How is Food Transported in Plants?

Just as humans have blood vessels, plants have a specialized vascular tissue called the Phloem. The primary job of the phloem is to transport the soluble products of photosynthesis (food) from the leaves to all other parts of the plant.

The process of transporting food through the phloem is called Translocation. Unlike water transport (which only goes UP from roots to leaves), translocation is bi-directional; it goes both UP and DOWN to wherever food is needed (roots, growing shoots, or developing fruits).

1. Loading: The food (sucrose) prepared in the leaves is actively loaded into the phloem sieve tubes. This process requires energy in the form of ATP.
2. Osmosis: As the sugar concentration in the phloem increases, water from the neighboring xylem tissue enters the phloem by osmosis.
3. Pressure Gradient: This influx of water creates a high osmotic pressure inside the phloem, pushing the food-rich sap towards areas of the plant that have low pressure (where food is needed).
4. Unloading: The food is absorbed by the cells that need it, and the water returns to the xylem.