Sufficient Nitrogen Supply Research Articles

Nutrient enrichment and selective predation by zooplankton promote Microcystis (Cyanobacteria) bloom formation

An experiment was conducted with a natural freshwater phytoplankton community from a eutrophic pond to investigate the combined effects of phytoplankton community competitive interactions, nutrient enrichment and zooplankton on Microcystis bloom formation. The pond water initially had a very low concentration of Microcystis, but the total phytoplankton biomass as chlorophyll a reached ∼10 μg L -1 in summer. The pond water was incubated outdoors at natural temperature and light with a 2 x 2 factorial manipulation of nutrient (nutrient additions versus no additions) with and without zooplankton. The interaction of a two-phase nutrient addition (a net increase in concentrations of 250.0 μM N and 16.1 μM P each time) and the presence of zooplankton significantly altered phytoplankton community composition. When the water initially contained zooplankton, nitrogen and phosphorus enrichment promoted a surface Microcystis bloom. However, when the zooplankton was removed from the water at the start of the experiment, no surface Microcystis bloom formed, regardless of nutrient additions. Chlorophyta dominated in the absence of zooplankton, when the same nutrient was provided. Our results demonstrate that Microcystis bloom formation in this eutrophic water body at a mean temperature of about 36°C at 14:00 h was closely related to the initial presence of zooplankton and a sufficient supply of nitrogen and phosphorus. We believe this is one of the first demonstrations of zooplankton controlling Microcystis bloom formation in a water body previously free of surface cyanobacterial blooms.

Biological Nitrogen Fixation on Legume

Nitrogen (N) is one of the major limiting factors for crop growth and is required in adequate amount, due to its function as protein and enzyme components. In general, plants need sufficient nitrogen supply at all levels of growth, especially at the beginning of growth phase. Therefore, the availability of less expensive N resources would reduce the production cost. The increasing use of chemical fertilizer would probably disturb soil microorganisms, reduce the physical and chemical characteristics of soil because not all of N based fertilizer applied can be absorbed by the plants. Approximately only 50% can be used by crops, while the rest will be altered by microorganism into unavailable N for crops or else dissappear in the form of gas. Leguminous crops have the capacity to immobilize N2 and convert into the available N if innoculated with Rhizobium . The amount of N2 fixed varies depending on legume species and their environment. Key words: Nitrogen fixation, legume

Applicability of Different Indices to Evaluate Nutrient Status of Winter Wheat in the Organic System

ABSTRACT Nitrogen (N), phosphorus (P), and potassium (K) nutrient status of two winter wheat cultivars (Kobra and Juma) in the organic crop production system was compared with integrated and conventional systems. This research was conducted between 1998 and 2000 at the Experimental Station in Osiny (Lublin province, Poland) on a grey-brown podzolic soil. To determine N, P, and K contents shoot samples of wheat were taken at the shooting and earing growth stages. Measurements of chlorophyll content were performed with a chlorophyll meter (SPAD) to estimate N nutrient status. Four different methods [Nitrogen Nutrient Index (NNI), Soil Plant Analysis Development (SPAD), Diagnostic Recommendation Integrated System (DRIS), and Sufficiency Range (SR)] of nutrient status evaluation were compared. Nitrogen (N) and potassium (K) nutrient status of wheat cultivated in the organic system was lower compared with the other farming systems. Assuring sufficient supply of nitrogen to cereals under the conditions of organic farming is particularly difficult in early growth stages. In the integrated and conventional systems wheat was sufficiently supplied with NPK. Kobra cv. proved to be more adapted to the organic system. Results indicate that classical nutrient status indices are of lesser use for organic farming.

