Oregon State University

Sex Determination

Sexual determination in plants

1. The degree of outcrossing ranges from complete (dioecy)……to……moderate (monoecy) ……to……(very) low (hermaphrodites)


2. Perfect flowers: 90% of angiosperms are hermaphrodites - they have perfect flowers. The ancestral and basal condition is hermaphroditic

A. The benefits of outcrossing often outweigh the drawbacks.


    • Avoids inbreeding depression
    • Promotes heterozygosity
    • Promotes genetic variability


    • Environmental conditions may limit pollen flow
    • "Cost" of having two parents, only one of which bears seed

B. Even in the case of perfect flowers, there are ways of encouraging, or even requiring, outcrossing.

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