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Structure of tree

Tree basically consist of three parts i.e. trunk, crown, and roots. Function of trunk is to support the crown and to supply water and nutrients from the roots to the devices through branches and from leaves to the roots. Further subdivided in two parts:

1) macrostructure

The structure of wood , visible to naked eye or at a small magnification is called the macrostructure.

a) Pitch

  • Inner molt, central position or core of the tree is called the pitch or medullar
  • Vary in size and change for different trees

b) Heart wood

  • Inner annual rings surrounding the pitch constitute heart wood
  • Dark in colour and imparts rigidity to the tree

c) Sap wood

  • Outer annual rings between Heartwood and cambium layer is known as sapwood
  • It is light in weight and colour

d) Cambium layer

  • Thin layer of sap between  sapwood and inner bark is known as cambium layer
  • If the bark is removed for any reason, then the surface of exposed and cells cease to be inactive resulting in the death of tree

e) Inner bark

  • Inner skin or layer covering the cambium layer is known as the inner bark
  • Give protection to cambium layer from any injury

f) Outer bark

  • Outer skin or cover of tree is known as the outer bark
  • It is the outermost protective layer and contains cracks and failures

g) Medullary rays

The thin radial fibres extending from pitch to cambium layer is known as the Medullary rays

2) Microstructure

Structure of wood apparent only at great magnification is called Microstructure. It consists of dead and living cells of various  size and shapes
Cell membrane mainly consists of cellulose and cellular tissue cells

- Conductive cells
- Mechanical cells
- Storage cells

Conductive cells:- Transmit nutrients from roots to branches and leaves
Mechanical cells:- Imparts strength to the wood
Storage cells:- Cell serves to store and transmit nutrients from one to other living cells


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