Varying Nutrient Levels Research Articles

Biogeochemistry of manganese oxide coatings on pebble surfaces in the Kikukawa River System, Shizuoka, Japan

The biogeochemistry of Mn-oxide coatings formed over submerged pebble surfaces on the streambed of the Kikukawa river system has been investigated. Located in central Shizuoka, Japan, this system drains strongly acidified soils under tea plantations. Besides containing high amounts of Mn (up to 450 μg/cm 2), the coatings are capable of scavenging and accumulating other elements including Ba, Zn, Ni, Co, W, Mo and Sb. When suspensions of the coating material were incubated with 0.2 mM Mn 2+, the Mn(II) ion was microbially transformed into Mn-oxides. When the same suspensions were spread on agar plates containing acetate, yeast-extract, and 1.0 mM Mn 2+ (AY agar medium) both Mn-oxidizing bacteria and fungi appeared, indicating the existence of a diversity of Mn-oxidizing microorganisms in the system. Plate counts using two agar culture media with varied nutrient levels indicated that the ability of these microorganisms to oxidize Mn(II) was strongly dependent on nutrient supply. The relatively nutrient-poor AY agar medium was more conducive to microbial growth than the K 1 agar medium with a higher organic nutrient content. Concentrations of Mn dissolved in the stream waters did not correlate well with the amounts of solid Mn on submerged pebbles. Thus, factors other than dissolved Mn concentration (e.g., organic nutrient supply and pH) determined the ability of microorganisms to oxidize Mn in the streambeds. A survey of dissolved Mn in streams and water draining tea plantations combined with chemical analysis of Mn in the underlying soils indicate that the soils have been strongly acidified through excessive applications of N-fertilizers. As a result, Mn was leached from the soil column into the Kikukawa river system. Biogenic Mn-oxide coatings on streambeds can therefore serve as an indicator of soil acidification and metal leaching from soils of the corresponding watershed.

Growth Responses of Three New Zealand Northern Highbush Blueberry Cultivars (Vaccinium corymbosum) to Nutrient Availability.

Responsiveness of three New Zealand northern highbush blueberry cultivars (Vaccinlum corymbosum L.), 'Nui', 'Puru' and 'Reka' to three degrees of regulated nutrient availability was examined: 1) in the control treatment, no nutrient was added, 2) in the solid fertilizer treatment, a standard commercial fertilizer was applied at the start of the experiment, the release of nutrients being dependent on the properties of the fertilizer and environmental conditions, and 3) in the fertigation treatment, a dilute solution of readily available nutrients was supplied daily. Treatments were applied from mid-May 2001 up until plants were destructively harvested in mid-September 2001. For all three cultivars, accumulated dry matter in the fertigation treatment was 2 to 3 times that in the solid fertilizer treatment, whereas that in the control treatment was the least. 'Nui' had the lowest total dry matter levels, they were significantly higher in the fertigation treatment though because of increases in aboveground growth. The root system was unresponsive to the varying nutrient levels applied. 'Reka', the fastest, growing cultivar, had the most responsive root system, its dry weight increasing 2.9 fold in the fertigation compared to the solid fertilizer treatment, that of 'Puru' was intermediate. We concluded that there is potential to apply a finely regulated fertigation system to commercial blueberry production.

Seasonal variation in ecophysiological patterns in macroalgae from an Arctic fjord. II. Pigment accumulation and biochemical defence systems against high light stress

