The pistil of a self-incompatible flowering plant can recognize pollen, which has landed on, or been brought to, its stigmatic surface as self-pollen or non-self pollen, based on whether the S
-haplotype of the pollen is present or not present in the pistil. For the pollinations depicted, S1
pollen are recognized as self pollen by the pistil of S1S2
genotype and the growth of their tubes is arrested in the upper segment of the style; S4
pollen is recognized as non-self pollen and its tube is allowed to grow down to the ovary to effect fertilization. This reproductive trait allows flowering plants to prevent inbreeding and promote out-crossing.
Figure 2: Leaf strips of Petunia inflata are transformed with Agrobacterium tumefaciens carrying a transgene construct, and the transformed tissues are cultured for regeneration of transgenic plants. The ability to introduce genes into transgenic P. inflata plants allows in vivo studies of the function and structure/function relationships of the genes involved in self-incompatibility.