COVERCROPS IN BLACKCURRANT (RIBES NIGRUM)

With the objective to identify the effect of soil cultivation and nitrogen supply in organic production of blackcurrant a field trial was planted autumn 1996 under unsprayed conditions. The bush rows were cleaned mechanically for weed, and cover crops were established in the alleyways. During establishment all four cover crops gave a sufficient nitrogen supply. The level of nitrogen in soil and the growth were smallest in the annual sown cover crop. Miniritzotrons were used to follow blackcurrant root growth in total mechanical cleaned plots and plots with sown alleyways. The maximum root dept of blackcurrants of 125 cm were obtained direct under the bush in autumn 1998, whereas the roots only were present down to 40 cm 1.5 meters from the centre of the row. The variety ‘Titania’ had a deeper root pattern than ‘Ben Lomond’. There were no significant yield differences among the soil treatments. There was a tendency to a higher yield for ‘Titania’ in 2000 in the annual sown cover crop, probably due to the deeper root pattern of ‘Titania’ and thereby less susceptibility to mechanical root damage. ‘Titania’ had the highest yield in the two cropping years 1999 and 2000; whereas, ‘Ben Lomond’ had a very low yield due to severe infections of American gooseberry mildew (Sphaerotheca mors-uvae); which caused very little shoot growth. ‘Farleigh’ was susceptible to white pine blister rust (Cronartium ribicola) and infections of leaf spot (Gloeosporidiella ribis) occurred every year. ‘Titania’ and ‘Intercontinental’ had the best field resistance to diseases.

Urea uptake and urease activity in Corynebacterium glutamicum.

When Corynebacterium glutamicum is grown with a sufficient nitrogen supply, urea crosses the cytoplasmic membrane by passive diffusion. A permeability coefficient for urea diffusion of 9 x 10(-7) cm s-1 was determined. Under conditions of nitrogen starvation, an energy-dependent urea uptake system was synthesized. Carrier-mediated urea transport was catalyzed by a secondary transport system linked with proton motive force. With a Km for urea of 9 microM, the affinity of this uptake system was much higher than the affinity of urease towards its substrate (Km approximately 55 mM urea). The maximum uptake velocity depended on the expression level and was relatively low [2-3.5 nmol min-1 (mg dry wt.)-1].

Functional and Genetic Characterization of the (Methyl)ammonium Uptake Carrier of Corynebacterium glutamicum

Under nitrogen starvation conditions, Corynebacterium glutamicum was found to take up methylammonium at a rate of 20 +/- 5 nmol.min-1.(mg dry weight)-1. The specific activity of this uptake was 10-fold lower when growing the cells under sufficient nitrogen supply, indicating a tight regulation on the expression level. The methylammonium uptake showed Michaelis-Menten kinetics with an Km of 44 +/- 7 microM and was completely inhibited by the addition of 10 microM ammonium. This finding and the fact that methylammonium was not metabolized by C. glutamicum strongly suggests that the uptake carrier actually represents an ammonium uptake system. Methylammonium uptake was strictly dependent on the membrane potential. From the pH optimum and the accumulation of methylammonium in equilibrium, it could be deduced that only one net charge is transported and, thus, that methylammonium is taken up in its protonated form via an uniport mechanism. The amt gene encoding the (methyl)ammonium uptake system was isolated and characterized. The predicted gene product of amt consists of 452 amino acids (Mr = 47,699) and shows 26-33% identity to ammonium transporter proteins from Saccharomyces cerevisiae and Arabidopsis thaliana. According to the hydrophobicity profile, it is an integral membrane protein containing 10 or 11 membrane-spanning segments.

