Differences of S-glycoprotein Content in the Styles among Pear Cultivars Differing in Self incompatible Strength A Study on the Regulating Self􀀁incompatibility of Brassica oleracea L. by Inhibitor or Activitor of Protein Kinase A Study on the Regulating Self􀀁incompatibility of Brassica oleracea L. by Inhibitor or Activitor of Protein Kinase Differences of S-glycoprotein Content in the Styles among Pear Cultivars Differing in Self incompatible Strength