But if they mature at different times, self-fertilization is avoided. Heteromorphic flowers . A single plant has one type or the other. If the pollinator has a short tongue, pollination is favored from the first type to the second - but not the reverse. Homomorphic flowers .
All flowers have exactly the same structure.
There are two quite different types of self-incompatibility. In this system, Rejection of self pollen is controlled by the diploid genotype of the sporophyte generation . Kinases attach phosphate groups to other proteins. SRK is transmembrane protein embedded in the plasma membrane of the stigma cell. In the example shown here, the S 2 pollen, which was produced by a S 1 S 2 parent, cannot germinate on an S 1 S 3 stigma.