Community profiling and gene expression of fungal assimilatory nitrate reductases in agricultural soil

Although fungi contribute significantly to the microbial biomass in terrestrial ecosystems, little is known about their contribution to biogeochemical nitrogen cycles. Agricultural soils usually contain comparably high amounts of inorganic nitrogen, mainly in the form of nitrate. Many studies focused on bacterial and archaeal turnover of nitrate by nitrification, denitrification and assimilation, whereas the fungal role remained largely neglected. To enable research on the fungal contribution to the biogeochemical nitrogen cycle tools for monitoring the presence and expression of fungal assimilatory nitrate reductase genes were developed. To the ∼100 currently available fungal full-length gene sequences, another 109 partial sequences were added by amplification from individual culture isolates, representing all major orders occurring in agricultural soils. The extended database led to the discovery of new horizontal gene transfer events within the fungal kingdom. The newly developed PCR primers were used to study gene pools and gene expression of fungal nitrate reductases in agricultural soils. The availability of the extended database allowed affiliation of many sequences to known species, genera or families. Energy supply by a carbon source seems to be the major regulator of nitrate reductase gene expression for fungi in agricultural soils, which is in good agreement with the high energy demand of complete reduction of nitrate to ammonium

Germinação de sementes de cenoura osmoticamente condicionadas e peletizadas com diversos ingredientes Germination of carrot seed primed and pelleted with several ingredients

A semente de cenoura caracteriza-se por ser relativamente pequena, o que dificulta o processo de distribuição, tornando a mecanização por semeadeiras convencionais uma prática difícil. A técnica da peletização tem sido utilizada visando a melhoria da distribuição de sementes e o estabelecimento de plântulas no campo. As sementes peletizadas geralmente apresentam menor velocidade de germinação quando comparadas com as sementes nuas do mesmo lote. O condicionamento osmótico tem sido utilizado para aumentar a velocidade de germinação de sementes. Neste estudo foram avaliados materiais cimentantes para a peletização de sementes e verificadas as relações existentes entre o condicionamento osmótico e a germinação das sementes peletizadas de cenoura cv. Alvorada. A peletização foi feita utilizando-se, como material de enchimento, a mistura de microcelulose e areia fina em volumes iguais e, para enchimento foram avaliados cinco materiais cimentantes: bentonita, methocel, opadry, rhoximat e goma arábica. Sementes peletizadas receberam ou não o acabamento com iriodin. Uma testemunha (sementes nuas) foi incluída no ensaio. Em outro estudo, sementes foram osmoticamente condicionadas em solução aerada de polietileno glicol e peletizadas imediatamente após o condicionamento osmótico ou após a secagem. Os produtos rhoximat e opadry apresentaram as melhores características como material cimentante, formando uma fina camada de revestimento, que resultou na formação de péletes com superfície lisa, uniforme e ótima aparência externa. Em geral, péletes apresentaram uma ligeira redução na porcentagem e na velocidade de germinação, em comparação às sementes não peletizadas, com diferenças maiores para os péletes que receberam o acabamento com iriodin. O condicionamento osmótico aumentou a velocidade de germinação das sementes peletizadas de cenoura.<br>Carrot seeds are small and the distribution in the field by seeders is generally very difficult. Seed pelleting has been used to improve sowing and consequently the stand establishment. Pelleted seeds generally present lower germination rate than raw seeds from the same seed lot. Seed priming has been used to increase germination rate of several species. Various binder materials for seed pelleting were evaluated and the relation between the osmoconditioning and germination of pellet seeds verified, using 'Alvorada' carrot cultivar. The pellet was obtained through a mixture of equal parts of microcelulose and sand as filling materials; five binder materials were also evaluated: bentonite, methocel, opadry, rhoximat and arabic gum. Part of the pelleted seeds received an external coat treatment (iriodin). Raw seeds were included as control. In another study, seeds were primed in an aerated solution of polyethylene glycol, dried and then pelleted. Rhoximat and opadry showed better characteristics as binder materials presenting pellets with smooth surface, uniform and excellent external appearance. In general, seed pellets showed a slight decrease of the germination rate and total germination compared to raw seeds, with greather differences for pellets finished with iriodin. Priming enhanced the germination rate of pelleted carrot seeds