Growth and nitrogen fixation of legumes at increased salinity under field conditions: implications for the use of green manures in saline environments.

The use of legumes as green manure can potentially increase crop productivity in saline environments and thus contribute to the sustainability of agricultural systems. Here, we present results from a field experiment conducted in the Netherlands that addressed the efficiency of nitrogen (N) fixation by a legume at varying salinities. We grew Melilotus officinalis in an agricultural field using drip irrigation with water salinity varying in electrical conductivity between 1.7 and 20 dS m(-1). In the experiment, nearly 100 % of total plant N in M. officinalis was derived from symbiotic fixation at all but the highest salinity level (20 dS m(-1)). Our results indicated that this species derived substantial amounts of N via symbiotic fixation, the N becoming available in the soil (and thus available to crops) when cultivated legumes senesce and decompose. Based on the growth performance of M. officinalis and its ability to fix N at moderate soil salinity in our field experiments, we identified this species as a promising source for green manure in saline agriculture in temperate regions.

Ecophysiological response of Crambe maritima to airborne and soil-borne salinity.

BACKGROUND AND AIMS: There is a need to evaluate the salt tolerance of plant species that can be cultivated as crops under saline conditions. Crambe maritima is a coastal plant, usually occurring on the driftline, with potential use as a vegetable crop. The aim of this experiment was to determine the growth response of Crambe maritima to various levels of airborne and soil-borne salinity and the ecophysiological mechanisms underlying these responses. METHODS: In the greenhouse, plants were exposed to salt spray (400 mM NaCl) as well as to various levels of root-zone salinity (RZS) of 0, 50, 100, 200 and 300 mM NaCl during 40 d. The salt tolerance of Crambe maritima was assessed by the relative growth rate (RGR) and its components. To study possible salinity effects on the tissue and cellular level, the leaf succulence, tissue Na(+) concentrations, Na(+) : K(+) ratio, net K(+)/Na(+) selectivity, N, P, K(+), Ca(2+), Mg(2+), proline, soluble sugar concentrations, osmotic potential, total phenolics and antioxidant capacity were measured. KEY RESULTS: Salt spray did not affect the RGR of Crambe maritima. However, leaf thickness and leaf succulence increased with salt spray. Root zone salinities up to 100 mM NaCl did not affect growth. However, at 200 mM NaCl RZS the RGR was reduced by 41 % compared with the control and by 56 % at 300 mM NaCl RZS. The reduced RGR with increasing RZS was largely due to the reduced specific leaf area, which was caused by increased leaf succulence as well as by increased leaf dry matter content. No changes in unit leaf rate were observed but increased RZS resulted in increased Na(+) and proline concentrations, reduced K(+), Ca(2+) and Mg(2+) concentrations, lower osmotic potential and increased antioxidant capacity. Proline concentrations of the leaves correlated strongly (r = 0.95) with RZS concentrations and not with plant growth. CONCLUSIONS: Based on its growth response, Crambe maritima can be classified as a salt spray tolerant plant that is sensitive to root zone salinities exceeding 100 mM NaCl.

The immunogenicity and safety of a nicotine vaccine in smokers and nonsmokers: results of a randomized, placebo-controlled phase 1/2 trial.

This randomized, placebo-controlled phase 1/2 trial evaluated the safety and immunogenicity of four doses of a nicotine vaccine in smokers and nonsmokers. Subjects were 21 smokers and 9 nonsmokers in good physical and mental health. They were aged 24-60 years, were recruited from the general public using newspaper advertisements, and were evaluated at University Hospital Maastricht. Each volunteer received four spaced intramuscular injections of 100 microg of purified 3'-aminomethylnicotine conjugated to detoxified Pseudomonas aeruginosa r-exoprotein A or placebo both adsorbed to 800 microg aluminum into the deltoid muscle of alternating arms. Clinical safety was determined by vital signs, reactogenicity, and adverse events, and immunogenicity was measured by enzyme-linked immunosorbent assay. Intensive follow-up for 266 days revealed the vaccine to be well tolerated. We found no significant differences in adverse events between the vaccine and placebo groups. Significant increases in the geometric mean titer (GMT) levels of nicotine-specific antibodies were observed from 7 days after the second vaccination (day 21), reaching nicotine-specific antibody levels of at least 8 microg/ml in half of the subjects (50%) at day 49. A fourth dose administered at day 182 significantly boosted waning antibody levels to a GMT of 10.8 microg/ml at day 217 (95% CI 6.0-19.3). Results showed that the immunogenicity of the vaccine was not impeded by the presence of nicotine. These observations provide evidence in humans that the vaccine we used may represent a feasible strategy for evoking type-specific antibodies against nicotine.

Safety and immunogenicity of a nicotine conjugate vaccine in current smokers.

Immunotherapy is a novel potential treatment for nicotine addiction. The aim of this study was to assess the safety and immunogenicity of a nicotine conjugate vaccine, NicVAX, and its effects on smoking behavior. Smokers (N = 68) were recruited for a noncessation treatment study and assigned to 1 of 3 doses of the nicotine vaccine (50, 100, or 200 microg) or placebo. They were injected on days 0, 28, 56, and 182 and monitored for a period of 38 weeks. Results showed that the nicotine vaccine was safe and well tolerated. Vaccine immunogenicity was dose-related (P < .001), with the highest dose eliciting antibody concentrations within the anticipated range of efficacy. There was no evidence of compensatory smoking or precipitation of nicotine withdrawal with the nicotine vaccine. The 30-day abstinence rate was significantly different across the 4 doses (P = .02), with the highest rate of abstinence occurring with 200 microg. The nicotine vaccine appears to be a promising medication for tobacco dependence.