The content of photosynthetic pigments (chlorophyll a, biliproteins, carotenoids) and UV-absorbing mycosporine-like amino acids (MAAs), as well as the activity of reactive oxygen species scavenging enzymes (catalase, superoxide dismutase, glutathione reductase) was investigated in six macroalgal species with respect to the seasonal changes of the solar radiation regime and the macronutrient levels in the seawater of the Kongsfjord (Spitsbergen, Svalbard, Norway). The brown algae Laminaria saccharina, Saccorhiza dermatodea, Desmarestia aculeata; the red algae Palmaria palmata and Devaleraea ramentacea; and one green algal species, Monostroma aff. arcticum, were sampled from the same water depth, before, during and after the break-up of sea ice, first under clear and later under turbid water conditions in late winter, spring and summer 1998. In all species, chlorophyll a (chl a) and total carotenoid content were highest under the sea-ice cover, and decreased gradually upon the sea-ice break-up. Four species showed a subsequent recovery in chl a and total carotenoid concentration in parallel to increasing water turbidity and reduced light availability. In the two red algal species, total phycoerythrin and phycocyanin contents followed a similar trend. Coinciding with the increase in underwater radiation during the sea-ice break-up, both species exhibited a significant increase in the concentration of UV-absorbing MAAs, especially of shinorine and palythine. At the same time, the antioxidative activities of the enzymes superoxide dismutase and catalase in the green and red algae increased, while glutathione reductase activity decreased. Overall, the synthesis of UV-absorbing substances and the increase in the activity of the antioxidative systems in the open-water period imply an increased resistance to high underwater light conditions, including UV radiation. The seasonal changes in pigments and biochemical defence systems may additionally be related to variations in nutrient levels in the seawater. They also reflect the life strategy and the genetic adaptation of the seasonal development to the conditions in the Arctic.

Interactions among Nutrients, Periphyton, and Invertebrate and Vertebrate (Ascaphus truei) Grazers in Experimental Channels

Objectives of this study were to determine whether (1) stream algal biomass was nutrient limited, (2) stream herbivores could reduce algal biomass at different levels of productivity, and (3) a large vertebrate herbivore (Ascaphus truei) affected the abundance of insect grazers under different nutrient supply regimes. To address these objectives, we conducted a 2 3 2 factorial experiment to examine the effects of varying phosphate supply on periphyton biomass, insect grazers, and a tadpole grazer in 12 streamside experimental channels in southwestern Canada. We manipulated presence of tailed frog tadpoles (A. truei Stejneger) and varied nutrient levels using nutrient-diffusing pellets. We monitored periphyton biomass as ash-free dry mass (AFDM), insect grazer abundance, dissolved nutrients (NO 3 2 N and PO4 2 P) in water, and tadpole growth rates over 38 days. Dissolved nitrate and phosphate concentrations were temporally variable, and there were no statistical differences among treatments, but dissolved phosphate levels were 1.7 times greater in nutrientenriched channels (3.2 m gL 21) than in unenriched channels (1.7 m gL 21). Periphyton AFDM was significantly higher in channels with added nutrients, as was abundance of insect grazers, primarily Chironomidae and Ephemeroptera. Tadpoles in channels with nutrients had growth rates approximately four times higher than tadpoles in controls. Insect grazer abundance in channels with and without added nutrients was lower in the presence of tadpoles, and this reduction was greater in channels with nutrients. In contrast to other studies that have examined the impact of vertebrate herbivores on periphyton, tadpoles had no measurable effect on periphyton biomass. These data indicate periphyton and grazers were resource limited, as added nutrients increased periphyton biomass, as well as abundance (insect grazers) and biomass (tailed frog tadpoles) of herbivores.

Food consumption and growth of the juvenile sea urchin Strongylocentrotus intermedius

SUMMARY: Seasonal changes in food intake and digestion, and growth of the juvenile sea urchin Strongylocentrotus intermedius feeding on the large brown algae Sargassum confusum and Laminaria religiosa were studied during a rearing experiment. The food intake and the proportion of food digested were higher for sargasso than for kelp during July and October but lower during November and March, when only thalli without main or lateral branches of sargasso were consumed, resulting in a lower growth rate. The feed conversion efficiency for sargasso was higher during May and June, and lower during August and October, than that for kelp. However, the digestibility of both algae was inversely related to the feed conversion efficiency. It is considered that changes in digestibility and feed conversion efficiency are caused by interspecific differences and seasonal variations in nutrient levels.

Purine Stress in Crithidia: Adaptation of a Parasite to Environmental Stress

How parasitic protozoa survive varying nutrient levels is a key issue in parasitology. Here, Annette Gero explains how the Trypanosomatid Crithidia luciliae responds to purine stress by increasing the rates of transport of nucleosides and bases from the environment and by increasing the activity of the ectoenzyme 3′-nucleotidase (3′NTase), which breaks down external nucleotides so that they can be salvaged as nucleosides. The increase in activity of the purine transporters, and the 3′NTase activity is simultaneous with a general increase in the purine metabolic pathway, hence ensuring that purines are readily available to the parasite during purine stress.

