EFFECT OF NUTRIENT CONCENTRATION ON

Only two decades ago researchers started to study the effect of nutrient concentration on cell growth and metabolism systematically and the effect of pro-... 

Fig. 7.4. Differential effect of nutrient supply on biomass and cord development in Serpula lacrymans. The fungus was inoculated centrally on uniform defined agar media in a factorial experiment with 5,10, 20, 40 and 80g/l sucrose and 1.5, 3, 6 and 12.5 g/1 sodium aspartate. Biomass was measured as oven dry weight at 8 weeks, cords were counted crossing a circular transect 3 cm from the inoculum disc. Left to right C/N ratio of each of the twenty combinations of carbon and nitrogen concentration biomass cord development. (Adapted from Watkinson, 1975).

FIGURE 5.54 Effect of phosphorus concentrations on decomposition of organic matter with different nutrient ratios. (Adapted from DeBusk and Reddy, 1998.)... 

Rubin HE, M Alexander (1983) Effect of nutrients on the rates of mineralization of trace concentrations of phenol and p-nitrophenol. Environ Sci Technol 17 104-107. 

Extensive studies on the effect of substrate concentration and on the bioavailability of the substrate to the appropriate microorganisms have employed samples of natural lake water supplemented with suitable nutrients. There are few additional details that need to be added since the experimental methods are straightforward and present no particular difficulties. Considerable use has also been made of a comparable methodology to determine the fate of agrochemicals in the terrestrial environment. 

The ability to change and control the composition of the nutrient solution and the relatively small size of the microcosms used enables manipulation of environmental variables and time-course studies of rhizodeposition to be made relatively easily. The influence of nutrient availability, mechanical impedance, pH, water availability, temperature, anoxia, light intensity, CO2 concentration, and microorganisms have all been examined within a range of plant species (9). A few examples to illustrate the continued interest in examining the effect of such variables on rhizodeposition in nutrient culture are given in Table 1. 

Mitchell L.G., Grant C.A., Racz G.J. Effect of nitrogen application on concentration of cadmium and nutrient ions in soil solution and in durum wheat. Can J Soil Sci 2000 80 107-115. 

Experiment 1. Effects of volatile allelochemicals on development of pollen tubes. In this experiment, volatile and liquid excretions from plants with pesticidic properties were tested (Table 3). The development of pollen tubes depend on the concentration and the distance from the object glass with microspores moistened with nutrient medium vapors of lavender oil (active matter) depress the process as well as red pepper, but garlic not. Water extracts of garlic were more effective. 

The flow rate and concentration of wastewater do not remain constant but vary during the course of the day and are also dependent on the time of year. If the flow rate is too high, loss of micro-organisms by washout may occur in secondary treatment processes. If the flow rate is too low, then the lack of nutrients will lead to a reduction of the micro-organism population. Wastewaters entering a treatment plant usually flow first into an equalisation basin, so that the flow rate out of the basin is maintained constant, or between prescribed limits, to protect the subsequent processes. The equalisation tank also reduces the effect of toxic shocks on the biological processes within the main treatment plant. 

Matrix effects in the analysis of nutrients in seawater are caused by differences in background electrolyte composition and concentration (salinity) between the standard solutions and samples. This effect causes several methodological difficulties. First, the effect of ionic strength on the kinetics of colorimetric reactions results in color intensity changes with matrix composition and electrolyte concentration. In practice, analytical sensitivity depends upon the actual sample matrix. This effect is most serious in silicate analysis using the molybdenum blue method. Second, matrix differences can also cause refractive index interference in automated continuous flow analysis, the most popular technique for routine nutrient measurement. To deal with these matrix effects, seawater of... 

Stimulation of active H+ extrusion from roots (Cesco, 1995 Pinton et al., 1997 Table 9.1) and transmembrane potential hyperpolarization (Slesak and Jurek, 1988) indicated the involvement of the PM H+-ATPase in the increased nutrient uptake generally observed in the presence of humic substances. Direct proof of an interaction between humic molecules and the PM H+-ATPase has been obtained by Vara-nini et al. (1993), who demonstrated that low-molecular-weight (<5kDa) humic molecules at concentrations compatible with those present in the rhizosphere can stimulate the phospho-hydrolytic activity of this enzyme in isolated PM vesicles (Table 9.1). Further proof of the action of humic molecules on PM FT-ATPase activity and on nutrient uptake mechanisms was obtained when studying the effect of these molecules on NO3 uptake. Transport of this nutrient is a substrate-inducible process and involves FT co-transport. At higher uptake rates, the levels and activity of root PM FT-ATPase increased (Santi et al., 1995). The short-term (4h) contact... 

Changes in environmental factors, including levels of grazing, salinity, nutrients, visible light, UV light and desiccation, can affect concentrations of chemical defenses in marine macroalgae. Work conducted on terrestrial and marine plants suggests that the direct effects of environmental factors on chemical defense concentrations are manifested in three ways ... 

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