*Identifies The Most Common Trees, With A Picture,Quick Reference Box And Informative Text For Each.
Illustrated Throughout With Superb Color Photographs.
Detailed Introduction Provides Infomation On How To Identify Trees, Their Distribution And The...
The tree's bark resembles armor or a protective skin, offering a waterproof protective layer against disease, water loss , insects , animals and even , in some cases, against forest fires. Bark allows the tree to breath, being perforated with minute breathing pores known as lenticels, which allow oxygen to pass into the tree. Lenticels can become blocked with pollution and certain trees shed and renew their bark, the London Plane is such a tree and is renowned for its ability to grow in polluted environment, hence its popularity as an urban street tree.
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Scrub Pine Pinus virginiana Trunk Bark
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Pine Tree Trunk Bark
The structure of tree bark
The cambium and its "zone" is a cell generator (reproductive tissue called growth meristem) that produces both the inner bark cells of the phloem and new living wood cells in the xylem. The phloem transports sugars from leaves to roots. The xylem is a transport tissue and both stores starch and conducts water and substances dissolved in water to leaves.
Phloem, or inner bark, develops from the outside layer of the cambium and is the food track to the roots. Sugars are transported from leaves toward roots in the phloem. When the tree is healthy and growing and sugars are abundant, stored food in the form of starch can be converted back into sugars and moved to where it is needed in the tree.
Xylem is living "sapwood" and located inside the cambial zone. The outer portion of xylem is conducting and storing starch in the symplast plus conducts water and substances dissolved in water to the leaves. The inner portion of the xylem is non-conducting wood that stores starch and is sometimes called heartwood. The major structures for water transport in xylem are vessels in angiosperms (hardwoods) and tracheids in gymnosperms (conifers).
Symplast is the network of living cells and the connections between living cells. Starch is stored in the symplast. Axial parenchyma, ray parenchyma, sieve tubes, companion cells, cork cambium, the cambium, and plasmodesmada make up the symplast.
Vessels (in hardwoods) and tracheids (in conifers) conduct water and substances dissolved in water. Vessels are vertically aligned tubes made up of dead cells that transport liquid. Vessels are found only in angiosperms. Tracheids are dead, single-celled "pipes" that act much like vessels but are only found in gymnosperms
