![]() In contrast to indirect defences, the efficiency of lima beans' direct chemical defences under natural conditions has not been studied until now. In addition to directly attracting carnivores, VOCs of lima bean play a role in defence-associated signalling between plants, and as external signal for priming of induced indirect defences within a single plant. Both types of indirect defences have been investigated extensively for the last decade under laboratory – and, more recently, natural field conditions –. These indirect (carnivore attracting) defences include the release of herbivore-induced volatile organic compounds (VOCs) and secretion of extrafloral nectar (EFN). Lima bean (Fabaceae: Phaseolus lunatus L.) represents a prominent experimental model plant for studies of inducible indirect plant defences against herbivores. Our results indicate the general importance of analysing ‘multiple defence syndromes’ rather than single defence mechanisms in future functional analyses of plant defences. We show that in addition to extensively investigated indirect defences, cyanogenesis has to be considered as an important direct defensive trait affecting lima beans' overall defence in nature. We used natural chrysomelid herbivores and clonal lima beans with known cyanogenic features produced from field-grown mother plants. Since existing correlations do not by necessity mean causal associations, the function of cyanogenesis as efficient plant defence was subsequently analysed in feeding trials. Quantitative variability of cyanogenesis in a natural population of wild lima bean in Mexico was significantly correlated with missing leaf area. the release of toxic hydrogen cyanide from preformed precursors. In this study, we focus on the cyanogenic potential (HCNp concentration of cyanogenic glycosides) as a crucial parameter determining lima beans' cyanogenesis, i.e. In contrast, studies on direct chemical defence mechanisms as crucial components of lima beans' defence syndrome under natural conditions are nonexistent. Lima bean ( Phaseolus lunatus L.) is a model plant for studies of inducible indirect anti-herbivore defences including the production of volatile organic compounds (VOCs) and extrafloral nectar (EFN). ![]() ![]() In natural systems plants face a plethora of antagonists and thus have evolved multiple defence strategies. ![]()
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