The effect of sulfur on the response of cotton to urea under alkali soil conditions in pot experiments

Summary The effect of sulfur (S) placement and S rate on the efficiency of urea (U) relative to ammonium sulfate (AS) and ammonium nitrate (AN) for cotton were examined in a pot experiment using sandy clay loam soil (pH 7.9). The results showed that AS and AN application in the absence of S increased the yield than U partly because U-induced damage to plants. The combined application of the N sources with S increased the yields and that, the placement of S in the seed horizon in contact with N was more effective than mixing throughout the soil especially with U. These effects were observed with three cotton cultivars. The addition of S to a maximum of 1.5 g/pot gave further increases in yields or the N content of leaves for U, AS or AN. Using the least squares method, it was found that the presence of S significantly increased the efficiency of U than AS or AN. Incubation of S and the N sources with S in the soil was carried out to understand the growth conditions of cotton fertilized by U in alkalin soil. In the case of U-soil system, the pH increased. NO₂−N accumulated and considerable loss of N took place. The pH, NO₂−N accumulation and the loss of N decreased with S increments.     

Comparison of the efficiency of urea,aqueous ammonia and ammonium sulphate as nitrogen fertilizers

Summary Nitrogen-15 labelled urea, aqueous NH₃ and (NH₄)₂SO₄ were applied to soils contained in pots. The fertilizers were injected in 5 cm³ of solution, 3.5 cm below the soil surface, to simulate a fertilizer band in the field. Ryegrass (Lolium perenne) was planted, and several cuttings and roots were harvested. Efficiency was determined as the recovery of fertilizer-N in the plant tissues and soil.Total recovery varied from 94 to 100%. There was no significant difference between the total recovery of the 3 fertilizer forms, although recovery in the soil component was lower for (NH₄)₂SO₄ than for urea or NH₃. There was a significant difference in total recovery between soils due to the soil component. Only small amounts of¹⁵N were not recovered, whereas laboratory experiments reported elsewhere had demonstrated that substantial gaseous losses of N as N₂, N₂O and NO +NO₂ occurred in these soils during nitrification of added NH₃ fertilizer.     

The function of the pentose phosphate pathway in Phaseolus mungo hypocotyls

The metabolism of d-gluconate-[1-¹⁴C] and -[6-¹⁴C] by segments from etiolated hypocotyls of Phaseolus mungo has been studied. The release of ¹⁴CO₂ from gluconate-[1-¹⁴C] was greater than that from gluconate-[6-¹⁴C] in all parts of hypocotyls examined. Incorporation of the radioactivity from gluconate-[6-¹⁴C] into RNA, lignin and aromatic amino acid fractions was greater in the upper (younger) part of the hypocotyls. Incorporation into sugars was greater in the lower (more mature) parts.     

Aluminium Stress Affects Nitrogen Fixation and Assimilation in Soybean (Glycine max L.)

Nitrogen fixation and assimilation in nodules and roots were studied in soybean (Glycine max L.) exposed to different levels of aluminium (Al) stress (0, 50, 200 and 500 μM). Al at 500 μM induced oxidative stress, which became evident from an increase in lipid peroxidation accompanied by a concomitant decline in antioxidant enzyme activities and leghaemoglobin breakdown. Consequently, there was also a reduction in nitrogenase activity. However, the leghaemoglobin levels and nitrogenase activity were unexpectedly found to be higher in nodules when the plants were treated with 200 μM Al. Of the enzymes involved in nitrogen assimilation, the activity of glutamate dehydrogenase-NADH was reduced in nodules under Al stress, but it was significantly higher in roots at 500 μM Al as compared to that in the control. In nodules, the glutamine synthetase/glutamate synthase-NADH pathway, assayed in terms of activity and expression of both the enzymes, was inhibited at >50 μM Al; but in roots this inhibitory effect was apparent only at 500 μM Al. No significant changes in ammonium and protein contents were recorded in the nodules or roots when the plants were treated with 50 μM Al. However, Al at ≥200 μM significantly increased the ammonium levels and decreased the protein content in the nodules. But these contrasting effects on ammonium and protein contents due to Al stress were observed in the roots only at 500 μM Al. The results suggest that the effect of Al stress on nitrogen assimilation is more conspicuous in nodules than that in the roots of soybean plants.     

