Question

what is the pressure flow or mass flow hypothesis?

Class 11th Bio!​

Answer 1

Answer:

Mass flow hypothesis is the theory that translocation of sugars in the phloem is brought about by a continuous flow of water and dissolved sugars between sources and sinks. (A source is the site of production of sugars, usually leaves, and the sink is the site of their utilization, for example the root system.)

Explanation:

Answer 2

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The Accepted mechanism used for the translocation of sugar from the source to sink is called the Pressure Flow Hypothesis .

Glucose is prepared at the source (by photosynthesis) it is converted to succorse (a Disaccharide).

The Sugar is then moved in the form of sucrose into the companion cells and then into the living Phloem seive tube cells by active transport.

This process of loading at the source produces a Hypotonic condition in the Phloem. Water in the adjacent xylem moves into phloem by osmosis.

As osmotic pressure builds up in the phloem sap will move two areas of low pressure. At the sink osmotic pressure must be reduced.

It is necessary to move the out of the phloem shape and into the cell which will use the sugar converting into energy, starch, or Glucose.

As Sugar are removed, the osmotic pressure decreases and water moves out of the the phloem.