Nickel defends the South African hyperaccumulator Senecio coronatus (Asteraceae) against Helix aspersa (Mollusca: Pulmonidae)

Abstract

The elevated Ni concentration of Ni hyperaccumulator plants has been proposed to be an effective chemical defence against herbivores. To test this hypothesis, we fed leaves from hyperaccumulator and non-hyperaccumulator populations of South African Senecio coronatus to a generalist herbivore species, the brown garden snail (Helix aspersa). Snails fed hyperaccumulator leaves experienced significantly greater mortality than those fed non-hyperaccumulator leaves and also contained 10-fold greater concentrations of Ni. A choice experiment showed snails preferred non-hyperaccumulator leaves in two of three trials. Snails fed cornmeal diet amended with Ni had significantly reduced mass for diets containing as little as 140 mg Ni g − 1 , and significantly greater mortality occurred for snails consuming diets containing 830 mg Ni g − 1 and greater. Because hyperaccumulator S. coronatus leaves contained far more Ni (12,100 mg Ni g − 1 ) than the toxic threshold shown in the diet experiment, we concluded that the Ni concentration of hyperaccumulator leaves was sufficient to cause the elevated mortality of snails fed those leaves. This research adds another example to the growing literature showing the toxicity of hyperaccumulated Ni to generalist folivores.

A test of elemental defence against slugs by Ni in hyperaccumulator and non-hyperaccumulator Streptanthus species

“…For Ni, plant defence against herbivores has been explored by a number of studies (Boyd 1998;. In general, hyperaccumulator concentrations of Ni are effective against folivores Boyd & Moar 1999;Boyd et al 2002;Jhee 2004), rhizovores (Jhee 2004) and some cell-disrupting herbivores (Jhee 2004), but not vascular tissue-feeding insects or other cell-disruptors (Boyd & Martens 1999;Jhee 2004).…”

Complexation and Toxicity of Copper in Higher Plants. I. Characterization of Copper Accumulation, Speciation, and Toxicity inCrassula helmsiias a New Copper Accumulator

“…These plants, which accumulate up to several percent of heavy metals in the dry mass of their aboveground parts, are called "hyperaccumulators" (Brooks et al, 1977). In their natural habitats, metal-rich soils in many parts of the world, this type of heavy metal accumulation serves as a defense against pathogens and herbivores Martens and Boyd, 1994;Boyd et al, 2002;Hanson et al, 2003;Jhee et al, 2005). They can now be used for the decontamination ("phytoremediation") of anthropogenically heavy metal-contaminated soils and in some cases also for the commercial extraction ("phytomining") of high-value metals (mainly Ni) from metal-rich soils (Baker et al, 1994;McGrath and Zhao, 2003;Chaney et al, 2005).…”

Oxalic Acid/Oxalates in Plants:From Self-Defence to Phytoremediation

“…by hyperaccumulators [38][39][40][41] , which are being utilized in phytoremediation of soils affected by toxicity of these heavy metals. This toxicity in soils may be caused by the continuous use of sewage sludge 42 or closeness to zinc or lead smelters [43][44][45] or due to other natural causes.…”