Protection Wood  - Protection wood is wood that no longer has any living symplast cells, and has been altered to a state that is more protective than the sapwood.  When wounded, sapwood has a dynamic response because of living cells.  When protection wood is wounded, chemically altered substances in the cells and cell walls resist the spread of infections.  Protection wood has many features that resist infection by decay-causing microorganisms.  As cells age and die in some species, the cell walls and lumens are impregnated with substances that impart a protective feature to the wood.  These substances are called extractives because they can be extracted from the wood by using various solvents.  Discolored wood or rather, color altered wood, Wetwood, Heartwood, and False Heartwood are the four basic types of protection wood.  The great difficulty with this subject is that all gradations of all four types of protection wood may be in the same trunk.  It is also possible to have discolored heartwood (normal heartwood that has later been discolored) and wetwood heartwood (normal heartwood that has later become wetwood).  The only way to understand these types of altered wood is to study them from longitudinal radial dissections. Central columns of "true" heartwood will be a uniform width throughout the trunk.  Other types of altered wood will have an entry point such as wounds or branch stubs.  Great confusion has come to this subject because only cross sections of wood have been studied, and any type of wood darker than the sapwood has been called heartwood or a type of heartwood.

Click here for more on heartwood (oaks). 

Also see "heartwood". 

Click here for more on color altered wood. 

Also see "discolored wood".

Also see "false heartwood".

Also see "wetwood".  

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