Name: Transport Mechanism in Plants
Uploaded: 2019-07-19
Duration: 5 min
Description: Plants contain a vast network of conduits which consist of the xylem and phloem. This is more like the circulatory system. Learn more.

Question

Explain capillarity theory of water translocation.

Accepted Answer

Bohem in 1863 proposed the capillarity theory of translocation of water through xylem. According to this theory, physical forces and dead cells are responsible for ascent of sap. Capillarity is because of surface tension. Additionally, the forces of cohesion and adhesion also play role in upward movement of the water through the narrow vessels of xylem. Xylem vessel/ tracheid with its lumen is comparable with straw. Water column exist because of combined cohesive and adhesive forces of water and xylem wall, due to capillarity. It is because of capillarity water is raised or conducted upwards against the gravity, to few centimetres only.

However, the major drawbacks are:

The lower end of xylem is not in direct contact with water (or dipped in water) as needed for capillarity to continue.

The width of the vessels (capillary) plays vital role in distance of water travelled through it. Tall trees have quite wide vessels to lift water to a great height.

Explain capillarity theory of water translocation.

Important Questions on Plant Water Relation

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