Autogamy vs Geitonogamy vs Xenogamy
| Feature | Autogamy | Geitonogamy | Xenogamy |
|---|---|---|---|
| Definition | Pollen from anther to stigma of the SAME flower | Pollen between different flowers on the SAME plant | Pollen between flowers of DIFFERENT plants |
| Genetic nature | Self-pollination (same genotype) | Self-pollination (same genotype — TRAP!) | Cross-pollination (different genotype) |
| Ecological nature | Self-pollination | Cross-pollination (needs agent) | Cross-pollination |
| Requires external agent? | No (cleistogamous flowers) | Yes (wind, insect, etc.) | Yes |
| Genetic variation produced? | None | None (KEY NEET TRAP) | High |
| Example | Commelina (cleistogamous) | Corn/maize (monoecious) | Papaya (dioecious) |
| Evolutionary advantage? | Ensures seed set in isolation | None — energetically wasteful | Promotes adaptation and fitness |
Outbreeding Devices Comparison
| Device | Mechanism | Example |
|---|---|---|
| Self-incompatibility | Pistil genetically rejects own pollen (S-allele matching) | Many flowering plants |
| Dicliny | Unisexual flowers (mono- or dioecious plants) | Papaya (dioecious), Maize (monoecious) |
| Dichogamy (Protandry) | Anthers mature before stigma becomes receptive | Sunflower |
| Dichogamy (Protogyny) | Stigma receptive before anthers mature | Many grasses |
| Cleistogamy (inverse) | Flowers never open — ensures self-pollination | Commelina (inbreeding, NOT outbreeding) |