Translocation

• Translocation


  The transport of nutrients in the phloem from sources to sinks
• Sources


  • Parts of the plant that release sucrose or amino acids
  • Regions of production like the Palisade mesophyll tissue in the leaves
  • Storage like tubers which release sucrose at certain times of the year
• Sinks


  • Parts of the plant that receive sucrose and amino acids
  • Areas of active growth like developing seeds, leaves and flowers
  • Areas of storage like roots, stems, tubers and bulbs
• Sucrose is transported from its source in the leaves


  To sinks like the roots and stem where it's converted to the insoluble molecule starch and stored
• Sources and sinks are not always fixed, the movement of dissolved sucrose and amino acids is bi-directional
• Leaves begin life as net nutrient sinks


  As newly forming buds rely on carbohydrates and other nutrients for respiration and growth
• As the leaf develops and the rate of photosynthesis rises


  Leaves ultimately become net nutrient sources supplying sucrose and amino acids to the rest of the plant
• Tubers start off as sinks


  As soon as new leaves start to grow on the plant they become sources
• Insoluble starch is converted to soluble sucrose


  Which enters the phloem and moves up the stem to the buds