Dynamics of Ni‐based defence and organic defences in the Ni hyperaccumulator, Streptanthus polygaloides (Brassicaceae)

Abstract

Plants use chemical defences to reduce damage from herbivores and the effectiveness of these defences can be altered by biotic and abiotic factors, such as herbivory and soil resource availability. Streptanthus polygaloides, a nickel (Ni) hyperaccumulator, possesses both Ni-based defences and organic defences (glucosinolates), but the extent to which these defences interact and respond to environmental conditions is unknown. S. polygaloides plants were grown on high-Ni and low-Ni soil and concentrations of Ni and glucosinolates were compared with those of the congeneric non-hyperaccumulator, S. insignus spp. insignus, grown under the same conditions. Ni contents were highest (4000 µg g −" dry tissue) in S. polygaloides plants grown on high-Ni soil. Glucosinolate content was significantly higher in S. insignus than in S. polygaloides suggesting that plants defended by Ni produce a lower concentration of organic defences. In a separate experiment, high-Ni S. polygaloides plants were exposed to simulated herbivory or live folivores to determine the inducibility of Ni-based and organic defences. Contents of Ni were not affected by either herbivory treatment, whereas glucosinolate concentrations were 30% higher in damaged plants. We concluded that the Ni-based defence of S. polygaloides is not induced by herbivory.

Nickel and zinc hyperaccumulation by Alyssum murale and Thlaspi caerulescens (Brassicaceae) do not enhance survival and whole‐plant growth under drought stress

“…Several studies have demonstrated that Zn or Ni hyperaccumulation can deter herbivory (e.g. Martens & Boyd 1994;Pollard & Baker 1997;Pollard, Dandridge & Jhee 2000;Davis & Boyd 2000), limit infection by pathogenic fungi (Ghaderian, Lyon & Baker 2000), and enrich the soils under their canopy with higher concentrations of toxic metals (Boyd & Jaffré 2001). In contrast, however, Ni-hyperaccumulation increased the susceptibility of Streptanthus polygaloides (Gray) to a mosaic virus (Davis, Murphy & Boyd 2001).…”

Spatial Imaging, Speciation, and Quantification of Selenium in the Hyperaccumulator PlantsAstragalus bisulcatusandStanleya pinnata

“…This intriguing idea has been termed the elemental defense hypothesis of metal hyperaccumulation (Martens and Boyd, 1994). Metal hyperaccumulation was found to be a potent form of defense against both herbivores and pathogens (Boyd and Martens, 1992;Pollard and Baker, 1997;Davis and Boyd, 2000;Ghaderian et al, 2000). Similarly, Se has been shown to protect plants from both herbivory and pathogen infection (Hurd-Karrer and Poos, 1936;Vickerman and Trumble, 1999;Vickerman et al, 2002;Hanson et al, 2003Hanson et al, , 2004.…”

Elevated expression of metal transporter genes in three accessions of the metal hyperaccumulator Thlaspi caerulescens

“…There is considerable debate concerning the ultimate evolutionary explanation of the hyperaccumulation trait. The herbivore defence hypothesis, which states that metal hyperaccumulation is a way to reduce damage by herbivory and parasitism (Boyd & Martens 1992) is presently favoured by most authors and supported by circumstantial experimental evidence Boyd, Shaw & Martens 1994;Pollard & Baker 1997;Davis & Boyd, 2000;Ghaderian, Lyon & Baker 2000).…”