Biotransfer Possibilities of Selenium from Plants Used in Phytoremediation

Abstract

We are investigating the biotransfer of accumulated Se by the plant in several phytoremediation systems. In study I, we evaluated the biotransfer of Se from Indian mustard, a Brassica species, to the insect-cabbage looper (Trichoplusia ni); mortality, deterrence, and biomagnification of Se were examined. We determined that feeding behavior of food chain consumers was affected not only by the plant concentration of Se, but also by the mobility of the insects and choice of feed available. In study II, we examined the survival and development of beet armyworm (Spodoptera exigua) fed Se-enriched plant tissues from different lines of saltbush (Atriplex spp.) After feeding on lines of saltbush that produced high biomass and accumulated high concentrations of Se, insect growth and survival was reduced. In studies III, IV, and V, lambs, dairy cows, and rabbits were fed Se-enriched Brassica and Medicago (alfalfa) plants as part of their feed ration. None of the tested animals exhibited any Se toxicity symptoms, but they had increased levels of Se in most tissues sampled (e.g., organs, blood, urine, feces), excluding milk. In study VI, we evaluated biotransfer of Se from broccoli to rats to determine efficacy of Se for reducing colon cancer. We found that Se-enriched plant material was more effective than inorganic sources of Se for preventing precancerous colon lesions. Results from all studies clearly show that Se absorbed by plants can be transferred biologically in an intentional or unintentional manner to insects and animals.

Evaluation of Atriplex lines for selenium accumulation, salt tolerance and suitability for a key agricultural insect pest

“…The presence of Se in irrigation water increased plant resistance to the insect tested in this model system, which is in agreement with the data generated for Indian mustard (Ban˜uelos et al, 1999). This suggests that Se may enhance plant resistance to the beet armyworm, but the literature is too limited to allow definitive generalizations.…”

“…Possible biotransfer of Se from plants to insects may not only have consequences for the pest insects , but also for vertebrates and invertebrates that feed on insect herbivores (Wu et al, 1994). Unfortunately, data on effectiveness of cultivated and uncultivated plants in Se accumulation and as hosts for pest insects are minimal (Ban˜uelos et al, 1999).…”

Soil Metals and Ectomycorrhizal Fungi Associated with American Chestnut Hybrids as Reclamation Trees on Formerly Coal Mined Land

“…There was one exception; selenium, indicative of coal spoil, was higher than county and state averages and in the higher concentration range of common US soils. Also noted, drip lines were significantly lower in selenium than reference soils (soils lacking tree plantings or soil preparation [63] and it has been suggested that 4 ppm of selenium in plants is the tolerance limit for animals and levels above 5 ppm could be a concern [64]. Although we did not test levels in chestnut seed, we found floral tissue to average 7.3 ppm, which may merit closer inspection of the developing chestnut seed on legacy sites.…”

Developmental Responses of a Terrestrial Insect Detritivore, Megaselia scalaris (Loew) to Four Selenium Species

“…These results were not unexpected. Studies using insect herbivores (Hogan and Cole, 1988;Trumble et al, 1998;Ban˜uelos et al, 1999;Vickerman and Trumble, 1999), or insect predators (Vickerman and Trumble, 2003) also found reduced survivorship and/or delayed development. Our results show that Se contamination similarly affects insect detritivores.…”

“…In aquatic systems, insects feeding on algae are known to bioaccumulate Se (Malchow et al, 1995;Thomas et al, 1999) and are important primary consumers and prey in systems where bioaccumulation has been demonstrated (Lemly, 1993). In terrestrial systems, transfer of Se from plants to herbivores has been documented (Trumble et al, 1998;Ban˜uelos et al, 1999;Vickerman et al, 2002a, and references therein), as has the transfer from an herbivore to an insect predator (Vickerman and Trumble, 2003).…”