Transferrin Modifications and Lipid Peroxidation: Implications in Diabetes Mellitus

Free iron is capable of stimulating the production of free radicals which cause oxidative damage such as lipid peroxidation. One of the most important mechanisms of antioxidant defense is thus the sequestration of iron in a redox-inactive form by transferrin. In diabetes mellitus, increased oxidative stress and lipid peroxidation contribute to chronic complications but it is not known if this is related to abnormalities in transferrin function. In this study we investigated the role of transferrin concentration and glycation. The antioxidant capacity of apotransferrin to inhibit lipid peroxidation by iron-binding decreased in a concentration-dependent manner from 89% at <formula>≥2 mg/ml</formula> to 42% at 0.5 mg/ml. Pre-incubation of apotransferrin with glucose for 14 days resulted in a concentration-dependent increase of glycation: 1, 5 and 13 μmol fructosamine/g transferrin at 0, 5.6 and 33.3 mmol/l glucose respectively, p<0.001. This was accompanied by a decrease in the iron-binding antioxidant capacity of apotransferrin. In contrast, transferrin glycation by up to 33.3 mmol/l glucose did not affect chemiluminescence-quenching antioxidant capacity, which is iron-independent. Colorimetric evaluation of total iron binding capacity in the presence of an excess of iron (iron/transferrin molar ratio=2.4) also decreased from 0.726 to 0.696 and 0.585 mg/g transferrin after 0, 5.6 and 33.3 mmol/l glucose, respectively, p<0.01. In conclusion, these results suggest that lower transferrin concentration and its glycation can, by enhancing the pro-oxidant effects of iron, contribute to the increased lipid peroxidation observed in diabetes.     

Cloning of the Lentinula edodes B mating-type locus and identification of the genetic structure controlling B mating

During the life cycle of heterothallic tetrapolar Agaricomycetes such as Lentinula edodes (Berk.) Pegler, the mating type system, composed of unlinked A and B loci, plays a vital role in controlling sexual development and resulting formation of the fruit body. L. edodes is produced worldwide for consumption and medicinal purposes, and understanding its sexual development is therefore of great importance. A considerable amount of mating type factors has been indicated over the past decades but few genes have actually been identified, and no complete genetic structures of L. edodes B mating-type loci are available. In this study, we cloned the matB regions from two mating compatible L. edodes strains, 939P26 and 939P42. Four pheromone receptors were identified on each new matB region, together with three and four pheromone precursor genes in the respective strains. Gene polymorphism, phylogenetic analysis and distribution of pheromone receptors and pheromone precursors clearly indicate a bipartite matB locus, each sublocus containing a pheromone receptor and one or two pheromone precursors. Detailed sequence comparisons of genetic structures between the matB regions of strains 939P42, 939P26 and a previously reported strain SUP2 further supported this model and allowed identification of the B mating type subloci borders. Mating studies confirmed the control of B mating by the identified pheromone receptors and pheromones in L. edodes.     

Characterization of reduced susceptibility to chlorhexidine among Gram-negative bacteria

Chlorhexidine gluconate (CHG) is one of the most commonly used antiseptic, acting against Gram-negative, Gram-positive bacteria, yeast and fungi. However, over use may lead to reduced susceptibility of different bacteria to CHG. This study aimed to characterize the CHG susceptibility among Gram-negative strains in Israel, to evaluate factors that may affect this susceptibility, and to compare CHG susceptibility between ESBLs bacteria to strains without these enzymes. Pseudomonas aeruginosa, Proteus mirabilis, Klebsiella spp, Escherichia coli, and Acinetobacter baumannii were isolated from clinical samples of 193 patients hospitalized at Padeh–Poriya Medical Center. Phenotypic CHG susceptibility was assessed by determining minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The highest CHG MIC was found among P. mirabilis. The differences between the CHG MIC values among the different strains were statistically significant (p < 0.001). ESBL-positive strains had higher MIC values as compared to ESBL-negative strains (p = 0.030). A significant association was found between CHG susceptibility and sample source (p = 0.015). In conclusion, the information gathered here significantly improves our knowledge on the reduced susceptibility to CHG among Gram-negative bacteria in Israel. Moreover, ESBL-positive bacteria are less susceptible to CHG and finally, bacteria in sputum, wounds, and body fluids are less CHG-susceptible.     

