A Multi-Unit Sampling System and Its Use in the Characterization of Ultradian and Infradian Growth in Tetrahymena*

SYNOPSIS. A multi-unit automatic sampling device for investigation of microbial growth under a wide variety of conditions is described. The kinetics of asynchronous population growth for batch cultures of Tetrahymena pyriformis (W) at several temperatures show that there are 2 distinct growth phases: an exponential ultradian growth phase that is strongly temperature dependent and a non-stationary growth phase, the infradian phase, that shows little or no temperature dependence over the range from 15–27 C.     

The Effect of Vitamin A on Cellular Differentiation and Mucous Glycoprotein Synthesis in Long-Term Rat Tracheal Organ Cultures

Rat tracheal explants maintained as organ cultures exhibited a normal mucociliary epithelium for at least 46 days in the presence of retinyl acetate. In the absence of vitamin A the explant epithelium became quiescent or underwent a metaplastic change to a keratinizing squamous epithelium. This process was accelerated if explants were derived from vitamin A-deficient animals. Autoradiographic examination showed that [³H]glucosamine label accumulated in various cell types in the explant, but especially in the epithelium. It was found that the explants secreted mucous glycoproteins into the medium and that the production and biochemical characteristics of a specific mucin fraction were dependent upon the vitamin A status of the explant.     

Flag Leaf Anatomy of Triticum and Aegilops Species in Relation to Photosynthetic Rate

Quantitative anatomical and other measurements were made onfully expanded flag leaves of a series of diploid, tetraploidand hexaploid Triticum and Aegilops species, and photosyntheticrates per unit leaf area were measured at light saturation (P_max). Diploids had the highest P_max, hexaploids the lowest with tetraploidsbeing intermediate. The anatomical features of tetraploids andhexaploids were generally similar, but different from the diploids.The diploids had thinner leaves with less dry matter and chlorophyllper unit area. The surface area of the mesophyll cells per unitvolume of mesophyll tissue was similar for all ploidy levels,as was the ratio mesophyil cell surface area per unit leaf area.It is argued that while these anatomical features are unlikelyto account for the observed variation in Pmax, it is possiblethat other structural factors with which they are correlatedmay causally influence P_max. One such feature is the averagediffusion path length from the plasmalemma at the cell surfaceto the sites of carboxylation. Anatomy, photosynthesis, mesophyll, cell size, Triticum, Aegilops, polyploidy     

Effects of some systemic imidazole and triazole fungicides on white clover and symbiotic nitrogen fixation by Rhizobium trifolii

Effects of prochloraz, imazalil, diclobutrazol, triadimefon and propiconazole were studied. Compared with most systemic fungicides previously tested they were all relatively toxic to R. trifolii on agar. Effects of soil residues of the compounds on the growth and nitrogen fixing capacity of white clover were measured. The lowest concentration of the fungicides used was that which would be present if all the active ingredient from a single application remained unchanged and evenly distributed in the top 5 cm of soil. This concentration of diclobutrazol decreased the size and weight of 11-wk-old clover plants. The rate of nitrogen fixation was reduced by twice this concentration and root nodulation by four times this amount. None of the other fungicides had any significant effect. The possibility of field application of diclobutrazol to cereals causing damage to clover crops is discussed. It is questionable whether harmful soil residues will ever accumulate from normal usage of the fungicide but exceeding the recommended rate of application, or application to cereals undersown with clover, might cause undesirable effects on the clover.     

Seed treatments with benomyl and other fungicides for the control of Ascochyta pisi on peas

In three experiments, using laboratory, glasshouse and field tests, seed dressings of benomyl-1½ (42.4 g) to 2 oz (56.6 g) Benlate 50% w.p. per 28 lb (12.7 kg) of seed-gave complete control of Ascochyta infection of pea seeds. Mixtures of benomyl and captan and benomyl and thiram were also effective. Carboxin, captan, and thiram used as seed dressings, either singly or in mixtures, did not eliminate the pathogen from peas. Germination, emergence and seedling vigour were not impaired by any dressing.     

Characterization of polymorphic microsatellite loci for the polychaete tubeworm Hobsonia florida

Eight dinucleotide microsatellite loci were isolated and characterized from Hobsonia florida, a tube‐dwelling ampharetid polychaete. The identified loci were highly polymorphic, with allelic diversity ranging from six to 11 alleles. Levels of expected heterozygosity were 0.52 or greater in all cases, averaging 0.78 across the complete set of loci. Cross‐species amplification was successful in three of the eight loci for one or both of the other species (Melinna cristata and Ampharete acutifrons) tested. Although these novel loci were designed for immediate utility in H. florida population‐level research, these results indicate they may prove useful in studies of other related taxa.