Organic and Mineral Source of Nitrogen Associated With Azospirillum brasilense in Culture of Wheat

Nitrogen fertilization in wheat is the item that most impacts production costs when it comes to fertilization, due to its importance and demand for this crop. Thus, organic fertilization and nitrogen fixing bacteria can be management strategies to supply the nitrogen demand. The objective of this study was to evaluate the impacts of the bacterium A. brasilense associated with organic fertilization and mineral fertilization on some plant parameters and on the final productivity of wheat grains. The experimental design was a randomized block, with 8 treatments and 8 repetitions, with the following treatments: T1: Control; T2: A. brasilense; T3: 100% N-mineral; T4: 100% N-mineral + A brasilense; T5: 50% N-mineral + 50% N-organic; T6: 50% N-mineral + 50% N-organic + A. brasilense; T7: 100% N-organic; T8: 100% N-organic + A. brasilense. The parameters of the plant and the final productivity of wheat grains showed that the use of the bacterium A. brasilense was not an efficient strategy, however, in relation to the fertilization sources in the final grain productivity, the use of urea isolated or associated with organic fertilization did not differ from each other and were superior to the other treatments.

Hanseniaspora vineae and the Concept of Friendly Yeasts to Increase Autochthonous Wine Flavor Diversity

In this perspective, we will explain the concept of “friendly” yeasts for developing wine starters that do not suppress desirable native microbial flora at the initial steps of fermentation, as what usually happens with Saccharomyces strains. Some non-Saccharomyces strains might allow the development of yeast consortia with the native terroir microflora of grapes and its region. The positive contribution of non-Saccharomyces yeasts was underestimated for decades. Avoiding them as spoilage strains and off-flavor producers was the main objective in winemaking. It is understandable, as in our experience after more than 30 years of wine yeast selection, it was shown that no more than 10% of the isolated native strains were positive contributors of superior flavors. Some species that systematically gave desirable flavors during these screening processes were Hanseniaspora vineae and Metschnikowia fructicola. In contrast to the latter, H. vineae is an active fermentative species, and this fact helped to build an improved juice ecosystem, avoiding contaminations of aerobic bacteria and yeasts. Furthermore, this species has a complementary secondary metabolism with S. cerevisiae, increasing flavor complexity with benzenoid and phenylpropanoid synthetic pathways practically inexistent in conventional yeast starters. How does H. vineae share the fermentation niche with other yeast strains? It might be due to the friendly conditions it creates, such as ideal low temperatures and low nitrogen demand during fermentation, reduced synthesis of medium-chain fatty acids, and a rich acetylation capacity of aromatic higher alcohols, well-known inhibitors of many yeasts. We will discuss here how inoculation of H. vineae strains can give the winemaker an opportunity to develop ideal conditions for flavor expression of the microbial terroir without the risk of undesirable strains that can result from spontaneous yeast fermentations.

Nitrogen Fixation in Subtropical Seagrass Sediments: Seasonal Patterns in Activity in Santa Rosa Sound, Florida, USA

Seagrass beds are important coastal habitats that are diminishing globally. Nitrogen, a key nutrient, often limits seagrass growth. Nitrogen fixation provides new, bioavailable nitrogen to the plants. This study explores its importance and factors controlling rates in sediments colonized by two dominant taxa in Northwest Florida, Thalassia testudinum and Halodule wrightii, compared to unvegetated sediments. We hypothesized that nitrogen fixation rates would be greater in seagrass colonized sediments, particularly during high growth periods. We expected to observe a positive relationship between rates and porewater sulfide concentrations because sulfate reducers were the dominant diazotrophs in similar studies. Rates were higher in vegetated areas. In H. wrightii beds, nitrogen fixation was driven by the decreased availability of porewater ammonium relative to phosphorus. In T. testudinum beds, rates were highest during winter. Organic matter may be a controlling factor in all substrate types albeit the exact mechanism driving nitrogen fixation differs slightly. During the summer and fall, nitrogen fixation provided between 1–15% of T. testudinum nitrogen demand. Annually, nitrogen fixation provided 4% and 1% of T. testudinum and H. wrightii nitrogen demand, respectively. Nitrogen fixation was an important source of nitrogen during periods of senescence and dormancy when organic matter content was high.

