Phytoremediation of Pentachlorophenol in the Crested Wheatgrass (Agropyron cristatum × desertorum) Rhizosphere

Abstract

Pentachlorophenol (PCP) is a widespread, highly toxic contaminant of soil and water that is generally recalcitrant to microbial breakdown and thus may be considered a good candidate for phytoremediation. PCP toxicity and rates of mineralization were compared in crested wheatgrass seedlings that were either sterile or rootinoculated with microbial consortia derived from soil at a PCP-contaminated site. Inoculated seedlings were more tolerant to PCP and mineralized threefold more 14 C-PCP than sterile seedlings. Only 10% of the recovered radioactivity from sterile seedlings represented mineralized PCP, indicating that rhizosphere microorganisms are primarily responsible for PCP mineralization. The levels of PCP degradation exhibited by several microbial consortia and isolates in liquid culture were not correlated with their ability to protect crested wheatgrass seedlings from PCP toxicity. Most probable number estimates showed that the presence of crested wheatgrass root exudates enhanced the number of PCP-degrading microorganisms by 100-fold in liquid culture, indicating that exudate components provide some nutritive benefit, possibly as PCP co-metabolites. A close association of plants and rhizosphere microorganisms appears to be necessary for crested wheatgrass survival in PCPcontaminated soil, although understanding the molecular details of this association requires further research.

Turfgrass Benefits and Issues

“…'Hycrest' crested wheatgrass [Agropyron desertorum (Fischer ex Link) Schultes] accelerated the degradation of pentachlorophenol (PCP), a compound used to treat lumber to prevent rot, in contaminated soil with 36% of the PCP absorbed by the plants and 22% mineralized (Ferro et al, 1994). Subsequent research found that microbes in the rhizosphere were responsible for mineralizing the PCP (Miller and Dyer, 2002). While the specifi c microbes were not identifi ed, experiments indicated that root exudates from the wheatgrass helped recruit PCP-degrading microbes and served as co-metabolites to enhance PCP degradation.…”

Chlorophenols induce lipid peroxidation and change antioxidant parameters in the leaves of wheat (Triticum aestivum L.)

“…Wheatgrass removed PCP from soil (Miller and Dyer, 2002) and rice showed the ability to remove 2,4-DCP from nutrient solutions (Su and Zhu, 2006). It has also been shown that wheat is able to take up 2,4-DCP from aqueous solutions with an efficiency of almost 20%.…”

Chloroguaiacols Change Some Antioxidative Parameters and Affect the Activity of Glutathione S-transferase in the Leaves of Reed Canary Grass (Phalaris arudinacea)

“…Wheatgrass and ryegrass removed pentachlorophenol from soil (Miller and Dyer 2002;He et al 2005). Chlorella and rice showed the ability to remove 2,4-dichloropenol from nutrient solutions (Scragg et al 2003;Su and Zhu 2006).…”