EFFECT OF CYTOCHALASIN B ON DIVISION AND ULTRASTRUCTURES OF ROOT MERISTEMATIC CELLS OF ONION BULES Effects of Cytochalasin B and Phalloidin on Pyrus pyrifolia Self-incompatible Pollen Germination and Tube Growth Effects of Cytochalasin B and Phalloidin on [Ca2+]i Concentration and Ca2+ Channels in the Plasma Membrane of Pyrus pyrifolia Pollen Tube Cutting edge Cellular Networks in Epidermal Peels of Onion