Incompatibility - Pollination and Fertilization
Plants growing under natural conditions have a preference for their mating partners. The stigma of the female parent receives all kinds of pollen. However, the choice of pollen of the desired parent that would accomplish fertilization is finally determined by both, pistil and the pollen. This gametophyte (pollen) and sporophyte (pistil) interaction leads to recognition (acceptance or rejection) of mating partners. In angiosperms, the female gamete is located in the ovule present in the ovary.
Therefore, pollen grains carry male gametes through pollen tubes that travel from stigma to ovary to affect fertilization. The pollen tube has to traverse through the tissues of the stigma and style. A situation in which fertile pollen fails to accomplish fertilization process so that a viable embryo seed is not formed is sexual incompatibility. Self-incompatibility means the inability of the plant producing functional gametes to set seed upon self-pollination. It may operate between the individuals of the same species-intra specific or self-incompatibility or of different species-inter specific incompatibility.