Explain pressure flow hypothesis of translocation of sugars in plants.

Explanation

Glucose is prepared at the source is converted to sucrose, then moved into the companion cells and then into the living phloem sieve tube cells by active transport. Water in the adjacent xylem moves into the phloem by osmosis. As osmotic pressure builds up, the phloem sap moves to the cells which will use the sugar converting it into energy, starch or cellulose. As sugars are removed, the osmotic pressure decreases and water moves out of the phloem.
To explain this, Munch conducted one experiment. In this, he took two osmometers A and B. In .B. he took concentrated sugar solution and in A, he took pure water. These two bulbs A and B are connected by a tube, .C. He then, placed A and B bulbs in X and Y water tubs which are connected by tube .Z.. Due to osmosis, water moves from A to B, B to A through C and then A-X and finally X-Y through Z occurs until the solution becomes isotonic. In this he compared .B. bulb as source, A. bulb as sink, C tube as phloem, X and Y tubs are xylem