Variation in Nutrient Levels of the Groundwater in the Upper Rhine Alluvial Forests as a Consequence of Hydrological Regime and Soil Texture

- ~~~~~~~~~~ Abstract. The Rhine in the French alluvial plain has been deprived of the main parts of its flooded areas. One of the consequences is the high level of nitrate in groundwater due to intensive agriculture except under forested areas. The purpose of this study is to show the role played by the forest ecosystem in influencing groundwater quality in relation to the hydrological regime, vegetation and soil characteristics. Phosphate and nitrogen levels in groundwater are compared in three forested sectors. Two are on a calcareous substrate, one of which is still flooded with summer high waters, whereas the other has not been flooded for 30 years. The third sector is on a decarbonated substrate which is flooded with high water in winter or early spring. In all the sectors phosphate, nitrate and ammonia are very low in the groundwater as compared to the surface water. Nitrate concentrations in groundwater differ widely between the three forested sites, whereas ammonia and phosphate remain relatively constant. Nitrate levels were the lowest in the sector with silty/clayey soils, whereas they were largely influenced in the loamy soil by hydrological conditions, whether flooded or not.

Adaptation to life at micromolar nutrient levels: the regulation of Escherichia coli glucose transport by endoinduction and cAMP.

Free-living bacteria are expert in adapting to variations in nutrient availability, often using an array of transport systems of different affinities to scavenge for particular substrates (multiport). This review concentrates on the regulation of expression of different transporters contributing to multiport in response to varying nutrient levels. A novel mechanism of controlling bacterial transport affinity under sugar limitation is described. In particular, switching from glucose-rich to glucose-limited conditions results in Escherichia coli orchestrating outer membrane changes as well as the induction of a periplasmic binding protein-dependent (ABC-type) transport system. The changes leading to the high affinity transport pathway are directed towards uptake of rapidly utilisable concentrations and are optimal close to 10-6 M medium glucose. High affinity transport is absent under both glucose-rich 'feast' and glucose-starved 'famine' conditions hence high affinity transporters are not simply repressed by excess nutrient. Rather, the improvement in glucose scavenging involves induction of genes in 2 distinct regulons (mgl/gal and mal/lamB) through synthesis of 2 different endogenous inducer molecules (galactose, maltotriose). Endoinducer levels are tightly controlled by extracellular glucose concentration at different glucose-limited growth rates. Aside from endoinducers, the elevated intracellular level of cAMP plays a role in induction of the high-affinity pathway but cAMP-mediated relief from catabolite repression is not itself sufficient for high affinity transport. In contrast to the repressive role of glucose when present at millimolar concentrations, micromolar glucose also leads to the induction of transport systems for other sugars, further broadening the scavenging potential of nutrient-limited bacteria for other substrates.

Comparison of Chromometer Readings and Sensory Evaluations on Plant Color and Quality

Plant nutrient treatment differences typically are identified through the use of plant height, leaf quantity, leaf area, and dry weight. Plant color differences may be determined quantitatively, by chromometer, or qualitatively, by sensory evaluations. Chromometer readings are easy an unbiased, however, overall plant quality must be determined by sensory evaluation. In this report, the two evaluation methods are compared. Poinsettias were grown in varying nutrient levels to flowering Chromometer readings were taken on one green leaf and one bract leaf of each flowering plant. Two sensory panels composed of commercial growers/retailers (or trained panel) and consumers, evaluated the mature plants into “Florist”, “Saleable”, or “Non-Saleable” grades. Chromometer and consumer evaluation results were comparable. The trained panel evaluations identified a more specific area of plan acceptance. The chromometer identified only color difference, whereas, the trained panel identified color and plant quality differences. The chromometer and trained panel evaluations, when used together, give complete understanding of treatment effects on quality.

Variations in nutrient levels in watermelon cultivars irrigated with saline water: Total ions

