Pistil Signaling in Self-Incompatible Poppy: Does It Allow More Efficient Resource Allocation in the Pistil?
Bruce McClure* Division of Biochemistry, Christopher S. Bond Life Sciences Center, University of Missouri, Columbia, 240a 1201 East Rollins Street, Columbia, MO 65211, USA. Abstract: In the process of pollination, haploid pollen germinates on the stigma surface and a pollen tube grows through the diploid tissues of the pistil toward the ovary. The pistil has two basic functions: to prevent unwanted pollen from gaining access to the ovary and to support the growth of desirable pollen. Pollen-pistil signaling allows these different types of pollen to be distinguished. Self-incompatibility (SI) systems, controlled by the S locus, are the best-understood pollen-pistil signaling systems. Other SI systems have been investigated at the molecular level, but the physiology of pollen tube rejection is best understood in the field poppy, Papaver rhoeas. This species has a gametophytic SI system: Pollen is rejected when its S haplotype is the same as either of the two S haplotypes expressed in the
