Plant metal induction

Table 6-1. Metal induction of peroxidase in different organs of higher plant species (after Van Assche and Clijsters, 1990b, adapted).

Induction heating equipment installations can require significant investment in electric power components as well as the work handling equipment made necessary by the process. These costs can be offset by savings in plant space, reduction in metal loss, precise control of product temperature, and reduced in-process inventory. A typical continuous induction heating line consumes about 360 kW h/t heating carbon steel bars to 1230°C. 

Some years ago, the process, shown in Fig. 14.20, was suggested as a centrally located plant for treatment of metal-containing waste in Sweden. The operation is based on the use of a pyrometallurgical induction converter and hydrometallurgical AmMAR process technology. 

Further, there are dry processes in w/hich degassing in vacuum is the actual technical process. These include work in induction- and arc furnaces, steel degassing plants, and plants for the manufacture of pure metals and electron tubes. 

The metallothioneins have been found in several vertebrate species and in marine invertebrates.1452 Prinz and Weser purified a copper-containing metallothionein from Saccharomyces cerevisiae.1453 Another copper-binding protein was isolated from Neurospora crassa.1452 The first unequivocal demonstration of a metallothionein in a vascular plant was recently reported.1455 The amount of metallothionein in different species and tissues is variable. The concentration has been reported to increase up to 40-fold by the induction of its biosynthesis by certain metals such as cadmium or zinc. In new-born rat liver (one to four days old) the concentration of Zn- and Cu-metallothionein is 20 times that in 70-day-old adult rats.1456 There are several recent reports and reviews in this active area.1243,1467a k... 

Enzyme induction and/or isoenzyme variation have been used to characterise widely different phenomena. These enzymatic parameters were shown to be useful criteria for monitoring air pollution (Keller, 1974 Fliickiger et al., 1978 Rabe and Kreeb, 1979), for ecogenetic characterisation of plant populations (Verkleij et al, 1980 Triest, 1991), for the study of callus tissue differentiation (Coppens and Gillis, 1987) and plant development and differentiation (Scandalios, 1974). The evaluation of phytotoxicity of metal-polluted soils and other substrates can also be realised by enzymatic parameters. 

To increase production and facilitate isolation, plant cells have been immobilised on various matrices such as polyurethane foam and calcium alginate gel beads,24 while elicitation (i.e. the induction of a defence response) is generally critical for the production of secondary metabolites. The rationale for the use of elicitors is that plants produce secondary metabolites as part of a defence response to stress, either biotic (pathogen infection) or abiotic (ultraviolet, toxic heavy metals and rare earth ions). Jasmonic acid plays a crucial role in plant stress responses and, along with fungal polysaccharides and heavy metals, is the most widely employed elicitor in plant tissue cultures.30... 

Official Methods of Analysis of AOAC International, 17th edn. Rev 1, AOAC International, Gaithersburg, MD, USA, Official Method 985.01. Metals and Other Elements in Plants and Pet Foods - Inductively Coupled Plasma Emission Spectroscopic Method (2002)... 

In plants, two kinds of metal-binding peptides or proteins are synthesized. Plant metallothioneins are inducible cysteine-rich entities very like those found in animals. Differential expression (induction) of metallothionein genes can be due to both variation of external heavy metal concentrations and the influence of various environmental factors. The principle role of plant metallothioneins seems to be in homeostasis rather than in metal detoxification. Plants are also known to have so-called phytochelatins, which are non-protein thiols specifically induced upon exposure to heavy metals. A close positive relationship between the concentrations of cadmium and phytochelatins in the plant shoot material has been observed and linked to the degree of growth inhibition (Keltjens and Van Beu-sichem, 1998). These observations make the use of phytochelatins promising for the assessment of heavy metal effect on plants. 

---