BIO3082 Lecture Notes - Lecture 11: Food Security, Phenology, Herbivore
Lecture 11 – Food security 2: Nutritional value of plants
Costs of Herbivory to Plants
• Been eaten:
o Loss of biomass
o Loss of nutrients
o Photosynthesis foregone – loss of leaf area
• Protein content
• Energy content
• Secondary metabolites
• Cost
o Defended leaves have lower C assimilation rate
o Defended leaves have smaller leaf areas
o C products = CO2 fixed/area/time x area x time
Liebig’s Law of Minimum (1873)
• Growth is controlled not by the total amount of resources available, but by the
scarcest resource (limiting factor)
• Fast growing plants – short lived
• Slow growing plants – long lived
Defence Strategies
• Physical (structural)
o Thorns
o Lignin
o Toughness
o Scleorphylly
▪ Thick cuticles – reduces digestibility
o Costs of physical defences
▪ Synthesis
▪ Maintenance
▪ Self shading
▪ Physical space – taking up space where it can be a leaf
• Behavioural (phenology: timing of events)
o Delayed greening
▪ Cost: no photosynthesis → very low protein content → not
eaten by animal
o How phenology impact on whether or not a plant is eaten
▪ Leaves produced only at certain times
• Seasonal responses (when no insects around)
• Synchronous production
▪ Delayed greening
• Maybe loaded with chemicals
• Low in protein (not worth eating)
• Defer investing in leaves until they are productive and
safe
• Chemical (secondary metabolites)
o How do chemicals that plants make reduce herbivory?
▪ Defer herbivores – toxic, bitter
▪ Reduce vigour of herbivores
find more resources at oneclass.com
find more resources at oneclass.com
