Bundles of microfilaments very similar in
appearance to actin are present in cytoplasmic suspensions
obtained from Nitella flexilis. The microfilaments bind
rabbit heavy meromyosin in arrowhead arrays similar to
those produced on muscle actin. The arrowheads are
removed with ATP. The results provide evidence that actin
is present in green plants, probably in the form of microfilaments
thought to be involved in cytoplasmic streaming.