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Types of pollination

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     When pollen is transferred from an anther to a stigma, it may be transferred within one flower (shown in the diagram on the right) or between two flowers (as shown in the diagram on the left). If the flowers are on two different individual plants, the flower has been cross pollinated whereas if the flowers are on the same individual, or if the anther and stigma are in the same flower, the flower has been self pollinated. Flowers that are self pollinated and can produce viable seeds are self compatible. Flowers that are self pollinated but the pollen does not function properly on the carpels of the same  plant are termed self incompatible.     
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Cross pollination

Self pollination

Cross pollination is believed to be advantageous for the plant because the seeds produced by the flower will contain another source of genetic material which may contain genes which are advantageous to the survival of the seedlings. Plants that self pollinate are said to be inbreeding whereas plants which only cross pollinate are said to be outcrossing. However, most plant species are not strictly inbreeding or outcrsossing but a combination of the two. 

 

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