plant defenses
DESCRIPTION
Plant defenses. Mechanical protection on leaf surface Secondary Chemistry Polymers or silica crystals that reduce digestibility Chemical toxins that kill or repel at very low concentrations Low nutrient concentrations (a defense or consequence of physiological limitation?). - PowerPoint PPT PresentationTRANSCRIPT
Plant defensesPlant defenses► Mechanical protection on leaf surfaceMechanical protection on leaf surface► Secondary ChemistrySecondary Chemistry
Polymers or silica crystals that reduce Polymers or silica crystals that reduce digestibilitydigestibility Chemical toxins that kill or repel at very low Chemical toxins that kill or repel at very low concentrationsconcentrations
► Low nutrient concentrations (a defense Low nutrient concentrations (a defense or consequence of physiological limitation?)or consequence of physiological limitation?)
Mechanical ProtectionMechanical Protection
►Spines Spines ►TrichomesTrichomes► Glandular hairsGlandular hairs
e.g., cactus, cotton, field beanse.g., cactus, cotton, field beans
Chemical warfareChemical warfare
► “ “Herbivores are between the devil Herbivores are between the devil and the deep blue sea”and the deep blue sea”
Digestibility ReducersDigestibility Reducers
►Cell wall components: cellulose and Cell wall components: cellulose and hemicellulosehemicellulose
► TanninsTannins Free in cytoplasmFree in cytoplasm Block action of digestive enzymesBlock action of digestive enzymes Bind to proteins being digestedBind to proteins being digested Interfer with protein activity in gut wallInterfer with protein activity in gut wall
► reduced growth rate, weight loss, reduced growth rate, weight loss, malnutrition.malnutrition.
ToxinsToxins
ToxinsToxins• HCN• 1,000 plant species sequester•3.5 mg/kg body mass = death•Blocks action of cytochrome oxidase•Cooking removes HCN (e.g. almonds)
Constitutive vs. Induced Constitutive vs. Induced DefensesDefenses
► Cost Cost ► e.g., Lignin vs. Proteinase inhibitorse.g., Lignin vs. Proteinase inhibitors
block catalytic activity of proteiolytic block catalytic activity of proteiolytic enzymes in animal gut by binding to enzymes in animal gut by binding to active site of enzyme moleculeactive site of enzyme molecule
Eating PlantsEating Plants
► “ “the plant world is not colored green; the plant world is not colored green; it is colored morphine, caffeine, tannin, it is colored morphine, caffeine, tannin, phenol, terpene, latex, … and L-dopa”phenol, terpene, latex, … and L-dopa”
Feeding specialization and Feeding specialization and plant defensesplant defenses
► PolyphagousPolyphagous► OligophagousOligophagous► MonophagousMonophagous
Eating PlantsEating Plants
► Mechanical breakdownMechanical breakdown► Microbial farmsMicrobial farms
Eating animals that eat plantsEating animals that eat plants
Ecology of HerbivoryEcology of Herbivory
► Is herbivory always bad?Is herbivory always bad?► Life history traits associated with Life history traits associated with
levels of herbivorylevels of herbivory► Co-evolutionary arms raceCo-evolutionary arms race
N-addition Treatment
Unfertilized Bulk Exponential
Seed
Mass
(g
)
0
2
4
6
8
10
Unfertilized Bulk Exponential
Bio
mass
(g)
0
10
20
30
40
50
60 UndefoliatedDefoliated
a
c
c
b
a
c
Unfertilized Bulk Exponential
Flo
wer
and
Pod M
ass
(g
)
0
2
4
6
8
10
12
a a
b
ab b
b
c
d,e d
ea
(a)
(b)
(c)
Ecology of HerbivoryEcology of Herbivory
► Apparency hypothesisApparency hypothesis► Resource Availability hypothesisResource Availability hypothesis
(carbon:nutrient balance hypothesis)(carbon:nutrient balance hypothesis)
Ecology of HerbivoryEcology of Herbivory
Ecology of HerbivoryEcology of Herbivory
Ecology of HerbivoryEcology of Herbivory