Protoplasmic Streaming and Tubular Peristaltic Flow Model

The first of the above two models involves the well known phenomenon of cytoplasmic streaming in giant algal cells. Coupling the regular cyclic movement of cytoplasm with active transport across sieve plate pores is thought to lead to a net flux of phloem sap in the direction of sinks.

But even the highest estimates of movement by cyclosis are inadequate to explain the observed rates of transport through phloem. The second model is based on the hypothesis of trans-sieve element tubular structures which undergo peristaltic movements similar to the action of our alimentary canal. Both models need experimental support.