angiorepro213-page12 - achieve the goal of pollen transfer...

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Flowering Plant Reproduction - 12 Pollination and Pollinating Agents Pollination is the transfer of pollen (containing sperm) from one flower to a second. Since plants cannot move, and sperm in flowering plants is not motile (no flagella), sperm transfer requires a pollinating agent. This dependency poses some problems for the typical plant: You must attract an agent You must have adequate pollen for transfer You must convince the agent to take your pollen to another flower of your species (usually by providing a reward) In fact, you want to be so special that the pollinating agent will visit your species exclusively, for at least the time that you are in flower. (Because pollen production takes energy, which should be conserved whenever possible.) You do not want to produce too much of an attractant or reward because your pollinator must leave you and go visit another flower of your species in order to
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Unformatted text preview: achieve the goal of pollen transfer. Filling up on you or taking your pollen to a different kind of flower is not useful Types of Pollination • Cross-pollination ± Different flower • Self-pollination ± Same flower Most plants have mechanisms that ensure cross-pollination, which produces more genetic variation. Some plants have back-up self-pollination if no pollinator visits within the needed time frame, and some plants exclusively self-pollinate. Some of the common mechanisms that promote cross-pollination are • Dioecious plants, and to some lesser extent monoecious plants • Pollen and eggs may mature at different times, a phenomenon called dichogamy. Protandrous plants have mature stamens first, and protogynous plants have mature carpels first. Dichogamy in Fireweed, Epilobium angustifolium...
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