Plants have mechanisms to avoid inbreeding mechanisms to favor out-cross breading
- Pre – pollination mechanisms – based on the floral biology
- Post – pollination mechanisms – self incompatibility
- Post – fertilization mechanisms. – Embryo abortion, inbreeding depression.
Pre – pollination mechanisms
- Degree of the separation of male and female organs.
- Temporal separation of male and female function within flowers such as anthers mature first, stigma becomes receptive first both mechanisms are more chance to out cross breeding.
- The degree of flower opening
- wide opening – more chance to cross pollination
- moderately opening – more chance to self pollination
- anthers dehisce before opening – greater chance to self pollination
- Geological isolation
- Chemical signals – some plants are used chemical signals to attract pollinators.
Outbreeding traits vs inbreeding traits
| Traits | Outbreeding | inbreeding |
| Flower count | many flowers | few flowers |
| Flower size | large flowers | small flowers |
| Flower color | bright | mono color |
| Nectarines | present | absent |
| scent | present | absent |
| anther position | far from the sigma | close to stigma |
| pollen quantity | many | few |
| stigma | well defined | poorly defined |
Post – pollination mechanisms – Self Incompatibility
self incompatibility is the process of fail to produce mature seeds by self pollination.
There are many mechanisms to obtain the self incompatibility.
- Pollen fail to germinate on stigma
- pollen tubes fails to develop down on style, not develop towards the ovules.
Post – fertilization mechanisms.
- Embryo breakdown – some plants do self pollination these plants will not produce mature seed.
- Inbreeding depression – reduction of the vigor, fitness, and productivity due to self fertilization.
Factors determine the balance between crossing and selfing of flowers
- Pollinator availability
- Mating systems
- Flowers morphology