BIO3082 Lecture Notes - Lecture 12: Phenotypic Plasticity, Global Change, Resource Allocation
Lecture 12 – Predicting the Future
Cyanogenic Glucosides
• Enzyme that breaks sugar off → releases cyanide
• Cyanogenesis = prussic acid = HCN
Resource Trade-Off
• Defence would make you live longer
o Affects total C gain → affects reproduction yield/food
• Effect of global changes e.g. rising CO2
o Depends on level of defence is result of
▪ Adaptation through evolution – genetic basis
▪ Acclimation to physical environment – phenotypic plasticity
▪ Level of herbivore pressure (space, time)
Plant Defence Theories
• Relates to costs/benefits
• Assume
o Limited availability of resources
o Herbivore (pathogen pressure)
• Confusion over context
o Evolutionary vs. phenotypic plasticity
o Acquisition vs. allocation of resources
• Costs rarely tested
o Usually just used to explain results
• Optimal Alocation Defence Theory
o Resource allocation
o Plants or parts of plants that are more valuable or vulnerable will be
more highly defended
o Valuable
▪ Contribute to C balance
▪ Contribute to reproduction
o Vulnerable
▪ More palatable, tasty (new leaves)
More obvious
▪ Longer lived
• Apparency Theory
o Plants that are long-lived have a greater chance of being discovered by
herbivores
o Long lived plants will be more highly defended with metabolically
cheap products (quantitatie)
▪ E.g. seedlings in rainforest
o Short lived plants will use small concentrations of highly toxic
compounds (qualitative)
• Carbon/nutrient balance hypothesis
o Resources are only diverted to secondary
metabolites when they are in excess of that
required by growth
o Overflow hypothesis
o Theory is simple but inadequate
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