Translations:Adventist Youth Honors Answer Book/Nature/Trees - Advanced/14/en

8. Define the following terms:

a. Stipule

Outgrowths on either side of the petiole.

b. Petiole

A leaf's stem.

c. Blade

The flat portion of a leaf, the blade may simple or be divided into leaflets (compound).

d. Pitch

Pitch is the name for any of a number of highly viscous liquids which appear solid. Pitch can be made from petroleum products or plants. Pitch produced from plants is also known as resin.

e. Heartwood

Examination of the cross-section of a log will reveal dark wood near the center, and light-colored wood near the bark. The dark wood near the center is heartwood. As a tree increases in age and diameter an inner portion of the sapwood becomes inactive and finally ceases to function, as the cells die. This inert or dead portion is called heartwood.

f. Sapwood

Sapwood is comparatively new wood, comprising living cells in the growing tree. All wood in a tree is first formed as sapwood. Its principal functions are to conduct water from the roots to the leaves and to store up and give back according to the season the food prepared in the leaves.

g. Springwood

The inner portion of a growth ring is formed early in the growing season, when growth is comparatively rapid (hence the wood is less dense) and is known as "early wood" or "spring wood"

h. Summerwood

The outer portion of the growth ring is the "late wood" (and has sometimes been termed "summerwood", often being produced in the summer, though sometimes in the autumn) and is more dense.

i. Annual ring

Annual rings can be seen in a horizontal cross section cut through the trunk of a tree. Visible rings result from the change in growth speed through the seasons of the year, thus one ring usually marks the passage of one year in the life of the tree. The rings are more visible in temperate zones, where the seasons differ more markedly.

j. Cambium

A layer of cells just under the bark of a tree. This layer is only one cell deep, and it produces all the new wood in a tree.

k. Xylem

A vein in a tree that brings water from the roots into the leaf.

l. Phloem

A vein in a tree that moves sap out, the latter containing the glucose (a form of sugar) produced by photosynthesis in the leaf.