Influence of nitrogen supply on the response of clones of birch (Betula pendula Roth.) to ozone

summaryClonal birch (Betula pendula Roth.) seedlings were exposed to slightly higher than ambient levels of ozone and different levels of nitrogen supply under open‐field conditions in three experiments: (1) three 2‐year‐old clones exposed to ozone and 74/150 kg N ha−1 y−1 for two growing seasons, (2) three 2‐year‐old clones under a corresponding exposure regime for one growing season and (3) one 2‐year‐old clone exposed to ozone and 37/74/150 kg N ha−1 y−1 for one growing season. The cumulative ozone exposures were 1–5 x (1992) and 1–7 x (1993) higher than ambient levels. In these experiments no significant differences between the clones were found in their response to each treatment. Ozone exposure reduced the mean leaf size and the leaf area, accelerated autumn yellowing and loss of leaves, and increased the palisade layer thickness. High nitrogen availability increased the height growth, the mean leaf size, the leaf area, the shoot/root ratio, the leaf water content and the stem dry weight, but decreased the number of leaves and the leaf dry mass per area, and retarded autumn senescence of leaves. It also reduced the leaf and palisade layer thickness and increased the intercellular space of the palisade layer. Significant interactions between ozone and nitrogen supply were found as an increase in leaf biomass production, root dry weight and spongy intercellular space, and as a decrease in leaf loss, yellowing of leaves and palisade layer thickness. The results suggest that sufficient nitrogen supply can confer the birch with greater resistance to ozone.

Quantification of the Daily Cytokinin Transport from the Root to the Shoot of Urtica dioica L.*

AbstractCytokinins are predominantly root‐born phytohormones which are distributed in the shoot via the xylem stream. In the hormone message concept they are considered as root signals mediating the transport of the photosynthates to the various sinks of a plant. In this paper the cytokinin relations of Urtica dioica L., the stinging nettle, are described, based on the daily flux from the roots to the shoot. Trans‐zeatin‐type cytokinins predominate in the various tissues of Urtica (Wagner and Beck, 1993), and accordingly trans‐zeatin riboside and trans‐zeatin are the forms transported by the xylem sap. The daily time‐course of cytokinin concentration in root pressure exudates and in xylem sap collected from a petiole after pressurizing the root bed showed high concentrations in the morning, followed by a substantial drop to a level of 15–30% of the initial concentration which was then maintained during the afternoon. This time‐course is interpreted as resulting from continuous synthesis and exudation of cytokinins into the xylem fluid of the roots whose cytokinin concentration is then modified by the dynamics of the transpiration stream. Loading of cytokinins into the xylem sap could be enhanced several times by increasing the flux rate of the xylem stream to the maximal transpiration rate when a maximum export rate was reached. The total daily cytokinin gain by the shoot depended on the nitrogen status of the plant. Roots of Urtica plants grown on a sufficient nitrogen supply had a significantly higher cytokinin content and exuded more cytokinins into the shoot than those of plants raised under nitrogen shortage. A positive correlation was found between the steady rates of cytokinin export measured during the afternoon and the shoot to root‐ratios of biomass which, in turn, corresponded to the nitrogen status of the plants.

The photosynthetic machinery in prochlorophytes: Structural properties and ecological significance

Abstract The Prochlorophytes are a diverse group of photosynthetic prokaryotes which falls within the cyanobacterial lineage, yet lack phycobilisomes as light harvesting structures. Instead, the Prochlorophytes have a light-harvesting apparatus composed of the higher plant pigments chlorophylls a and b . This review discusses antenna structures, photosynthetic properties and evolutionary relationships among these bacteria, with focus on the role of photosynthesis in their natural habitat. Most of the available information is obtained from studies on Prochlorothrix , the model organism of this group in laboratory studies. Our analysis yields a consensus from studies on two Prochlorophytes, Prochloron and Prochlorothrix , as to how the thylakoid membrane is organized. Lack of laboratory studies on an abundant third Prochlorophyte, Prochlorococcus , does not (yet) allow to include this species in the consensus. Overall, we propose that the structure of the light-harvesting complexes from Prochlorophytes is very different from those of chloroplast systems, and is evolutionarily very ancient. The light-harvesting apparatus is considered to maintain a strong structural and functional association with Photosystem I in both Prochlorothrix and Prochloron . Photosystem It in Prochlorothrix differs from other photosynthetic systems in structural and functional properties of both donor and acceptor sides of its reaction center. A demonstrated capacity for Photosystem I-dependent anoxygenic photosynthesis in Prochlorothrix may indicate that there is an increased dependence on cyclic photophosphorylation in these organisms. A description of the natural habitats of the Prochlorophytes has been employed as a jumping board for speculation on the role of the photosynthetic apparatus in occupying, proliferating and surviving in their ecological niches. Prochlorophytes seem to thrive in stable environments of low light, sufficient nitrogen supply and possibly the presence of essential organic solutes.

