The growth, yield and nutrient uptake of winter wheat following root-pruning

The effect of root-pruning on shoot growth was investigated in winter wheat growing in lysimeters. Removal of half of the root axes at the beginning of stem elongation reduced shoot dry matter, determined 1 month after pruning, by 13% and grain yield by 8%. Removal of either the seminal or nodal root system during tillering reduced shoot dry weight, measured during the growing season, by 7% and grain yield by 25%. Root-pruning had negligible, or only transient, effects on the concentration of nitrogen, phosphorus, potassium, magnesium and manganese in the shoots. The harvest index was not affected by root-pruning.     

Successional Sequences of Microbial Colonization on Three Species of Rhodophycean Macroalgae

The successional sequences of microbial colonization of Centrocerasclavulatum, Bryocladia cuspidata, and Gelidium crinale wereobserved by SEM. Colonization was initiated by filamentous andsmaller rod or coccoid bacteria, and these microbes were replacedby diatom populations in a successional pattern on Centrocerasand Bryocladia. Gelidium was colonized primarily by bacteria.The spatial fouling patterns on each host plant could be correlatedwith plant shape. Differences in epiphyte attachment morphologiescould be correlated in some species with the host plant or withthe position of the epiphyte on the host plant. Diatoms, epiphytes, fouling, microbial colonization, periphyton     

Pathogenic variability of downy mildew (Sclerospora graminicola) on pearl millet. I. Host cultivar reactions to infection by different pathogen isolates

Cultivars of pearl millet were challenged by isolates of downy mildew collected from various locations in West Africa and India in order to ascertain whether variability in cultivar response was genetically or environmentally determined. Results of experiments, in Polythene tunnels which imitated tropical field conditions, were confirmed by more precise experiments in an isolation plant propagator. The most important conclusion was that variation is determined by host and pathogen genotypes. West African isolates of the pathogen were generally more pathogenic than Indian isolates. However, there were also substantial differences between two isolates collected from different host cultivars at the same location in Upper Volta. Cultivar ICH105 differentiated between West African and Indian isolates. Cultivars 700516 and MBH110 also showed differential responses between isolates. In contrast two distinct types of symptom expression were recorded and found to be characteristic of cultivar genotype, independent of pathogen isolate. The possibility that both race specific and race non-specific resistance may coexist in this little understood pathosystem is discussed and the practical implications are considered.     

Phytosterols and Other Lipids as Survival Factors for Tetrahymena at 0–5 C

SYNOPSIS. Tetrahymena pyriformis syngen 1, mating type II, (optimal growth temperature ∼ 37 C) ordinarily dies out in 5-14 days at 0-5 C. Dying cells were lumpy, suggesting membrane damage. By supplying crude soy lecithin, survival at 0-5 C was prolonged (after growth in peptone-yeast-dextrin) to at least 22 weeks. Crude soy sterols or sitosterol or stigmasterol, and antioxidant, e.g., Ionox 330 or ascorbylpalmitate, permitted survival of cells in suspension or in growth media for at least 16-22 weeks. These sterols are known to protect against triparanol toxicity, which suggested that triparanol, which blocks cholesterol synthesis in higher animals, might enhance cold-induced injury. Triparanol was more toxic at 0–5 than at 28 C for cell suspensions and cells in growth medium; this toxicity was annulled by crude soy lecithin or β-sitosterol, the only phytosterol tested. The synthetic medium intended as a control on the crude media became toxic at 0–5 C. Protection against cold damage is discussed as a means of elucidating the role of sterols—especially phytosterols—and other lipids in maintaining the integrity of the ciliate cell membrane.     

