Pollinisation incompatible d’une Arabette des dames
Incompatible attempted pollination of thale cress (arabidopsis thaliana), observed using scanning electron micrsoscopy. Here, the surface of the female reproducitve organ, the stigma, formed of elongated cells, the stigmatic papillae, rejects all pollen grains. The plant will not be fertilised. Despite encountering hundreds of grains of pollen, the female reproductive organs of plants are able to choose their male partners very quickly. In the case of brassicas (the group that includes cabbages, radishes, rockcress, etc.), this choice depends on a lock-and-key type interaction, the key (a peptide) being introduced by the pollen whereas the lock (a membrane-associated kinase receptor) is present on the plasma membrane of the stigma cells. If the key and the lock are genetically related (being brother and sister, for example), the lock-and-key interaction prompts the stigma to reject the pollen. This mechanism enables the plant to avoid inbreeding.