Humic Acid Alleviates Fe Chlorosis in Graminaceous Plants Through Coordinated Fe-Dependent and Fe-Independent Mechanisms.

Many studies have shown the close relationship between the beneficial action of soil and sedimentary humic acids on the growth of plants cultivated in calcareous soils and their ability to improve Fe plant nutrition. These results have been ascribed to the humic acid (HA) capability to improve Fe solubility and bioavailability. However, other effects more related to a humic acid action on the specific mechanisms activated in roots of plants under Fe deficiency cannot be ruled out.

Shoot iron status and auxin are involved in iron deficiency-induced phytosiderophores release in wheat.

Background: The release of phytosiderephores (PS) to the rhizosphere is the main root response to iron (Fe) deficiency in graminaceous plants. We have investigated the role of the Fe status in the shoot as well as of the signaling pathways controlled by three relevant phytoregulators - indolacetic acid (IAA), ethylene and nitric oxide (NO) - in the regulation of this root response in Fe-starved wheat plants. To this end, the PS accumulation in the nutrient solution and the root expression of the genes encoding the nicotianamine aminotransferase (TaNAAT) and ferritin (TaFER) have been evaluated in plants subjected to different treatments.

Efficiency of urease and nitrification inhibitors in reducing ammonia volatilization from diverse nitrogen fertilizers applied to different soil types and wheat straw mulching.

Background: Some authors suggest that the absence of tillage in agricultural soils might have an influence on the efficiency of nitrogen applied in the soil surface. In this study we investigate the influence of no-tillage and soil characteristics on the efficiency of a urease inhibitor (N-(n-butyl)thiophosphoric triamide, NBPT) and a nitrification inhibitor (diciandiamide, DCD) in decreasing ammonia volatilization from urea and ammonium nitrate (AN), respectively.

Results: The results indicate that ammonia volatilization in soils amended with urea was significantly higher than in those fertilized with AN.

Structural characteristics of phosphoramide derivatives as urease inhibitors. Requirements for activity.

Taking as a reference the structural characteristics of a set of compounds that act as jack bean ( Canavalia ensiformis) urease inhibitors, namely, phenylphosphorodiamidate (PPD), N- n-butylthiophosphorictriamide (NBPT), and N- n-butylphosphorictriamide (NBPTO), we have studied the structure-activity relationships of a series of phosphoramide derivatives for which the activity as urease inhibitors in both in vitro and in vivo assays is known. Molecular modeling studies were carried out, and the results highlighted the relevance of characteristics such as the presence of intramolecular hydrogen bonds, the volume of the fragment involved in the enzyme interaction, and the degree of conformational freedom as well as the HOMO orbital and atomic orbital contributions to the HOMO orbital, electron density, and PEM distributions on the activity of these compounds as urease inhibitors. These data, along with the preliminary docking study carried out, allow us to propose a union mode to the active site of the enzyme for these compounds.

Design, synthesis, and biological evaluation of phosphoramide derivatives as urease inhibitors.

The design, synthesis, and biological evaluation of phosphoramide derivatives as urease inhibitors to reduce the loss of ammonia has been carried out. Forty phosphorus derivatives were synthesized and their inhibitory activities evaluated against that of jack bean urease. In addition, in vivo assays have been carried out.

Development and agronomical validation of new fertilizer compositions of high bioavailability and reduced potential nutrient losses.

To optimize the economical cost of each unit of fertilizer applied and to reduce the environmental contamination caused by nutrient losses, the development of highly efficient granulated fertilizers is of great importance. This study proposes a strategy that consists of developing specific fertilizers having nutrient release patterns that are dependent on plant activity in the rhizosphere. This type of fertilizer is named "rhizosphere-controlled fertilizer" (RCF fertilizer).