Physical and Serologic Properties of an Antigen Prepared from Erythrocytes of Horses with Acute Babesiosis*

SYNOPSIS. By means of precipitation with protamine sulfate, a soluble antigen (PS) was obtained from erythrocytes of horses with acute babesiosis due to Babesia caballi and B. equi. This antigen reacted in gel diffusion tests with sera from horses recovered from acute babesiosis. The PS antigen was found to be muco-protein, susceptible to destruction by trypsin and taka-diastase. Analysis of the antigen by paper electrophoresis revealed 2 components which were not present in similar preparations made from erythrocytes of Babesia-free horses. When the PS antigen was heated in boiling water for 30 minutes, a serologically inactive precipitate was formed; however, the supernate remained serologically active and was termed boiled PS (BPS) antigen. This antigen was polysaccharide in nature; its serologic activity was destroyed by taka-diastase. In gel diffusion tests with sera of recovered horses, the PS antigen formed 2 lines of precipitation which coalesced in a single line formed between these sera and the BPS antigen. Both PS and BPS antigens reacted with sera of horses recovered from acute babesiosis in the gel-diffusion test, but not with sera of dogs and rats recovered from acute infection with Babesia canis and Babesia rodhaini, respectively. The serologic specificity of these antigens suggests that they might have application in the serodiagnosis of inapparent Babesia infections of equine animals.     

Evidence for a Calcium/Calmodulin Involvement in Density-Dependent Melanogenesis in Murine B16 Melanoma Cells

Previous work from our laboratory has shown that both cyclic AMP and calcium/calmodulin appear to be involved in the regulation of melanogenesis in murine B16 melanoma cells. In these cells as in murine Cloudman S91 cells, melanogenic responsiveness to melanocyte-stimulating hormone (MSH) varies with cell density in culture. Our objective in this study was to learn more about the intracellular systems involved in the control of melanogenesis, particularly the role played by calcium. The melanogenic response to αMSH was compared to the response to drugs affecting intracellular free calcium and calmodulin over a range of cell densities in B16F1 cells. αMSH-stimulated melanin production was extremely density-dependent but αMSH-stimulated cyclic AMP production was independent of cell density. The melanogenic response to agents that increased intracellular calcium (A23187) or inhibited intracellular calmodulin varied with cell density. A drug (TMB8) that lowered intracellular free calcium, however, increased melanogenesis independently of cell density. At high cell density it was found that an elevation in calcium decreased melanogenesis, whereas agents that reduced calcium or inhibited calmodulin activity increased melanogenesis. At low cell density, however, the inhibitory response to A23187 was lost and in some experiments even stimulated melanogenesis. These data suggest that the calcium/calmodulin signalling system has an inhibitory influence on melanogenesis, and its expression, which depends upon cell density, may also modulate the response to stimulatory agents such as αMSH.     

Wintering site fidelity and movement patterns of Western Sandpipers Calidris mauri in the San Francisco Bay estuary

Western Sandpipers Calidris mauri are the most numerous shorebird species in the San Francisco Bay estuary during winter. A sample of 106 Western Sandpipers was captured in mist nets and radio-marked with 1-g transmitters to examine their wintering site fidelity and movements. Differences in distances moved, home range extent and core area size were examined by age, sex, season, site, time of day and tide. All birds remained in the south San Francisco Bay region during winter and exhibited strong site fidelity, with a mean home range of 22.0 km² or only 8% of the study area. First-year birds had larger home ranges (26.6 ± 3.6 km²) than adults (17.2 ± 2.5 km²) in winter, but home range sizes of males and females were not significantly different in any period. Home range sizes were similar between seasons, but core areas were smaller in spring (6.3 ± 1.2 km²) than in early (9.6 ± 4.0 km²) or late (11.6 ± 1.6 km²) winter. Movements and home range size were similar for radio-marked birds located during day and night. The high degree of regional and local site fidelity demonstrated that the mixture of natural mud fiats and artificial salt ponds in southern San Francisco Bay provided sufficient resources for large wintering populations of Western Sandpipers.     

Efficiency of Selenite Cystine and TT Enrichment Broths for the Detection of Salmonella

Comparisons of selenite cystine (SC) and TT enrichment broths for detecting salmonellas were made with pure culture suspensions, with samples of naturally or artificially contaminated foods and with poultry feed. Selenite cystine recovered higher numbers of salmonellas from pure cultures and ground beef, while TT broth recovered higher numbers from pork sausage and poultry feed. Differences in the recovery of salmonellas from other food products appeared to be insignificant. The use of both SC and TT is thus recommended for maximal recovery of these organisms.