Image Source - TREES, ASSOCIATES, and SHIGO (2 CD set).

Woody Roots  - Woody roots are organs that mechanically support the tree, store energy reserves, and transport liquids that contain many types of soluble substances.  More on woody roots:  Woody roots have lignin along with cellulose and hemicelluloses in their cell walls.   Woody roots have an outer bark that contains suberin.  Suberin gives bark its corky characteristic. Suberin "waterproofs" the tissues.  Woody roots have secondary growth.  Woody roots contain meristematic points.  Woody roots usually grow outward and downward.  New woody root tissues begin to grow soon after woody growth starts in the trunk.  Woody roots on most trees do not have a pith.  Woody roots usually store more energy reserves than stems.  Woody Roots have less lignin than woody stems which have an abundance of lignin.  Woody roots transport free water, and the substances dissolved in it, and synthesis substances such as growth regulators, amino acids and vitamins that are essential for growth.  They also hold water in the form of bound water.  They also contain more lignin than non-woody roots.  With respect to energy, woody roots are storage organs. As energy storage is depleted, opportunistic pathogens attack. Most root diseases start when root defense, which is based on energy storage, is low.  Meristematic points are sheets of radial parenchyma that extend from the wood into the outer bark.  The points have the capacity to form sprouts, flowers, woody roots, and prop roots.  The pith on woody roots is to the down side (most of the time).  Click here for more on woody roots. 

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