title: Freeze-fracture analysis of phloem structure in plant tissue cultures. III. P-Protein, sieve area pores, and wounding.
abstract: Phloem sieve elements in small nodules of callus tissue have open sieve pores and scattered P-protein when the tissue is fixed intact. Intentionally slicing the nodules prior to fixation results in the formation of wound responses, including an alteration in P-protein distribution and the formation of plugged sieve pores. Freeze-fracture replicas show well-preserved P-protein as randomly oriented filaments in intact sieve elements. Wounded sieve elements, however, demonstrate dense bundles of oriented P-protein filaments in freeze-fracture replicas. Open pores with few P-protein filaments are seen in replicas of undamaged sieve elements. These callus nodules can be used as a model system to investigate phloem structure, function, and wounding.
mesh_terms: D002462:Cell Membrane / Q000648:ultrastructure; D046508:Culture Techniques; D005614:Freeze Fracturing; D008854:Microscopy, Electron; D010940:Plant Proteins / Q000032:analysis*; D010944:Plants / Q000032:analysis / Q000648:ultrastructure*
chemical_list: D010940:Plant Proteins