cross section of a trunk![click to hear](/images/speaker.jpg)
Moving from the center to the periphery there are six parts: the pith, the heartwood, the sapwood, the cambium, the phloem and the bark.
heartwood ![click to hear](/images/speaker.jpg)
Hard dark-colored wood layer made of dead sapwood; it encircles the pith and supports the trunk and branches.
pith ![click to hear](/images/speaker.jpg)
Central part of the trunk, composed of soft tissue that contains nutrients essential for sapling growth.
bark ![click to hear](/images/speaker.jpg)
Tree’s external protective layer; its texture and color vary depending on the species.
phloem ![click to hear](/images/speaker.jpg)
Tissue located immediately below the bark, whose main function is to transport sap transformed by photosynthesis from the leaves throughout the rest of the tree.
cambium ![click to hear](/images/speaker.jpg)
Growth tissue that simultaneously produces the external phloem and the internal sapwood, thereby enabling the tree to increase in diameter.
sapwood ![click to hear](/images/speaker.jpg)
Relatively new layer of wood that is generally pale in color; it transports raw sap, composed of water and nutrient minerals, from the roots to the leaves.
annual ring ![click to hear](/images/speaker.jpg)
Each of the concentric circles representing the layer of wood produced in one year; the age of the tree can be determined by the number of rings.
wood ray ![click to hear](/images/speaker.jpg)
Conduit connecting the pith to the core and circulating nutrients horizontally within the trunk.