Changes in haemolymph ion concentrations of Astacus astacus L. and Pacifastacus leniusculus (Dana) after exposure to low pH and aluminium

During exposure to soft water, acidified to pH 4.0, the haemolymph concentrations of Na⁺, K⁺, and Cl^– decreased whereas the Ca²⁺ concentration fluctuated in Astacus astacus. The haemocyte content of K⁺ decreased from 9% to 2% of the total haemolymph K⁺ content after exposure to pH 3.7 for 3 days. Within 14 days, 250 µg Al³⁺ l^–1, as Al₂(SO₄)₃ at pH 5.0, reduced the haemolymph Na⁺ content in Astacus astacus and Pacifastacus leniusculus, however, the effects were less pronounced than earlier reported for fish. Disturbed ion regulation, mainly depending on low pH, is thought to contribute to the absence of these species in acid waters.     

The effect of soil water status on critical phosphorus concentrations inStylosanthes hamata cv. Verano

Summary The effect of soil water status on the critical phosphorus concentration (CPC) determined in apices and whole tops ofStylosanthes hamata cv. Verano was investigated in a glasshouse trial. The species was grown with six rates of P and three ranges of soil water potential and was harvested at 10 and 14 weeks after germination. The CPC of both whole tops and apices decliced between the two harvests. At the first harvest the CPC of both whole tops and apices increased as the soil water potential decreased but at the second harvest there was no effect of soil water potential on CPC. It is suggested that at the earlier harvest water stress was delaying physiological development, resulting in a CPC characteristic of chronologically younger tissue, but that by the second harvest the decline in CPC with age had ceased for all water treatments.     

Change in floral nectar components from fresh to senescent flowers ofCapparis spinosa (Capparidaceae), a nocturnally flowering Mediterranean shrub

We studied the nectar characteristics in relation to flower age of the summer flowering Mediterranean shrubCapparis spinosa in three localities in Southern Greece. Anthesis was nocturnal. Nectar volume, concentration, and sucrose/hexose ratio varied with site, year, and between individual plants; amino acid concentration varied only with site. The sucrose/hexose ratio decreased considerably with flower age, while the glucose/fructose ratio remained constant (ca. 1), implying that nectar sucrose broke down in the course of anthesis. Sugar breakdown increased with water content of nectar. Amino acid concentration was strongly age-dependent: It was low in fresh flowers, relatively high in middle-aged ones (except aspartic acid that was extremely increased), and very high in senescent ones. We attribute the amino acid changes to phenomena related to flower senescence in the dark.     

In-vitro evaluation of the antimicrobial activity of Bauhinia variegata,locally known as koiralo

Bauhinia variegata, commonly known as Koiralo is considered as medicinal plant in Nepal and India. The alcoholic extract of this plant was found to have antimicrobial activity against Bacillus subtilis (ATCC 6635) Pseudomonas aeruginosa (ATCC 27853), Salmonella typhi, Shigella dysenteriae, Staphylococcus aureus (ATCC 29213) and Vibrio cholerae. The largest zone of inhibition (18 mm) was found to be exhibited against B. subtilis. For this organism the minimum bactericidal concentration (MBC) of the crude extract was 0.39 mg/ml. The extract was found to be more effective against gram-positive than gram-negative bacteria. The antimicrobial activity of the extract was found to be decreased during purification.     

The effect of nitrate concentration in a flowing solution system on growth and nitrate uptake of twoPlantago species

Summary Juvenile plants ofPlantago lanceolata andP. major ssp.major were grown in a flowing solution system at 7.5 mM or 9.5 M NO₃. The parameters investigated were: RGR, shoot weight percentage, leaf length, length of main root axis, shoot concentrations of major ions and organic N, and the specific uptake rate for NO₃. At 9.5 M NO₃ growth ofP. major was not hampered, whereas shoot growth and leaf length ofP. lanceolata were reduced. The NO₃ concentration ofP. lanceolata decreased more than that ofP. major. The different performances of the species at 9.5 M NO₃ were associated with different specific uptake rates. In both treatments the root system ofP. major was shorter than that ofP. lanceolata. P. lanceolata accumulated more NO₃ in the leaves. The performance of thePlantago species is discussed in relation to the availability of nutrients in their habitats.Grassland Species Research Group. Publication no. 37.     

