pollination - process by which pollen is placed on the stigma
- can by carried by wind, animals, or flower itself
- early seed plants pollinated by wind
- large quantities of pollen shed, blown about
- must grow close together to work efficiently
- pollen travels less than 100 meters
- earliest angiosperms pollinated by insects
- bees - pollinates the majority of insect-pollinated angiosperms
- tend to visit blue/yellow flowers
- locates food first by odor, then by shape/color/texture
- use nectar as food for adult bees
- uses pollen as food for developing larvae
- mostly solitary
- insect pollinators other than bees
- butterflies - perch on the landing platforms of phlox flowers
- target heavily scented flowers (easier to find in the dark)
- birds - especially hummingbird/sunbird
- targets flowers w/ lots of nectar (not attractive to insects)
- attracted by the red color
- wind-pollinated angiosperms have small/greenish/odorless flowers
- reduced/missing corolla
self-pollination - mostly in flowers w/ small flowers in temperate regions
- don’t need pollinators to produce seed >> uses less energy, able to grow where animals are scarce
- creates more uniform populations
- outcrossing - necessary for adaptation/evolution
- dioecious plants - produce only ovules or pollen, cannot self-pollinate
- monoecious plants - produce both ovules/pollen, must produce gametes at different times to prevent self-pollination (dichogamous plants)
- self-incompatibility >> locus prevents self-pollination, pollen tube gets blocked
angiosperm double fertilization - creates fertilized egg, endosperm to nourish embryo
- pollen tube - grows after pollen adheres to stigma
- pierces the style
- reaches embryo sac >> nuclei around egg cell disintegrates >> tube tip enters egg
- tube tip bursts >> 2 sperm cells released (1 fertilizes egg to form zygote, other forms w/ polar nucleus to form triploid endosperm)
- endosperm completely transferred to cotyledons in dicots (disappears after maturing)
- seed enclosed in fruit
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