This suberized region of endodermal cells prevents apoplastic entry of water into the stele. Of the three routes of lateral water transport in roots, one is the transmembrane route which passes through the most cells walls and membranes. The second is the symplastic route which only passes through one plasma membrane. Name the third lateral transport route. Explain why the proton pump enhances the facilitated diffusion of cations into a plant cell.
Bulk flow is involved in long distance transport of xylem sap.
In a tree the xylem stream must be continuous for water to be pulled up. Explain why an ongoing supply of ATP is required for translocation to continue for very long. Bulk flow is involved in translocation. When an aphid feeds, it inserts its stylet into a single sieve tube member and is force fed with a sugar solution. As Dr. Coffman described, ants herd and care for aphids much as we do with cows because ants like the honey dew which oozes out from these pressure fed insects.