Plant-Animal Interactions Flashcards
Types of interactions
- Herbivory
- Protection against herbivores
- Pollination
- Seed dispersal
- Plant carnivory
What is the estimated value of pollination?
$168.75 billion in 2009
What is pollination?
Pollen movement from anther to stigma
What is the other name for wind pollination
Anemophily
What is insect pollination called?
Entomophily
Features of wind pollination
Abiotic
Gymnosperms and some flowering plants (grasses, trees) use wind pollination
Flowers are small and grouped together
Not very efficient method (chancy and wasteful)
Biotic pollination
Animal pollination Usually a mutualism Insects - bees, wasps, butterflies Birds - hummingbirds, honey creepers Mammals - monkeys, bats, mice Other - slugs, reptiles, frogs
What is floral advertising?
Advert requires that there is a signal that animals can detect
And there must be a reward for learning to detect the signal
Different animals have different senses so signalling must vary
Different pigments produced by plants for flower colour
Carotenoids
Flavonoids: flavonols and anthocyanins
Bilirubin
Betalains
Carotenoids
Found in daffodils Important in photosynthesis Can help dissipate excess light (photoprotective) Amount of carotenoid determines colour Found in flowers and fruits
Flavonoids
Flavonols and anthocyanins
Usually synthesised and stored in vacuoles
Host of different functions
Importance in defence against pathogens
Part of signalling pathway in rhizobia
Protect against high levels of UV by producing antioxidants (anthocyanin)
Also can form complexes with metal ions and help plants survive in metal-contaminated soil
Colour of anthocyanins
Vivid red and oranges
Colour of flavonols
Mainly reflect UV, so cannot be seen by humans but important for insect/bird pollinators
Can act as a colourless co-factor (contributes to flower colour by stabilising anthocyanins or other pigments in the flower
Bilirubin
Bluish colour of bruises (metal-based pigment)
Betalains
Colour of deep red beetroot
Found in some cacti species
Shape of cells on petals
Difference between conical cells or flat cells on surface of petal changes colour of petal
What colours can a bee see
UV, blue and green photoreceptors (trichromatic)
Flower that uses echolocation
Marcgravia evenia
Disc-shaped leaf
Ring of flowers, shedding pollen
Cup-like nectaries
What else is a tactical cue to bees besides colour?
Flower petal microtexture
Co-evolution in animal-plant interaction
- Plants evolve elaborate methods to attract animal pollinators
- Animals evolved specialised body parts and behaviours that aid interaction with flowers
False floral advertising example
Orchid Chiloglottis trapeziformis deceives male Neozeleboria cryptoides wasps into thinking they are mating with a females
Chiloglottone js the active component that is produced by the orchid and female wasps
Pollinator syndromes
Pollination by beetles: cantharophily Pollination by bats: chiropterogamy Pollination by water: hydrophily Pollination by bees: melittophily Pollination by ants: myrmecophily Pollination by birds: ornithogamy Pollination by butterflies: pyschophily
Pollination by bees
Melittophily
They live on the nectar and feed larvae the pollen
Guided by sight, smell and touch
Flowers predominantly pollinated by bees usually have landing platforms
Radially symmetric / zygomorphic
Flowers are yellow or blue with UV nectar guides
Pollination by birds
Ornithogamy They live on the nectar Large orange or red tubular flowers Dilute nectar secreted during the day Usually odourless
What are special ways in which bees collect rewards from plants?
Buzz-pollination
Oil-harvesting
What other rewards besides nectar do plants offer insects?
Pollen, oil or wax
Nursery / brood-site
Heat - metabolic reward
Cheating by pollinators
Pollinators can cheat the flower and rob nectar without carrying out pollination
Plant mimicry
False advertising: flowers of unrewarding orchid Disa nervosa mimic rewarding flowers of iris Watsonia densiflora
Some flowers mimic insect shape and colouring e.g. Ophrys speculum pollinated by Campsoscolia ciliata
What are perfect flowers?
Have both male and female parts in them
Inbreeding depression example
Unfavourable effects come from inbreeding
E.g. Banksia spinulosa selfing led to a 63% reduction in seed set
What can self-pollination lead to?
Reduction in seed size, fruit set, fruit quality
Methods to prevent inbreeding and ensure outcrossing
- Timing of flowering
- Morphological differences
- Biochemical
- Developmental
Pollen-pistil interaction prior to fertilisation
- Pollen capture
- Pollen adhesion
- Pollen hydration
- Pollen germination
- Pollen tube penetration of the stigma
- Growth of pollen tube towards the ovule
- Entry of pollen tube into the ovule leading to fertilisation
The S locus
SI is controller by a single locus, S, with multiple alleles, S(1), S(2), S(3), etc.
The S locus is highly polymorphic: populations maintain around 40 S alleles by negative frequency-dependent selection
Summary of double fertilisation events
- Pollen tube penetrates synergid and released sperm nuclei; the tube nucleus degenerates
- One sperm fuses with the egg to form a diploid zygote
- Second sperm fuses with the two polar nuclei to form a triploid endosperm, which nourishes the developing embryo sporophyte
The endosperm
Following fertilisation the triploid endosperm nucleus divides repeatedly to form a mass of protoplasm and nuclei without cell division and acquiring nutrients from the sporophyte. As the seed matures the endosperm undergoes cellularisation.
Food resources are thus only laid down in an ovule/seed after fertilisation
What is a fruit?
A structure formed from parts of the flower or influorescence that contains the seeds
Ovary = fruit
Ovule = seed
What percentage of human food comes from seeds
70%
Pre-dispersal hazards
- Incomplete pollination
- Self pollination (eg. by geitonogamy) leading to ovule abortion or incomplete fruit set
- Resource limitation or stress leading to ovule abortion or incomplete fruit set
- Pre-dispersal seed predation
What is a fuses carpel-like structure containing many ovules called?
A pistil