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.