Chaney, R.L. 1983. Plant uptake of inorganic waste constituents. pp 50-76. In J.F. Parr, P.B. Marsh and J.M. Kla (eds.) Land Treatment of Hazardous Wastes. Noyes Data Corp., Park Ridge, NJ.
	/REF-VER/Copy [Hyperaccumulators: Chaney et al.] REVIEW. Summarizes information on metal uptake and tolerance by plants in relation to soil metals concentrations and other soil properties such as pH and OC. Reviewed metal hyperaccumulator crops, as reported by Brooks et al. in 1977. First published description of using hyperaccumulator plants to phyto-remediate metal contaminated soils, considering Ni removal by corn vs. Alyssum. Initially in USDA report on Land Treatment of Hazardous Wastes, to EPA, 1980.
	From the paper: starting on page 62:
	The Ni hyperaccumulator case-- Information about Ni uptake and translocation will be noted here as an example. Research on Ni hyperaccumulators has progressed rapidly during the last 3 years. Enough information is available to consider different aspects of this example.
	Crop plants tolerate only 50-100 ppm foliar Ni. A few crops are much more tolerant of soil Ni (corn, smooth bromegrass) than others which are very sensitive to Ni in acid soils (orchardgrass, peanut, oat). In Ni rich acid soils, nearly every crop plant suffers Ni-induced Fe-deficiency (Roth, Wallihan and Sharpless, 1971; Hunter and Vergnano, 1952; Halstead, Finn and MacLean, 1969; Chaney et al., 1987; Anderson, Meyer and Mayer, 1973; Patterson, 1971; Mitchell, Bingham and Page, 1978; Crooke, 1956; Nicholas, Lloyd-Jones and Fisher, 1957).
	Ni-tolerant ecotypes of grasses were discovered on Ni-rich soils in several parts of the world. Only Alyssum bertolonii was thought to be an accumulator. Then Wild (1970; 1971) reported both types of Ni tolerance: Perennial shrubs which accumulated high levels of Ni, and tolerant grasses which did not translocate Ni to shoots.
	Lyon et al. (1968; 1970; 1971) reported Ni and Cr levels in some natural vegetation of New Zealand serpentine soil regions. Several had somewhat high Ni levels. Wild (1970, 1971) described Dicoma nicoliffera which hyperaccumulated Ni. Cole (1973) noted an Australian Ni-hyperaccumulator; Severne and Brooks (1972) found the same species with 1% Ni in dry leaves, and 23% Ni in leaf ash; both Ni and Co were accumulated. These results suggested that plants might eventually be used to mine metals from the soil, and research was intensified.
	Brooks, Lee and Jaffre (1974) found other Ni-accumulators. Subsequently, Jaffre et al. (1976) reported on Serbertia acuminata. The common name is "blue sap" after a blue-green latex excreted when the tree is cut. The saps contains 25.7% Ni (dry weight), but is comparatively low in Co. The plant discriminated between Ni and Co. Subsequently Brooks and his colleagues identified the Ni compound present in the sap as Ni(Ni citrate) (Lee et al., 1977, 1978; Kersten et al., 1980). Many Ni-hyperaccumulators appear to use chelation with citrate to protect the foliage from Ni toxicity. Some use malate and malonate rather than citrate. Brooks et al. (1977, 1979) then worked with herbarium specimens of plants from areas with Ni-rich soils to identify other Ni-hyperaccumulators within several genera. Alyssum contained 45 hyperaccumulators out of 168 recognized species. The conducted pot experiments with normal and hyperaccumulator species and found normal species suffered phytotoxicity with 50-300 ppm foliar Ni while hyperaccumulators grew well with as much as 19,000 ppm foliar Ni (Brooks et al., 1979; Morrison et al., 1980). If leaves are 1% Ni, leaf ash could be about 25% Ni, a rich ore. If plants can separate Co and Ni, their ash would be even more valuable.
	Such extreme hyperaccumulators are available for Ni, Zn, Cu, Co, and Cr. Although far too little is presently known about these plants to pan their use for phyto-extraction of heavy metals from soils, this concept is useful to consider if even this best case for removal might be helpful in managing land treatment sites.
	Let us presume that two crops could be grown on a land treatment site rich in Ni. One is the Ni-tolerant corn which would suffer yield reduction at 100 ppm, while the other is a Ni-hyperaccumulator which accumulates 10,000 ppm before yield reduction is clear. The site can be managed to grow each crop at the pH level which just causes visual symptoms of phytotoxicity. The soil contains 1000 ppm Ni in the surface 15 cm. Corn yields 10 dry Mt silage/ha which contains 100 ppm Ni; the whole crop contains 1 kg Ni/ha, 0.05% of the total soil Ni. The hyperaccumulator yields only 5 Mt/ha dry shoots/ha, containing 10,000 ppm Ni. This crop contains 50 kg Ni/ha, and removes 2.5% of the 2000 kg Ni/ha-15 cm surface soil. Upon ashing, the corn ash is only 0.25% Ni, too low to be of economic use, while the hyperaccumulator ash is 25% Ni, a rich ore. Theoretically, by repeatedly cropping the site and removing 50 kg/yr, one could remove half the total soil Ni in 20 years.
	This scenario suggests that research might prove useful on working out agronomic systems for metal hyperaccumulators. Until the recent research was conducted by Brooks and colleagues, this discipline appeared to have only academic interest, or possible application in biogeochemical prospecting. TRLC@S