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11 Flax (Linum usitatissimum L.) and Hemp (Cannabis sativa L.)... 209

strains) or fibre content/composition (fibre strains), but not on mineral composi-
tion of hemp plants (viz. monograph edited by Ranalli 1999). First reports dealing
with heavy metals uptake/accumulation by hemp were concentrated on the
agrotechnological treatments (e.g. fertilisation, liming) affecting heavy metal
phytoavailability (Jurkowska et al. 1990, 1992; Jasiewicz 1991) and toxic effect
of metal elements on hemp plants (Gorlach and Gambus ´ 1992; Gorlach 1994).
These studies were immediately followed by the idea for the potential use of this
crop to clean industrially polluted soil with possible use of contaminated biomass
for industrial products (Mankowski et al. 1994; Baraniecki et al. 1995). Recently,
several reports have seriously studied hemp phytoextraction potential of heavy
metals (Lo ¨ser et al. 2002; Linger et al. 2002; Angelova et al. 2004; Antonkiewicz
et al. 2004; Kos and Les ˇtan 2004). To date, ca. 30 journal papers (mostly national
journals), book chapters or conference abstracts have been published dealing with
hemp and heavy metals. Main portion of data includes Cd, Pb, Cu, Zn, Ni and Cr
and they are summarised in Table 11.4.

11.5 Heavy Metal Phytoextraction by Flax and Hemp

11.5.1 Genetic Variation in Uptake, Translocation and
Accumulation of Heavy Metals

Both flax and hemp do not represent HMs-hyperaccumulators—this fact may be
compensated by production of high above-ground biomass (particularly in hemp;
viz. Table 11.1). Nevertheless, the choice of genotypes/lines/varieties with higher
accumulation of particular metal elements (Cd, Pb, Zn, Ni) would be beneficial for
the final impact of phytoextraction technology. Unfortunately, no breeding work in
flax and hemp has been done for a trait “high/improved HMs uptake and accumu-
lation” previously; the situation was just opposite—the selection was carried out for
lines with low HMs (mainly Cd) seed content (Cieslinski et al. 1996; Li et al. 1997;
Hocking and McLaughlin 2000; Eboh and Thomas 2005; Korkmaz et al. 2010)as
related to hygienic aspect. Thus, the knowledge of genetic/phenotype differences in
accumulation (and mainly transport to above-ground plant parts) and tolerance to
particular HM elements is crucial for formulation of efficient phytoextraction
technology. The candidate genotypes may be found/screened either within com-
mercial varieties or germplasm resources. In fact, flax represents the only species
within fibre crops with some available data on genotype screening for heavy metal
tolerance/accumulation. Most of papers dealing with fibre crops and heavy metals
reported experiments usually with one or two genotypes of particular crop, and
thus, natural genetic variation in this trait remains still unknown.
The existence of genotype differences in the uptake and distribution of heavy
metals by flax plants was confirmed unequivocally by many authors (Marquard
et al. 1990; Marquard and Bo ¨hm 1992; Helal et al. 1991;Bo ¨hm et al. 1992;