Translocation in phloem is achieved by utilizing energy, with substances like sucrose transferred using energy from ATP. This increases osmotic pressure, causing directional movement of materials in the phloem to tissues with lower pressure, allowing for material transport as per the plant’s requirements.
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Translocation in the phloem is achieved through a process called pressure flow mechanism. It begins with the active loading of sugars, primarily sucrose, into the sieve tube elements in source regions (like leaves) by companion cells. This creates a high concentration of solutes, leading to water influx into the sieve tubes. The resulting positive pressure forces the sap, containing sugars and other substances, to flow toward areas of lower pressure, such as sinks (growing tissues or storage organs). ATP, generated during cellular respiration in companion cells, fuels the active transport of sugars into the sieve tubes, providing the energy necessary for loading and maintaining the pressure flow mechanism.