The impact of copper pollution on barnyard grass populations.

Abstract

Barnyard grass strains, Echinochloa oryzicola, 4X and E. crus-galli, 6X, (progenies of single plants) collected from Cu-polluted (25-310 ppm) and control (1-18 ppm) fields were tested for Cu tolerance and other characters. Cu tolerance was evaluated by the ratio of performance in Cu-treated plot to that in control (no Cu) plot, mainly in gravel culture and partly in water culture. The 4X species were more tolerant than the 6X species. The 6X strains resembling the 4X species morphologically had higher tolerance than typical 6X strains. In both species the populations in polluted fields showed a higher frequency of tolerant plants or a higher mean tolerance than those in control fields. The populations were polymorphic not only morphologically, but also in Cu tolerance. There were tolerant plants in normal fields and sensitive plants in polluted fields. The tolerant plants generally had small sized organs and were inferior in performance when tested in normal conditions. They were also inferior in competitive ability. The tolerant strains showed a lower Cu content in the leaves and stems than normal strains in the Cu-treated plot of gravel culture. The data were largely comparable with those reported by British workers in perennial grass species growing on strongly polluted sites, although the level of Cu pollution in Japanese rice fields was much lower.