Calcium cyanamide reduces methane and other trace gases during long-term storage of dairy cattle and fattening pig slurry.

Calcium cyanamide (CaCN2) has been used in agriculture for more than a century as a nitrogen fertilizer with nitrification inhibiting and pest-controlling characteristics. However, in this study, a completely new application area was investigated, as CaCN2 was used as a slurry additive to evaluate its effect on the emission of ammonia and greenhouse gases (GHG) consisting of methane, carbon dioxide, and nitrous oxide. Efficiently reducing these emissions is a key challenge facing the agriculture sector, as stored slurry is a major contributor to global GHG and ammonia emissions. Therefore, dairy cattle and fattening pig slurry was treated with either 300 mg kg-1 or 500 mg kg-1 cyanamide formulated in a low-nitrate CaCN2 product (Eminex®). The slurry was stripped with nitrogen gas to remove dissolved gases and then stored for 26 weeks, during which gas volume and concentration were measured. Suppression of methane production by CaCN2 began within 45 min after application and persisted until the storage end in all variants, except in the fattening pig slurry treated with 300 mg kg-1, in which the effect faded after 12 weeks, indicating that the effect is reversible. Furthermore, total GHG emissions decreased by 99% for dairy cattle treated with 300 and 500 mg kg-1 and by 81% and 99% for fattening pig, respectively. The underlying mechanism is related to CaCN2-induced inhibition of microbial degradation of volatile fatty acids (VFA) and its conversion to methane during methanogenesis. This increases the VFA concentration in the slurry, lowering its pH and thereby reducing ammonia emissions.

Dynamics of Different Buffer Systems in Slurries Based on Time and Temperature of Storage and Their Visualization by a New Mathematical Tool.

Slurry treatments such as acidification and alkalization have proven to be promising solutions to reduce gaseous emission produced by farm animals. The optimization of these technologies requires detailed knowledge of how and to what extent the buffer capacities in slurries will change during storage under the influence of different temperatures, as this may save resources needed to adjust a targeted pH value. Fresh slurries from dairy cows, fattening pigs and sows were collected and stored for 12 weeks under either cold (4.7 ± 1.1 °C) or warm (23.6 ± 2.1 °C) conditions to perform titrations in acidic and alkaline milieu at regular intervals. Based on these results, we successfully verified a new mathematical tool that we have developed to be able to calculate and visualize the most important buffer systems found in the analyzed slurries. Our experimental results showed a strong correlation between the degradation of the volatile fatty acid (VFA) buffer and the emergence of the carbonate buffers, i.e., the HCO3- and the CO32- buffer. Furthermore, a drop in the pH value caused by enhanced microbial production of VFAs can be mitigated by the presence of the NH3 buffer. In conclusion, we demonstrated that the buffers cannot be considered individually but must be interpreted as a complex and interacting system.

Potassium Ion Channel Gene OsAKT1 Affects Iron Translocation in Rice Plants Exposed to Iron Toxicity.

Iron toxicity is one of the most widely spread mineral disorders in anaerobic soils, but the tolerance mechanisms in plants are poorly understood. Here we characterize the involvement of a rice potassium ion channel gene, OsAKT1, in Fe toxic conditions. Two knock-down lines of OsAKT1 together with azygos lines were investigated. Mutant lines did not differ from azygos lines regarding plant growth, gas exchange rate or chlorophyll fluorescence in control conditions. However, loss-of-function of OsAKT1 increased the sensitivity to excess Fe regarding leaf bronzing symptoms, reactive oxygen species generation, leaf spectral reflectance indices, and chlorophyll fluorescence. Fe toxicity leads to largely reduced uptake of other nutrients into shoots, which illustrates the complexity of Fe stress related to multiple mineral disorders. Less potassium uptake in the mutants compared to azygos lines co-occurred with higher amounts of Fe accumulated in the shoot tissues but not in the roots. These results were consistent with a higher level of Fe loaded into the xylem sap of mutants compared to azygos lines in the early phase of Fe toxicity. In conclusion, OsAKT1 is crucial for the tolerance of rice against Fe toxicity as K homeostasis affects Fe translocation from root to shoot.

Diagnosing ozone stress and differential tolerance in rice (Oryza sativa L.) with ethylenediurea (EDU).

