Jasmonic acid treatment and mammalian herbivory differentially affect chemical defenses and growth of wild mustard ( Brassica kaber )

Abstract

Jasmonic acid (JA) is a wound-related hormone found in most plants that, when applied exogenously, can induce increases in levels of chemical defenses in patterns similar to those induced by mechanical damage or insect feeding. Relative to responses to insect and pathogen attack, chemical responses of herbaceous plants to mammalian herbivore attack have been little studied. In a field experiment, we compared the effects of JA treatment and naturally occurring mammalian herbivory on the expression of trypsin inhibitors, glucosinolates, peroxidase activity and growth of wild mustard (Brassica kaber). Exogenous JA significantly increased trypsin inhibitor activity and glucosinolate concentration, and moderately increased peroxidase activity in the eighth true leaves of fiveweek-old plants, relative to untreated controls. In contrast, levels of these chemical defenses in the eighth true leaves or in regrowth foliage of plants that had 80% of their leaf area removed by groundhogs (Marmota monax) did not differ from that in undamaged and untreated controls. Although exogenous JA significantly elevated levels of chemical defenses, it did not affect height of plants through the season and only slightly reduced time to first flower. Groundhog herbivory significantly reduced height and delayed or abolished flowering, but these effects were not substantial unless coupled with apical meristem removal. We hypothesize that the lack of effect of groundhog herbivory on chemical defenses may be due in part to the speed and pattern of leaf area removal by groundhogs, or physiological constraints caused by leaf area loss. Despite having no effect on chemical defense production, leaf area loss by groundhogs was more costly to growth and fitness than the effects of JA application in this study, but only substantially so if coupled with apical meristem removal. We suggest that in general, costs of defense production in plants are likely to be minimal when compared to the risk of losing large amounts of leaf area or primary meristematic tissue. Thus, if they are effective at deterring herbivory, the benefits of inducible defense production likely outweigh the costs in most cases.

Enhanced glucotropaeolin production in hairy root cultures of Tropaeolum majus L. by combining elicitation and precursor feeding

“…Treatment of T. majus hairy roots with the combinations of ASA with MeJA and ASA with YE was more effective in increasing glucotropaeolin content than treatment with these elicitors alone. This additive effect provides further confirmation that induction of glucosinolate biosynthesis by various stresses is a complex response or series of responses in which SA-mediated pathway might interact with jasmonate-mediate pathway and neither exogenous SA nor MeJA by themselves fully mimic the response of glucosinolate-producing plants to pathogen or herbivore attack (Doughty et al 1995;van Wees et al 2000;Cipollini and Sipe 2001).…”

A Proteomic Profiling Approach to Reveal a Novel Role of Brassica napus Drought 22 kD/Water-Soluble Chlorophyll-Binding Protein in Young Leaves during Nitrogen Remobilization Induced by Stressful Conditions

“…N starvation and MeJA treatment were used to induce leaf senescence (Rossato et al, 2002; Gombert et al, 2006) and TI activity (Cipollini and Sipe, 2001;Etienne et al, 2007).…”

Can browsing by deer in winter induce defence responses in bilberry (Vaccinium myrtillus)?

“…As an alternative to clipping or natural herbivory, many laboratory studies have used exogenously-applied jasmonic acid or methyl jasmonate (MeJA) to elicit plant defence responses. Such chemical induction of plant defence systems is comparable to the responses caused by natural herbivory or pathogenic attack (Baldwin 1996;Cipollini and Sipe 2001;Pieterse et al 2012), although it cannot separate between different types of herbivore. Chemical induction of plant defence systems under natural field conditions may help us to understand how important plant defence responses are in ecological systems.…”

“…Ungulate browsing not only removes woody biomass, but may also influence physical or chemical composition of the plants (Fornara and Du Toit 2008). One indirect effect of browsing may be the induction of plant chemical defence systems leading to increased production of toxic defence compounds or compounds that reduce plant nutritional value (Seldal et al 1994a;Cipollini and Sipe 2001;Sampedro et al 2011). Consequently, ungulate browsing may have cascading effects on other organisms that feed on the plants, such as other herbivores or pollinators.…”

“…Consequently, ungulate browsing may have cascading effects on other organisms that feed on the plants, such as other herbivores or pollinators. Few studies, however, have tested the effect of mammalian herbivory on induced plant defence systems (but see Cipollini and Sipe 2001).…”