Uptake in plants

Additional removal of BOD5 and T-N could be obtained at the anaerobic/anoxic tank of the constructed wetland. About 57 % of the ranaining BOD5 was removed at the anaerobic/anoxic tank. More than 74 % of the remaining T-N was denitrified, and the average concentration of T-N at the final effluent was 6.9 mg/L. The maximum available capacity for nutrient uptake in plants was far less (of the order of 5 %) than the loading rate of nutrients to the constructed wetland. 

N. M. Crawford and A. D. M. Glass, Molecular and physiological aspects of nitrate uptake in plants. Trends Plant Sci. 3 389 (1998). 

W. Schmidt, Mechanisms and regulation of reduction-based iron uptake in plants. New Phytol. I4I (1999). 

As we saw in Chapter 7, zinc uptake in plants involves proteins of the ZIP family, some of which are root specific while others are found in both roots and shoots. The transport of zinc from the cytosol in many organisms is often associated with members of the cation diffusion facility (CDF) family. Although there are 12 predicted family members in Arabidopsis, only one, MTP1, has been characterized, which seems to function in the transport of Zn into the vacuole. Two members of the heavy metal ATPase (HMA) family, HMA2 and HMA4, have been shown to function in the transport of zinc out of the cells across the plasma membrane. 

Reid RJ, Brookes JD, Tester MA, Smith FA. 1996. The mechanism of zinc uptake in plants-Characterisation of the low-affinity system. Planta 198 39-45. 

York and New England are devoid of fish due to the effects of acid rain. Indirect effects of the low pH values associated with acid rain also affect organisms. As noted in Table 13.1, one of the properties of an acid is the ability to dissolve certain metals. This has a profound effect on soil subjected to acid rain. Acid rain can mobilize metal ions such as aluminum, iron, and manganese in the basin surrounding a lake. This not only depletes the soil of these cations disrupting nutrient uptake in plants, but also introduces toxic metals into the aquatic system. 

Most importantly, the radionuclide and the stable nuclide must undergo isotopic exchange. In practice, this means that the tracer and the stable atom must be in the same redox state. By heating or using redox cycles, the experimenter must assure this to be true. Anomalous experimental results have frequently been traceable to the chemical form of the administered radiotracer. Since reactor production of radionuclides often results in side reactions (see Chapter 10), various oxidation states may be present when the sample is produced. In one case involving phosphate-32P uptake in plants, the unexpected experimental results were explained by the fact that a large percentage of the tracer dose was actually in the form of phosphite-32P. 

The study of mechanisms of metal uptake in plants often requires knowledge of the specific compounds and complexes in which the metals are present in... 

Francis, C. W. (1978). Radiostrontium movement in soils and uptake in plant. Technical Information Center, US Dept, of Energy. 

This chapter begins at the bottom of the agricultural food chain, looking at the uptake of PCDD/Fs in plants from soil. The second section deals with the uptake in plants from the atmosphere. The attention then switches to the next link in the food chain, and the transfer from plants and soil to livestock and animal food products is examined. This is followed by a discussion of uptake in humans from food and in infants from mothers milk. The chapter concludes with a short summary, an overall perspective on bioaccumulation in the agricultural food chain, and a brief reference to some consequences of this knowledge for risk assessment. 

A much slower transport process which catalyzes the net uptake of ATP has been demonstrated in liver [42,43] and heart mitochondria [44,45], and shown to be physiologically important in neonatal liver mitochondria [46,47]. The transporter s activity may be affected by hormones since it has been shown that glucagon treatment increases the total nucleotide content of subsequently isolated liver mitochondria [48]. Although initially thought to be due to rather nonspecific leakiness of mitochondrial membranes or unidirectional transport on the adenine nucleotide carrier, its lack of sensitivity to membrane potential, and its almost absolute dependence on the presence of Mg and phosphate suggest that the observed activity is due to a separate transporter [42]. Net nucleotide uptake in plant mitochondria is much more marked but has a similar dependence on Mg " and phosphate in the media [49]. 

There was a moderate adsorption of Al to Fe plaque, and this resulted in reduced Al uptake in plant tissue of Phragmites (Batty et al., 2002). Copper is concentrated in Fe plaque but will preferentially adsorb to Mn if Mn is present in the plaque (St-Cyr and Crowder, 1990 Ye et al., 2001). The sequestration of Cu in the root plaque appears to reduce uptake of Cu by the plant. However, as Cu concentrations build up on the Fe plaque, the amount of Cu transported into the plant tissue can increase (Ye et al., 2001). Zinc can also be concentrated in Fe plaque. For Typha, this effect is more pronounced in the field than in artificial laboratory microcosms (Ye et al., 1998). Several reports have shown... 

Metal uptake in plants can be enhansed by the application of soil and foliar amandments. Amendments consist of proprietary combinations of metal solubilizing agents, chelates and organic acids that increase plant availability and uptake of soil contaminant concentrations. The amendments are applied as a foliar or surface spray or through the irrigation system. 

Nitrogenous fertilizers have an acidifying effect and possibly enhance the cation exchange capacity of the roots. The application of those fertilizers to soil is thought to lead to an increased zinc uptake in plants (Lindsay 1972, Mortvedt and Gilkes 1993). 

The development of the following three models was based on the results of Puschenreiter et al. (2005), which suggest that root exudation and replenishment of soluble Ni from less available sources can be key processes governing metal uptake in plants. 

Table 29.2.3.6 shows the physicochemical properties of thiamethoxam (13). Its properties favor rapid and efficient uptake in plants and xylem transport [37, 53]. Through this systemic activity all plant parts situated acropetally from the application site can be protected. 

Ureases [27] Niai)-Niai) Hydrolysis of urea Treatment of bacterial infections, regulation of nitrogen uptake in plants... 

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