Pollination is the transfer of pollen grains from the anther to stigma.
Self pollination - transfer of pollen grains from the anther of a flower to a stigma of the same flower or different flower on the same plant.
Cross pollination - the transfer of pollen grain from the anther of a flower on one plant to the stigma of a flower on another plant of the same species.
NB have to be the same species to reproduce.
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Promotion of cross pollination
- Non-synchronous maturation of stamens (protogyny) and carpels (protandry)
- Protogyny - when stigma matures and is ready to accept pollen but anther is not mature yet to release pollen
- Protoandry - when anther is mature and release pollen grains but stigma is not mature yet to accept pollen
- Dioecy - plant has separate sexes where trees produce either male of female flowers. NB male trees are nearby for the female trees to produce fruits so self pollination if impossible
- Self incompatibility - if a pollen grain has an allele that is the same as one on a stigma it will not germinate. so gene determines whether pollen grains germinate and grow on stigmatic surfaces
- Male sterility - some mutations result in failure to produce pollen grains which resulted from genes on chromosomes in nucleus and also genes in mitochondria
- Heterostyly - the existence of plants with two types of flowers with a species. some plants have anther above stigma (style short) and some plants have anther below stigma (style long). NB therefore insect pollinators transfer pollen from flowers with short styles to flowers with long style and from flowers with long style to flowers with short style
diagram of heterostyly
