The identification of F actin in the pollen tube and protoplast of Amaryllis belladonna

The production of protoplasts from the pollen of Amaryllis belladonna has facilitated a more direct investigation of the physiological and mechano-chemical basis of streaming. Cytoplasm is removed from an actively streaming protoplast or intact pollen tube and layered on a coated grid in a solution containing a low free calcium ion concentration. Under these conditions 6 nm thin filaments are observed. The thin filaments are morphologically identical with F actin and bind rabbit muscle HMM, forming characteristic arrowhead complexes that are dissociated by subsequent treatment with MgATP.