Printed in Great Britain © Company of Biologists Limited 10.80 POLLEN-STIGMA INTERACTION IN BRASSICA OLERACEA: THE ROLE OF STIGMATIC PROTEINS IN POLLEN GRAIN ADHESION

The adhesion of pollen grains to the stigmas of Brassica oleracea was assayed after treatment of the stigmas with protease and/or cycloheximide. Treatment with protease alone adversely affected pollen grain adhesion. However, the adhesive properties of the stigma recovered fully if the stigmas were not pollinated until 2 h after treatment. Immersion of the stigmas in cyclo-heximide after protease treatment prevented any recovery of the stigmas ' adhesive properties. Cycloheximide treatment alone prevented pollen grain adhesion when pollination occurred later than 1-2 h after treatment but did not affect pollen grain adhesion if pollination occurred immediately after treatment. These results indicated not only that the surface-held proteins of the stigma are involved in pollen grain adhesion, but also that their turnover rate is rapid. Iso-electric focusing of extracts derived from stigmas after protease and cycloheximide treatment showed a marked decrease in staining intensity of 3 protein bands, one of which, a glycoprotein, is known to be present only when the self-incompatibility system is fully functional. These observations suggest a specificity of adhesion between higher plant cells in the presence of the cell wall