Transport in Plants

Phloem Transport

  • As the leaves produce starch as a result of photosynthesis, it is converted to sucrose to get transported to various parts of the plant.
  • Sucrose production is noted as source (or) phloem loading and the target point is referred to as sink (or) phloem unloading.
  • The sucrose enters the sieve tube by piercing companion cells [Active transport with symplastic pathway) and mixes with water that enters from the adjacent Xylem into sieve tube due to osmosis to form sap.
  • The sap at one end creates high hydrostatic pressure and hence moves along the sieve tube until the bottom point where hydrostatic pressure is low through passive transport.
  • Again the sap through symplastic pathway crosses the companion cells to reach the sink.
  • During unfavourable seasons, food molecules are moved from the roots (source) to leaf (sink).
  • Phloem transport of food is also considered to be a mass/ bulk/pressure flow by a scientist named Munch with help of a flowmeter.

View this video for the topic from 48:02 to 53:38

Disclaimer: may from time to time provide links to third party Internet sites under their respective fair use policy and it may from time to time provide materials from such third parties on this website. These third party sites and any third party materials are provided for viewers convenience and for non-commercial educational purpose only. Compete does not operate or control in any respect any information, products or services available on these third party sites. makes no representations whatsoever concerning the content of these sites and the fact that has provided a link to such sites is NOT an endorsement, authorization, sponsorship, or affiliation by with respect to such sites, its services, the products displayed, its owners, or its providers.