Abstract Few studies have been published on nutritional parameters in greenhouse cultivated watermelon despite the importance of this species in the human diet. It was therefore considered worthwhile to study some of the cultivars soon to become commercially available in Spain to determine which of them are best suited to cultivation in areas along the Mediterranean coast. All ten cultivars of Citrullus lanatus (Trunb) Mansfield studied were grown in polyethylene covered greenhouses. Four replications of each cultivar distributed in random blocks. Leaves were sampled every 15 days during one complete biological cycle to determine total macro‐ and micro‐nutrients. These data ere then related to productivity (fruit yield). The different cultivars presented marked differences in both macro‐ and micronutrient levels: total N in Perla‐Negra (Black Pearl) was twice that found in Tolerant, while total K in Resistent was double that in Candida. Total proteins also differed significantly between cultivarss as did ...

Influence of internal wave induced vertical mixing on ice algal production in a highly stratified sound

Field observations of tidally forced flow over a sill in a constricted region of the highly stratified Manitounuk Sound (Hudson Bay, Canada) are examined during the winter period under a complete landfast ice cover. Necessary conditions for high frequency internal wave generation over the semi-diurnal tidal cycle for both spring and neap tides are considered. Internal wave activity is found to occur more often on the downstream side of the constriction during flood. A fortnightly variation in upper layer salinity and nutrients is attributed to a similar periodicity in internal wave activity and upward salt transport across the pycnocline. The variation in nutrient levels within the upper layer and at the ice-water interface is thought to have a controlling effect on underice microalgal biomass downstream of the sill.

Vegetative Responses of Deschampsia flexuosa (L.) Trin. (Poaceae) Seedlings to Nitrogen Supply and Photosynthetically Active Radiation

1 When Deschampsia flexuosa (L.) Trin. was grown from seedlings in a glasshouse in summer, growth of the shoots declined (P < 0.001) as photosynthetically active radiation (PAR) and nitrogen concentration (N) decreased. These responses were largely a function of a reduction in numbers of tillers. PAR and N interacted positively at P < 0-001. 2 Individual tillers of D. flexuosa responded to reduced nitrogen and PAR (except at the lowest PAR level) by an increase in shoot dry weight, shoot length, leaf dry weight, leaf length, leaf number, leaf length ratio (=SLA) and leaf weight fraction. At the lowest PAR used, this trend was reversed. Leaf length ratio was the variable which showed the largest relative change and was the most consistent in its response to variation in PAR. 3 These results suggest that D. flexuosa has a greater capacity to respond morphologically to variation in nutrient levels than has previously been reported. The increase in the magnitude of tiller variables with decreasing nitrogen and PAR levels may be an adaptation which allows the species to be successful in shaded, low fertility

Effects of November–April grazing pressure on hill country pastures 3. Interrelationship with soil and pasture variation

Abstract Variations in soil moisture content, nutrient levels, and temperature were measured for a range of micro-sites located on a steep, north-facing hillside. Species distribution and plant responses to changing moisture conditions and different grazing treatments were related to these physical conditions. Soil nutrient levels (organic carbon; total, inorganic, and mineralised nitrogen; Olsen phosphorus; potassium) were highest in camp/old track areas reflecting nutrient transfer by grazing animals. Variation in nutrient level between other flat and sloping areas was low. Soil moisture holding capacities were similar for most areas, but sloping areas were consistently drier in the surface horizon (0–50 mm) because of less effective re-wetting compared with flatter areas. Maximum soil surface temperatures of 45–50°C were reached on clear days where low pasture cover existed on sloping areas. The effects of grazing treatments on ryegrass and browntop tiller number, white clover leaf number, and seedling establishment were similar across a wide range of micro-sites. However, pasture species content varied between micro-sites: ryegrass was dominant on camps and tracks; browntop increased with steepness of slope; white clover peaked on rolling and easy sloping areas; grass seedlings were most numerous on camps and tracks; and legume seedlings were most numerous on steeper slopes. Pasture type would appear to be determined more by nutrient fluxes (e.g., mineralisation rate, excreta return) and summer rewetting of the soil surface than by nutrient pool size and inherent water-holding capacity of the soil.

Dietary Intake and Nutritional Characteristics in Wild American Lobsters (Homarus americanus)

Nutrient and essential amino acid analyses of the stomach contents of wild adult American lobsters (Homarus americanus) collected from offshore and inshore populations indicated lobsters consumed varying nutrient levels according to their stage of molt. For example, soft-shell lobsters ate a higher level of mineral constituent. The location of the animal had no effect on the level of nutrient intake. The essential amino acid composition of the protein in the stomach remained the same throughout the molt cycle, but indicated a change in protein source with the location of the animal. The relationship between crude protein and gross energy was constant suggesting its importance in the nutrition of the lobster. Based on this study, we recommend a basal level of nutrient constituents for ration formulation. Key words: American lobster, natural intake, dietary formulation

