Why do trees produce sap?

(Image credit: Nick Windsor/ Pixabay)

Question from Dora Esra

Tree sap is a fluid consisting of water, hormones and minerals, which is transported via the xylem or phloem cells of a tree, depending on what kind of sap it is. Phloem sap contains sugars and  travels through the phloem cells from sugar-rich areas of the tree, like the leaves, to distribute the sugars, hormones and minerals to sugar-poor areas, such as the trunk and roots. 

The other type of tree sap is known as xylem sap, which travels through xylem cells. Also consisting of dissolved hormones and minerals- but not sugars- this type of tree sap includes nutrients from the environment too, and travels up from the tree’s roots to the leaves. By transporting such goodness, sap is a vital part of a tree’s life, essential for its health and development.

Different species of trees have different sep profiles. For example, sap from the manchineel tree contains so many toxins that it can cause burns, blistering and inflammation by just touching it. On the other hand, sap from the maple tree is so safe it’s even edible. 


Answered for Brain Dump in How It Works issue 96.

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