Self-fertilization in plant: How common is it? How does a plant prevent it from happening?

Question

A statistic of how often self fertilization occurs in plants would most likely get best answer from me.

Answer 1

I really highly doubt there's a single statistic for how often plants as a whole self-fertilize. If there was, I'd be impressed at any botanist who could analyze hundereds of thousands of plant species and average everything together.

That being said, some plants self fertilize way more than others.

Orchids and lilies almost never self-fertilize. Lots of mechanisms can accomplish this, for example....

-Self-genetic recognition ability; i.e. proteins recognize sperm from the same plant and destroy it, or sperm is incapable of forming pollen tube on stigma of identical genes

-Physical seperation of male and female plant parts

-Imperfect flowers (male and female flowers seperate)

-Completely single gender trees (monoecious vs. dioecious, this occurs in familiar species like willow)

-Pollination by specific pollinating factors, like bees

Plants can be obligate selfers, obligate outcrossers, or some combination of both. Sometimes it even varies within particular plant species - sometimes the plant likes to self, sometimes it likes to outcross.

As a general rule, wind-pollinated plants (grasses, Betula, etc.) self fertilize more often than pollinator-pollinated plants (Orchids, lilies, showy flower type plants).

Hope that helps.