Estimated Responses of Lake Ontario Phytoplankton Biomass to Varying Nutrient Levels

A series of simulations of the response of the open lake region of Lake Ontario to various levels of nutrient input is described using a simplified dynamic model of phytoplankton-nutrient interactions in a vertically segmented lake. The analysis of the simulations indicates the importance of the overall loss rates of nutrient. Under an hypothesized, but reasonable, set of model parameters, the simulations indicate that the present observed open lake phytoplankton biomass of Lake Ontario does not appear to be in equilibrium with the present input nutrient load. For an assumed equilibrium condition, the simulations indicate that reductions in phosphorus load will be accompanied by reductions in biomass. A “pastoral” simulation using load estimates consistent with the conditions prior to man's intensive activity indicates that spring phytoplankton levels were 30%-70% of present levels depending upon the kinetic assumptions. Analysis of lake response to the U.S.-Canada Water Quality Agreement loads using three kinetic assumptions (optimistic, reasonable, pessimistic) indicates a range from 25% decrease to 80% increase in peak phytoplankton over present levels. For an implementation period of 10 years, a load reduction rate of about 1-1.5 metric tons phosphorus/day per year appears to be a sound objective to maintain or reduce present phytoplankton levels.

Genotypic variation in traditional rice varieties for chlorophyll content, SPAD value and nitrogen use efficiency

Nitrogen % in both straw and grain, nitrogen uptake by straw and grain, total nitrogen uptake and physiological nitrogen use efficiency (PNUE) showed significant differences due to variable nutrient levels at maturity in traditional rice varieties. PNUE ranges from 40.58 to 49.88 (kg/kg N). Significantly higher PNUE without addition of nitrogen (Zero N) indicated the ability of utilization of the native nitrogen by traditional varieties. Traditional varieties produced 49.88 kg grain by the utilization of zero nitrogen treatment followed by 45.93 kg grain in cowdung (10 t/ha), while 40.58 kg grain by the application of 80 kg/ha nitrogen. The higher PNUE in zero nitrogen treatment confirmed the ability of producing similar yield level compared to added nitrogen treatment. Bashful chikon, might be important due to higher nitrogen content and Badiruzzman considered due to more straw nitrogen (0.71%). Barud also showed excellence with regards to PNUE and total nitrogen uptake. Leaf chlorophyll profile showed a very consistent level in all the varieties except Laichi. Soil plant analysis development (SPAD) value ranged from 34.06 to 41.69, while leaf nitrogen ranged from 2.99 to 3.49 %. SPAD value recorded over time showed four distinct patterns during 15 to 90 DAT. Key Words: Genotypic variation, rice varieties, SPAD value, nitrogen use efficiency. DOI: 10.3329/bjar.v34i3.3977 Bangladesh J. Agril. Res. 34(3) : 505-515, September 2009

The effect of varied nutrient levels on the concentration and distribution of manganese within the potato plant

1. Potato plants were grown in sand culture with varying levels of iron, potassium, phosphorus and calcium carbonate and an adequate supply of manganese. The concentration and distribution of manganese in various parts of the plant were examined at intervals throughout the growing season. 2. Increased iron supply decreased the concentration of manganese of the laminae and stems and petioles but increased that of the roots; iron application also decreased the uptake of manganese by the plant. 3. Increased potassium supply increased the concentration of manganese in the stems and petioles and also in the laminae late in the season after having caused a decrease at the beginning of the growth period. Potassium level had no marked effect on manganese uptake. 4. Increased phosphorus supply decreased the uptake of manganese by the plant and decreased its concentration in the laminae, stems and petioles and roots. 5. The addition of calcium carbonate decreased the concentration of manganese found in the laminae and tubers, especially at iron deficiency levels. 6. Extra potassium or phosphorus generally reduced the proportion of manganese retained in the roots whereas iron addition impeded the translocation of manganese to the shoots and caused an accumulation in the roots. 7. Increased potassium supply increased the proportion of manganese in the newly formed tubers and in the stems and petioles whereas phosphoru increased that of the laminae. 8. It is suggested that one of the functions of potassium was to increase the mobility of manganese within the plant.