The photosynthetic machinery in prochlorophytes: Structural properties and ecological significance

The Prochlorophytes are a diverse group of photosynthetic prokaryotes which falls within the cyanobacterial lineage, yet lack phycobilisomes as light harvesting structures. Instead, the Prochlorophytes have a light-harvesting apparatus composed of the higher plant pigments chlorophylls a and b. This review discusses antenna structures, photosynthetic properties and evolutionary relationships among these bacteria, with focus on the role of photosynthesis in their natural habitat. Most of the available information is obtained from studies on Prochlorothrix, the model organism of this group in laboratory studies. Our analysis yields a consensus from studies on two Prochlorophytes, Prochloron and Prochlorothrix, as to how the thylakoid membrane is organized. Lack of laboratory studies on an abundant third Prochlorophyte, Prochlorococcus, does not (yet) allow to include this species in the consensus. Overall, we propose that the structure of the light-harvesting complexes from Prochlorophytes is very different from those of chloroplast systems, and is evolutionarily very ancient. The light-harvesting apparatus is considered to maintain a strong structural and functional association with Photosystem I in both Prochlorothrix and Prochloron. Photosystem It in Prochlorothrix differs from other photosynthetic systems in structural and functional properties of both donor and acceptor sides of its reaction center. A demonstrated capacity for Photosystem I-dependent anoxygenic photosynthesis in Prochlorothrix may indicate that there is an increased dependence on cyclic photophosphorylation in these organisms. A description of the natural habitats of the Prochlorophytes has been employed as a jumping board for speculation on the role of the photosynthetic apparatus in occupying, proliferating and surviving in their ecological niches. Prochlorophytes seem to thrive in stable environments of low light, sufficient nitrogen supply and possibly the presence of essential organic solutes.

Effect of monoethanolamine on growth and biomass formation of rye and barley

Monoethanolamine (EA) applied to rye and barley as a foliar spray increased the biomass and grain yield formation of tillers (up to 14%) and promoted the growth of the basal stem parts (up to 17%). The increased production of tillers and the stimulated growth of basal internodes were associated with a higher nitrogen level in these plant parts. A sufficient nitrogen supply was an essential requirement for increasing the yield of tillers by EA.

Factors affecting saprophytic survival of six species of cereal foot-rot fungi

Previous work has shown that the effect of excess nitrogen in sharply curtailing saprophytic longevity of Cochliobolus sativus and Phialophora radicicola in colonized wheat straw buried in soil must be mediated by the activities of other soil micro-organisms. A higher level of soluble carbon nutrients was found in month-old cultures of C. sativus on wheat straw than in those of Fusarium roseum f. cerealis , but the difference in this respect between cultures of P. radicicola and F. roseum was smaller and not significant. This effect may therefore contribute to, but cannot account for, the adverse influence of nitrogen on saprophytic longevity of C. sativus and P. radicicola . From published data, twenty-six determinations, distributed amongst six species of cereal foot-rot fungi, were made of the period to median saprophytic survival (S50) under conditions where a sufficient supply of nitrogen had been made available. In two species, C. sativus and P. radicicola , abnormally low S50 values were associated with their negative response to nitrogen in longevity of survival. This finding suggests that these two species are displaced from their wheat-straw substrate, well before its ultimate exhaustion by competing soil micro-organisms. At the other extreme, the two species with the highest S50 values, F. roseum and Curvularia ramosa , are known to be vigorous competitive colonizers of fresh wheat straw. In general terms, saprophytic success in both colonization and survival seems to be associated with a high degree of tolerance to fungistatic growth products of microbial origin.

