Bark: the protective outside covering of a woody stem or root.
Cambium: thin layer of living cells that produce a new layer of wood each year, forming tree rings, which we can count to tell the age of a tree. Th e cambium lies between the xylem and phloem layers.
Carbon Dioxide: a colorless, odorless gas that is formed during respiration, combustion, and organic decomposition.
Cellular Respiration: the chemical breakdown of glucose to produce energy. This process is the opposite of photosynthesis.
Chlorophyll: the green substance found in leaves and needles that captures the sun's energy.
Heartwood: the hard, inactive wood at the center of the tree.
Oxygen: an element found freely in nature that is needed for humans and animals to be able to breathe and is necessary for nearly all combustion to occur.
Phloem: layer of inner bark cells that transport food made by photosynthesis in the leaves to the rest of the plant.
Photosynthesis: the process of channeling energy from the sun by means of chlorophyll and converting the carbon dioxide in the air to produce nutrients for the tree and oxygen that is released into the atmosphere.
Roots: the network below ground that anchors the tree in the soil. Root hairs push their way through the soil and absorb moisture and minerals from the soil.
Sapwood: newly formed wood cells that lie just inside the cambium. It acts as a major conductor of water and minerals for the tree; also known as xylem.