Parts of a Tree
By Barb Stephens
Each layer of a tree cookie (cross-section) can tell us something about the tree's life and the climate in which it grew. Write the correct parts of the trees in the appropriate blanks.
cambium growth ring heartwood outer bark phloem xylem
Item 1 is called the ____________. It is a layer or zone of cells, just one cell thick, inside the inner bark. This produces both the xylem and phloem cells. This is where diameter growth occurs, and where rings and inner bark are formed.
Item 2 is the ____________ or inner bark. This layer carries sugar made in the leaves or needles down to the branches, trunks and roots, where it is converted into the food the tree needs for growth.
Item 3 is the ____________ or sapwood. This layer carries the sap back up from the roots to the leaves. Sapwood gives a tree its strength.
Item 4 is a ________________. The lighter portion is called the "early wood" (because it grows in the spring), and the darker portion the "late wood" (which grows in the summer). Together, they represent one year of growth.
Item 5 is the ____________. This develops as a tree gets older. It is old sapwood that no longer carries sap, and gives the trunk support and stiffness. In many kinds of trees, heartwood is a darker color than sapwood, since its water-carrying tubes get clogged up. The tree cookie above has not developed this yet.
Layer 6 is the ________________. This layer protects a tree from insects and disease, excessive heat and cold, and other injuries.
Answers: cambium, phloem, xylem, growth ring, heartwood, outerbark
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