Presentation bio about phloem and translocation.pptx

About phloem and translocation

1. Phloem and Translocation S.Subabharathiselvan B.sc (Blended) Physics Reg No :24BPH006

2. What is Phloem Phloem is one of the two main vascular tissues in plants, the other being xylem. While xylem carries water and minerals from roots to leaves, phloem transports food produced during photosynthesis to different parts of the plant. Unlike xylem, phloem conducts materials in both upward and downward directions.

3. Structure of Phloem Phloem is made up of four main components: 1. Sieve Tube Elements –These are long, tube-like cells that conduct food. They have pores at their ends called sieve plates. 2. Companion Cells – These cells are closely associated with sieve tubes and help in loading and unloading of food materials. 3. Phloem Parenchyma –These cells store food and assist in transport. 4. Phloem Fibres –These are dead cells that give mechanical strength to the phloem.

4. What is Translocation? The movement of food materials (mainly sucrose) through the phloem is called translocation. It occurs from the source (where food is produced, usually leaves) to the sink (where food is used or stored, such as roots, fruits, or seeds).

5. Source and Sink Source : Where food is produced (e.g., leaves during photosynthesis ) Sink : Where food is needed or stored (e.g., roots, fruits, growing buds) Movement in phloem can be upward (or) downward Bidirectional

6. Mass Flow Hypothesis

7. Mechanism of Translocation The most accepted theory explaining phloem transport is the Pressure Flow Hypothesis, proposed by Ernst Münch . 1. Loading at the Source : Sugars are actively transported into the phloem from the leaf cells. This causes water to enter by osmosis, increasing pressure in sieve tubes. 2. Movement through Phloem : The high pressure pushes the sugary sap through the sieve tubes toward the sink. 3. Unloading at the Sink : Sugars are removed from phloem at the sink region for use or storage. Water then moves out, reducing pressure . This process continues as a mass flow from high pressure (source) to low pressure (sink).