Preparation and partial characterization of a Lactobacillus lactis bacteriophage

High-titer lysates of a bacteriophage active against Lactobacillus lactis were prepared from liquid cultures as well as from areas of confluent lysis in soft-agar overlayers. Phage concentration and purification were accomplished by means of polyethylene glycol precipitation, differential centrifugation, and cesium chloride gradient centrifugation. The buoyant density of this phagein cesium chloride was 1.4795 g/ml. Characterization of phage growth cycle by one-step growth experiments under optimal conditions showed that the latent period was about 120 min, that the rise period lasted approx. 130 min, and that the average burst-size was about 80.Abbreviations p.f.u. plaque forming units - m.o.i. multiplicity of infection - PEG polyethylene glycol - SSC standard saline citrate solution     

Acorn mast drives long-term dynamics of rodent and songbird populations

Resource pulses can have cascading effects on the dynamics of multiple trophic levels. Acorn mast is a pulsed resource in oak-dominated forests that has significant direct effects on acorn predators and indirect effects on their predators, prey, and pathogens. We evaluated changes in acorn mast, rodent abundance, raptor abundance, and reproductive success of a ground-nesting songbird over a 24-year period (1980–2004) in the southern Appalachian Mountains in an effort to determine the relationships among the four trophic levels. In particular, we examined the following: acorn mast from red oaks (Quercus rubra) and white oaks (Q. alba), abundance of white-footed mice (Peromyscus leucopus) and deer mice (P. maniculatus), population estimates of seven raptor species from three feeding guilds, and nest failure and number of juveniles of dark-eyed juncos (Junco hyemalis). Finally, we recorded seasonal temperature and precipitation to determine the effects of weather on each trophic level. We found that weather patterns had delayed effects of up to 3 years on these trophic interactions. Variation in acorn mast, the keystone resource in this community, was explained by weather conditions as far back as 2 years before the mast event. Acorn mast, in turn, was a strongly positive predictor of rodent abundance the following year, whereas spring and summer temperature and raptor abundance negatively affected rodent abundance. Dark-eyed junco nests were more likely to fail in years in which there were more rodents and raptors. Nest failure rate was a strong predictor of the number of juvenile juncos caught at the end of the summer. Our results improve our understanding of the complex ecological interactions in oak-dominated forests by illustrating the importance of abiotic and biotic factors at different trophic levels. Ethan D. Clotfelter and Amy B. Pedersen contributed equally to the writing of this paper.     

Influence of phosphate rock sources and rates on rice and common bean production in an Oxisol

A field experiment was conducted for five consecutive years to determine upland rice (Oryza sativa L.) and common bean (Phaseolus vulgaris L.) response to eight P sources at three P rates in an Oxisol of Central Brazil. The P sources tested were triple superphosphate (TSP), Arafertil phosphate partially acidulated (APPA), phosphate of Patos partially acidulated (PPPA), phosphate of Araxa concentrated (PAC), phosphate of Catalao (PC), phosphate of Jacupiranga (PJ), phosphate of Patos de Minas (PPM), and phosphate of Abaete (PA). All phosphate rock sources were of Brazilian origin. The P rates used were 87, 174 and 262 kg P ha^-1. Yield response to P sources and rates varied from crop to crop. Rice and bean yields were significantly correlated with Bray 1 P, but not Mehlich 1 P. In the first year, TSP and the two partially acidulated phosphate rocks (APPA, PPPA) produced higher grain yields. In the second year and all remaining years of the experiment, the efficiency of phosphate rock sources as measured by grain yield was equivalent to TSP or partially acidulated P sources. The results suggest that these phosphate rock sources could be used in rice-bean rotations on Brazilian Oxisols. Yield losses in the first year could be partially offset by the addition of a small amount of soluble P.     

Effect of CO2 enrichment and nitrogen availability on resource acquisition and resource allocation in a grass,Bromus mollis

Summary The effects of CO₂ enrichment on the growth, biomass partitioning, photosynthetic rates, and leaf nitrogen concentration of a grass, Bromus mollis (C₃), were investigated at a favorable and a low level of nitrogen availability. Despite increases in root: shoot ratios, leaf nitrogen concentrations were decreased under CO₂ enrichment at both nitrogen levels. For the low-nitrogen treatment, this resulted in lower photosynthetic rates measured at 650 l/l for the CO₂-enriched plants, compared to photosynthetic rates measured at 350 l/l for the non-enriched plants. At higher nitrogen availability, photosynthetic rates of plants grown and measured at 650 l/l were greater than photosynthetic rates of the non-enriched plants measured at 350 l/l. Water use efficiency, however, was increased in enriched plants at both nitrogen levels. CO₂ enrichment stimulated vegetative growth at both high and low nitrogen during most of the vegetative growth phase but, at the end of the experiment, total biomass of the high and low CO₂ treatments did not differ for plants grown at low nitrogen availability. While not statistically significant, CO₂ tended to stimulate seed production at high nitrogen and to decrease it at low nitrogen.