Fruit & Nut Research and Information Center
Fruit & Nut Research and Information Center
Fruit & Nut Research and Information Center
University of California
Fruit & Nut Research and Information Center

Sources & Sinks

Roots and foliage are complex structures that function as both sources and sinks. Image by Pro Web Design, Fotolia.com.
Roots and foliage are complex structures that function as both sources and sinks. Image by Pro Web Design, Fotolia.com.
The essential ingredients for plant life - water, nutrients, and light - are necessary for each part of a plant to survive and function. Without one ingredient, plants cannot acquire the other ingredients. For example, root cells need the energy provided by photosynthesis to take up water and nutrients, while leaves need water and nutrients (taken up by the roots) to perform photosynthesis and generate glucose.

These essential ingredients for plant life are taken up and produced in different parts of the plant. As a result, a substantial amount of tree biomass is dedicated to moving water, nutrients, and sugars between the places where they enter the plant and where they are used.

To describe where an essential resource is taken up or synthesized, and where it is used in a plant, biologists use the terms “source” and “sink”.

  • A source is a location in a plant where a resource is taken up (ex. water and nutrients) or synthesized (glucose).
  • A sink is a location where a resource is used.
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