Sr. Tang et al., Heavy-metal uptake by metal-tolerant Elsholtzia haichowensis and Commelinacommunis from China, COMM SOIL S, 32(5-6), 2001, pp. 895-905
Elsholtzia haichowensis Sun and Commelina communis L. are the most widely d
istributed heavy-metal-tolerant plants in the areas along the middle and lo
wer streams of the Yangtze River, China. Both plant species were grown in p
ot trials involving three different treatments containing 3-12 mg kg(-1) ca
dmium (Cd), 37-140 mg kg(-1) copper (Cu), 30-101 mg kg(-1) chromium (Cr), <
3-9 mg kg(-1) nickel (Ni), 66-224 mg kg(-1) lead (Pb), and 1,000-2,850 mg k
g(-1) zinc (Zn). Hydroponic trials were also conducted using Cd, Cu, and Zn
only. Both species accumulated much higher concentrations (by a factor of
about ten) of copper and other heavy metals in the roots than in the shoots
, following a typical pattern of metal-excluder plants. The metal concentra
tions in the plant tissues, especially the roots, of E. haichowensis and C.
communis were positively correlated to the metal concentrations in the gro
wth media. With increasing heavy metal concentrations in the root media, th
e shoot biomass yields of E. haichowensis increased, but the root yields sh
owed no significant variation. Shoot or root dry biomass of C. communis inc
reased in the case of the pot trials but decreased in the hydroponic cultur
e fi om the low metal to high metal treatments. The results suggest that E.
haichowensis may be a better biogeochemical indicator than C. communis for
ore exploration and both may also be used fur phytostabilization of toxic
mine spoils because of their tolerance to heavy metal. It is pro posed that
although either roots or shoots could be used for biogeochemical prospecti
ng, shoot sampling would be easier and more cost-effective.