Rising tropospheric ozone concentrations in Asia necessitate the breeding of adapted rice varieties to ensure food security. However, breeding requires field-based evaluation of ample plant material, which can be technically challenging or very costly when using ozone fumigation facilities. The chemical ethylenediurea (EDU) has been proposed for estimating the effects of ozone in large-scale field applications, but controlled experiments investigating constitutive effects on rice or its suitability to detect genotypic differences in ozone tolerance are missing. This study comprised a controlled open top chamber experiment with four treatments (i) control (average ozone concentration 16 ppb), (ii) control with EDU application, (iii) ozone stress (average 77 ppb for 7 h daily throughout the season), and (iv) ozone stress with EDU application. Three contrasting rice genotypes were tested, i.e. the tolerant line L81 and the sensitive Nipponbare and BR28. The ozone treatment had significant negative effects on plant growth (height and tillering), stomatal conductance, SPAD value, spectral reflectance indices such as the normalized difference vegetation index (NDVI), lipid peroxidation, as well as biomass and grain yields. These negative effects were more pronounced in the a priori sensitive varieties, especially the widely grown Bangladeshi variety BR28, which showed grain yield reductions by 37 percent. EDU application had almost no effects on plants in the absence of ozone, but partly mitigated ozone effects on foliar symptoms, lipid peroxidation, SPAD value, stomatal conductance, several spectral reflectance parameters, panicle number, grain yield, and spikelet sterility. EDU responses were more pronounced in sensitive genotypes than in the tolerant L81. In conclusion, EDU had no constitutive effects on rice and partly offset negative ozone effects, especially in sensitive varieties. It can thus be used to diagnose ozone damage in field grown rice and for distinguishing tolerant (less EDU-responsive) and sensitive (more EDU-responsive) genotypes.

Inhibition of hypoxia-inducible factor activity in endothelial cells disrupts embryonic cardiovascular development.

Hypoxia-inducible factors (HIFs) are transcriptional regulators that mediate the cellular response to low oxygen levels. By stimulating the expression of angiogenic growth factors such as vascular endothelial growth factor (VEGF), they trigger the neovascularization of tissues under physiologic and pathologic conditions. Here, we have investigated the endothelial cell-autonomous HIF function in blood vessel growth and development by expressing a dominant-negative HIF mutant (HIFdn) that inhibits the transcriptional responses mediated by both HIF-1 and HIF-2, specifically in endothelial cells of transgenic mice. HIFdn transgenic embryos were growth retarded and died around E11.5. Primitive vascular networks were established, but vascular remodeling in the yolk sac and in the embryo proper was defective, and vascular sprouts failed to invade the neuroepithelium. In addition, heart looping was incomplete, and the ventricles of the heart were thin-walled and lacked trabeculation. Similar cardiovascular defects have been observed in Tie2-deficient mouse embryos. Consistently, HIFdn transgenic embryos expressed reduced levels of the endothelial angiopoietin receptor, Tie-2, whereas other endothelial markers, such as PECAM-1, Tie-1, and VE-cadherin were not affected. These results show that HIFs in endothelial cells are essential for embryonic heart and blood vessel development and control angiogenesis and vascular remodeling.

Injection of wild-type cytoplasm and poly(A)+ RNA provokes phenotype rescue in spätzle mutant Drosophila embryos.

spätzle (spz), a maternal effect gene of Drosophila, is involved in the establishment of the dorso-ventral axis during embryogenesis. Eggs from females lacking the spz gene product develop into completely dorsalized embryos, i.e. the ventral and lateral pattern elements fail to develop. Upon injection of either cytoplasm or poly(A)+ RNA from early wild-type embryos, spz embryos develop lateral pattern elements represented by Filzkörper and in the case of injected cytoplasm additional ventral pattern elements represented by ventral setae. Wild-type cytoplasm retains the rescuing activity longer than the poly(A)+ RNA fraction does, and cytoplasm is always more effective in provoking the rescue than poly(A)+ RNA. Mosaic females containing spz germ cells surrounded by spz + tissues were generated by pole cell transplantations; a mutant genotype in the germ cells is sufficient to produce all aspects of the spz mutant phenotype, suggesting that the maternal source of spz gene product is the germ line.