Explain briefly Mass flow Hypothesis.

Explanation

The accepted mechanism used for the translocation of sugars from source to sink is called the pressure flow hypothesis. The glucose prepared by photosynthesis is converted to sucrose and is then moved in the form of sucrose into companion cells and into sieve tube cells by active transport. This loading creates hypertonic condition in the phloem & water in the adjacent xylem moves into the phloem by osmosis. As osmotic pressure builds up the phloem sap will move to areas of lower pressure. Again by active transport sucrose is transported out of phloemsap into the cells where it is used to convert into enery, starch or cellulose.