Studies on the nitrogen nutrition of tulips.

Effect of nitrogen supply and omission at the various stages of growth on the absorption of nutrients and on growth and yields of tulip were studied with 11.0g bulbs of‘William Pitt’in sand culture. Growth period was divided into the following five stages:I. Stage of root system development (Nov. 1-Mar. 14), II. Stage of earlier vegetative growth (Mar. 15-Apr. 19), III. Stage of later vegetative growth (Apr. 20-May 4), IV. Stage of bulb weight increase (May 5-May 31), and V. Stage of maturity (June 1-June 24).1. Growth of tops was remarkably reduced by the omission of nitrogen: leaves and flowers were considerably smaller and flowering was a little hastened than those of complete nutrition. Among the stages, stage II showed the greatest effects.2. Withering up of tops was accelerated by the omission of nitrogen at stage IV and delayed by the supply of nitrogen at this stage. The other stages had little effect on it.3. The effect of nitrogen on yields was the greatest at stage II and III, and much less at the earlier or later stages. Reduction of bulb weight due to nitrogen shortage was greater in lateral bulbs than in main bulbs.4. The omission of nitrogen at later stages indicated more marked reducing effects on the nitrogen content in bulbs than at earlier stages. And nitrogen supply at stage IV kept the content at its highest level, irrespective of the nitrogen supply before and after that stage.5. The nitrogen content of tops showed the same trend as that of bulbs; the only difference between them was that plants suffered from nitrogen dificiency for the period of vegetative growth failed to recover their nitrogen content in the tops by the nitrogen supply at stage IV.6. There were observed positive correlations between the contents of nitrogen and phosphorus in tops, bulbs and flowers. But when plants were grown under the condition of extreme deficiency of nitrogen, phosphorus concentration in each part of plants did not reduce so much as that of nitrogen.7. Potassium content in each part of plants showed no distinct differences among the treatments.8. The differentiation of flower bud in the harvested bulbs during the storage period was extremely delayed by the severe deficiency of nitrogen. The delay in other cases, however, could not be attributed either to bulb weight or final content of nitrogen, but to the nitrogen omission of stage I and/or II.9. There happened to be noted an unknown disease which caused brown necrotic spots on the surface of the outermost living scales. This disease prevailed when plants suffered from nitrogen deficiency during the period of their vegetative growth and received sufficient nitrogen supply at the stage of bulb weight increase. This fact suggested that the trouble might be of physiological nature.10. Among the studied five stages, the absorption of nitrogen was more active at stage II, III and IV. On the other hand, the efficiency of producing bulbs by the absorbed nitrogen was higher at stage I, II and III. It is considered, therefore, that stage II and III should be the most important period for nitrogen supply.

Effect of fertilizer on the withering or lower leaves in rice plants.

1) Time of withering of each leaf expressed by a particular index : "Seedling-age at the time of withering of a given leaf." 2) Rate of growth of seedlings as expressed by the length of time interval between the appearance of the successive leaves was accelerated by the supply of nitrogen fertilizer. The index "Seedling-age at the time of leaf withering" was also affected ; it became larger than the seedlings supplied little or no. 3) Only under the sufficient supply of nitrogen, phosphate fertilizer exert the effect of increase of the index.

Agricultural Chemistry 1

II. IT has been shown that the plant may receive abundance of x nitrogen, may produce abundance of chlorophyll, and may be subject to the influence of sufficient light, and yet not assimilate a due amount of carbon. On the other hand, it has been seen that the mineral constituents may be liberally provided, and yet, in the absence of a sufficient supply of nitrogen in an available condition, the deficiency in the assimilation of carbon will be still greater. In fact, assuming all the other necessary conditions to be provided, it was seen that the amount of carbon assimilated depended on the available supply of nitrogen.