Internal ammonium excess induces ROS-mediated reactions and causes carbon scarcity in rice

Background: Overuse of nitrogen fertilizers is often a major practice to ensure sufficient nitrogen demand of high–yielding rice, leading to persistent NH4+ excess in the plant. However, this excessive portion of nitrogen nutrient does not correspond to further increase in grain yields. For finding out the main constraints related to this phenomenon, the performance of NH4+ excess in rice plant needs to be clearly addressed beyond the well-defined root growth adjustment. The present work isolates an acute NH4+ excess condition in rice plant from causing any measurable growth change and analyses the initial performance of such internal NH4+ excess. Results: We demonstrate that the acute internal NH4+ excess in rice plant accompanies readily with a burst of reactive oxygen species (ROS) and initiates the downstream reactions. At the headstream of carbon production, photon caption genes and the activity of primary CO2 fixation enzymes (Rubisco) are evidently suppressed, indicating a reduction in photosynthetic carbon income. Next, the vigorous induction of glutathione transferase (GST) genes and enzyme activities along with the rise of glutathione (GSH) production suggest the activation of GSH cycling for ROS cleavage. Third, as indicated by strong induction of glycolysis / glycogen breakdown related genes in shoots, carbohydrate metabolisms are redirected to enhance the production of energy and carbon skeletons for the cost of ROS scavenging. As the result of the development of these defensive reactions, a carbon scarcity would accumulatively occur and lead to a growth inhibition. Finally, a sucrose feeding cancels the ROS burst, restores the activity of Rubisco and alleviates the demand for the activation of GSH cycling. Conclusion: Our results demonstrate that acute NH4+ excess accompanies with a spontaneous ROS burst and causes carbon scarcity in rice plant. Therefore, under overuse of N fertilizers carbon scarcity is probably a major constraint in rice plant that limits the performance of nitrogen.

Internal ammonium excess induces ROS-mediated reaction and causes carbon scarcity in rice

Background: Overuse of nitrogen fertilizers is often applied to satisfy strong nitrogen demand of high-yielding rice, leading to persistent NH 4 + excess in the plant. However, the mechanisms constraining the effectiveness of elevated plant NH 4 + in plant growth and grain yield of rice are not sufficiently addressed. In the current study, we attempt to real the nature or mode-of-action of such internal NH 4 + excess in rice, and the efficient coordination measure with current high N fertilizer cropping systems is investigated. Results: By mimicking a rapid accumulation of plant NH 4 + and an RNA-Seq analysis, the present work reveals that internal NH 4 + excess in rice plant initiates a burst of reactive oxygen species (ROS) and triggers probably specifically the activation of glutathione transferase (GST)-mediated glutathione cycling for ROS cleavage. Meanwhile, the suppression of the expression of genes involved in photon caption and the activity of primary CO 2 fixation enzymes (Rubisco), provides implications of a reduction in photosynthetic carbon income. Along the progress of NH 4 + / ROS stresses, enhanced energy-producing processes (carbon breakdown) take place as indicated by strong induction of glycolysis related genes to meet the demand of energy consuming activation of ROS-cleavaging systems. The development of these defensive reactions causes a sugar scarcity in the plant that accumulatively leads to growth inhibition. To the opposite direction, a sucrose feeding treatment to the roots renders the accumulation of free NH 4 + and ROS, partly restores the activities of photosynthetic CO 2 fixation and thus alleviates the scarcity in active carbon source. Conclusion: Our results demonstrate the necessity of efficient carbon coordination, aiming at improving the nitrogen performances under current N fertilizer overuse circumstances.