Effects of 2,6-dichlorobenzonitrile on differentiation to tracheary elements of isolated mesophyll cells of Zinnia elegans and formation of secondary cell walls

Seeds of Caesulia axillaris Roxb. displayed an absolute light requirement for germination throughout the period of dry storage at 28°C. The seeds were found to show a gradual increase in percent germination with storage time - reaching a maximum value between 8-14 months and then a sharp decline. Percent water uptake and photosensitivity were at maximum after a 5-day imbibition period in the dark in both seedlots studied. Seedlot I, which was only marginally responsive to far-red light, showed a nearly complete red-far-red reversal effect in contrast to seedlot II. The latter also displayed a considerable promotion of germination in far-red light. Interestingly, a noticeable degree of heterogeneity, besides the one observed in both seedlots with reference to red light, was found to exist in seedlot II for far-red light. Exogenous application of nitrate and ammonium, at the levels occurring in soil during seed germination/seedling emergence phase of the plant in nature, promoted a considerable proportion of high Ø-requiring seeds to germinate under irradiation conditions establishing low Ø-value. The probable ecological implication of this reponse has been discussed. Little correlation was found between the requirement for an exogenous supply of nitrate and the endogenous nitrate level in the seeds in their response to far-red light.     

Response of coastal phytoplankton to ammonium and nitrate pulses: seasonal variations of nitrogen uptake and regeneration

Seasonal variation in uptake and regeneration of ammonium and nitrate in a coastal lagoon was studied using ¹⁵N incorporation in particulate matter and by measuring changes in particulate nitrogen. Uptake and regeneration rates were two orders of magnitude lower in winter than in summer. Summer uptake values were 2.8 and 2.2 mol N.l^–1.d^–1 for ammonium and nitrate, respectively. Regeneration rates were 2.9 and 2.1 mol N.l^–1.d^–1 for ammonium and nitrate respectively. Regeneration/uptake ratios were often below one, indicating that water column processes were not sufficient to satisfy the phytoplankton nitrogen demand. This implies a role of other sources of nitrogen, such as macrofauna (oysters and epibionts) and sediment. Phytoplankton was well adapted to the seasonal variations in resources, with mixotrophic dinoflagellates dominant in winter, and fast growing diatoms in summer. In winter and spring, ammonium was clearly preferred to nitrate as a nitrogen source, but nitrate was an important nitrogen source in summer because of high nitrification rates. Despite low nutrient levels, the high rates of nitrogen regeneration in summer as well as the simultaneous uptake of nitrate and ammonium allow high phytoplankton growth rates which in turn enable high oyster production.     

Is xanthine dehydrogenase involved in response of pea plants (<Emphasis Type="Italic">Pisum sativum</Emphasis> L.) to salinity or ammonium treatment?

The effect of salinity and different nitrogen sources on the level of xanthine dehydrogenase (XDH) activity in roots and leaves of pea plants was investigated. Two bands of xanthine dehydrogenase activity (XDH-R2, XDH-R3) were detected in roots after native PAGE and staining with hypoxanthine as substrate. Only one band of XDH activity (XDH-L1) was detected in leaf extracts. Within leaves of three different ages the highest XDH activity was detected in young leaves both under control as well as stress conditions. Salinity did not affect significantly the activity of XDH in pea roots, however, depressed XDH activity in leaves. A significant increase of XDH activity both in roots and leaves was observed only when ammonium was applied as the sole N source. Increased concentration of ureides in the xylem sap of pea plants was observed for both ammonium and high salt treatments, although the higher content of ureides in the xylem sap of 100 mM NaCl treated plants may be rather a result of lower rate of exudation from roots than of increased root ureide biosynthesis. Thus, the changes of root and leaf XDH activity in pea plants seem to be tightly correlated with ureide synthesis that is induced by NH ₄ ⁺ , the product of N fixation, and rather than by salinity. A contribution of pea XDH in increased oxygen species or uric acid production under saline conditions seems to be less than likely.