenic than wild type cultures.

THE PROTEOLYTIC ENZYMES OF MICROORGANISMS: III. SOME CHARACTERISTICS OF EXTRACELLULAR PROTEASES PRODUCED IN SUBMERGED CULTURE

Some of the general characteristics of the proteases liberated into the culture medium by molds and actinomycetes grown in submerged culture have been studied. Species of Alternaria, Streptomyces, Mortierella, and Gliocladium were used. The enzymes resemble trypsin in that they are most active at a pH slightly above 7 and are inhibited by a preparation of egg albumin. They are stable at low temperatures but suffer marked losses in activity when stored for 16 hr. above 40 °C. The most rapid hydrolysis of gelatin occurs at temperatures between 40 °C. and 50 °C. The enzymes from different organisms show definite differences with respect to their ability to attack different proteins, gelatin and casein being in general the most readily digested. The protease systems from different organisms also vary with respect to the extent to which they can digest gelatin; some enzymes are able to release about three times as many amino groups from gelatin as others. The limit of the hydrolysis is not dependent upon substrate concentration but is slightly affected by the concentration of enzyme. The enzymes were effective in liberating free amino acids from gelatin.

QUALITATIVE AND QUANTITATIVE DETERMINATION OF THE WHEAT LEAF CARBOHYDRATES

The nonreducing sugar in wheat leaves is probably entirely sucrose. It is the only abundant sugar. Free reducing sugars are absent, or almost absent from wheat leaves grown under the conditions described. The reducing power in the cleared alcoholic extracts of the leaves is, at least, partly due to degradation products of ascorbic acid. Other nonsugar reducing substances also are apparently present. The alcohol insoluble residue from wheat leaves contains little or no fructosan, dextrin, or starch at the two and one-half week old stage. Satisfactory methods for extracting and determining the sucrose are described. The following methods gave satisfactory results with wheat leaf extracts: the reducing power methods of Hanes and Somogyi after acid or preferably invertase hydrolysis, Ost's solution for fructose residues, the method of Neuberg and Strauss, the colorimetric resorcinol method. The latter method gives only approximate values for fructose residues unless the sugar concentration is high; the method is then fairly reliable. The following methods did not give satisfactory results: Hanes and Somogyi methods for free reducing sugars initially present in the extract, the hypoiodite titration for aldose sugars, and Sieben's method for fructose determination.

VOLUMETRIC DETERMINATION OF SMALL AMOUNTS OF IRIDIUM

A volumetric procedure is described for determining small amounts of iridium (from 2 to 20 mgm.). A solution of the metal is heated to dense fumes with sulphuric acid, cooled, diluted with water, and then oxidized with an excess of cerium (IV) sulphate solution. The resultant solution is titrated with a standard 0.01 N iron (II) sulphate solution, the course of the titration being followed potentiometrically. In solutions containing other platinum metals it has been found possible to determine iridium directly in some cases by this procedure; in other cases it was found necessary to remove osmium as the volatile tetroxide prior to oxidizing with cerium (IV) sulphate. The method is probably less accurate than existing gravimetric procedures, but offers considerable advantage in simplicity.

INTERRELATIONS OF DAILY METABOLIC CYCLE, ACTIVITY, AND ENVIRONMENTAL TEMPERATURE OF MICE

The daily metabolic cycle of fully fed, adult white mice, at temperatures from − 8 °C. to 37 °C., averaged 48 ml. of oxygen per mouse per hour between the highest nocturnal and lowest diurnal values, but this value was significantly greater at the higher temperatures. Over the same temperature range, forced activity of mice in a rotating metabolism chamber, up to approximately one-half the maximum running speeds studied, resulted in direct superimposition of work metabolism upon that of rest, with a constant metabolic increment at all temperatures. At the maximum running speeds the metabolism produced by the work decreased with decreasing temperature, with some gain in efficiency. The daily metabolic cycle fell within the activity range in which a given degree of work produced the same increment in oxygen consumption at all temperatures. These studies lead to the hypothesis that, in mice, some of the metabolic components of the daily cycle are additive over the biokinetic range. This results in a very large energy expenditure at low temperatures.

DEMONSTRATION OF AGGLUTININS FIVE HOURS AFTER INTRAPERITONEAL INJECTION OF PNEUMOCOCCUS TYPE I IN GUINEA PIGS

The inoculation of guinea pigs with pneumococci Type I intraperitoneally resulted in the development of homologous agglutinating antibodies, which were detected in the sera as early as five hours after inoculation. The early appearance of active immunity, and the attainment of a sufficient titer, would appear to govern survival to a fatal homologous re-infecting dose of the organism.

A STUDY OF THE ANTIBIOTIC ACTIVITY OF ACTINOMYCETES FROM SOILS OF NORTHERN CANADA

Of 660 cultures of actinomycetes isolated on a nonselective basis from soils from five locations in Northern Canada, 404 strains, or 61.2%, showed antagonism against at least one of eight test organisms consisting of five bacteria and three plant pathogenic fungi. The degree of activity ranged from slight to strong, with the number of test organisms inhibited by any single culture varying from one to six. In all, 49 different antibiotic spectra were observed. Activity against one or more of the pathogenic fungi was shown by 138 cultures, 20.9% of the isolates. The percentage of active cultures was greater, and the degree of inhibition much more marked, against Helminthosporium sativum than against Fusarium culmorum or Fusarium lini. The percentage of active isolates varied with the location and with the depth of the soil. It is suggested that the high proportion of actinomycetes with antagonistic properties occurring in northern soils may be related to the lower degree of plant development in such regions.

USE OF LIQUID AMMONIA IN THE FRACTIONATION OF WHEAT STRAW HOLOCELLULOSE

Wheat straw holocellulose, after soaking in liquid ammonia for 36 hr. at room temperature, was fractionated by successive extractions with cold water, 0.5% sodium carbonate, 0.5% potassium hydroxide, and 2.2% potassium hydroxide. Pretreatment with liquid ammonia increased the material soluble in cold water from 3% to 20.2%. Hemicellulose fractions were precipitated from the extracts by ethanol. A complete analytical balance was obtained by estimating ash, pentosan, uronic acid anhydride, acetyl, and methoxyl contents of the original holocellulose, of each of the fractions and of the residue. Analyses of the isolated fractions showed some systematic differences, with pentosan contents increasing and uronic acid anhydride decreasing progressively in the alkali soluble fractions. D-xylose, L-arabinose, D-glucose, D-galactose, and hexuronic acid in approximate molar ratios of 40:7:2:1:4 were found in the hemicellulose fractions. The presence of the sugars was confirmed by isolation of crystalline derivatives. A uronic acid complex, resistant to hydrolysis, was isolated and the components shown to be D-xylose and a monomethoxyl galacturonic acid.

NITROGEN DETERMINATION IN WHEAT LEAVES

A survey of the more promising modifications of the Kjeldahl method for nitrogen determination indicates that the method using mercuric oxide as the catalyst as recommended by the Association of Official Agricultural Chemists is the most satisfactory. However small discrepancies were found when this method was applied to wheat leaves fractionated into soluble and protein (actually coagulable and indiffusible) nitrogen fractions. This method includes all the nitrate nitrogen in wheat leaves together with the organic nitrogen even when no pretreatment with salicylic acid is used. A simple and satisfactory method of separating coagulable and indiffusible nitrogen from soluble nitrogen in wheat leaves and seedlings is described.