Since herbaceous plants usually live for only one season (annuals and biennials) and woody  plants may live several seasons (perennials),  young herbaceous plant may only contain primary xylem and phloem which was derived from the primary meristem (procambium).
 
 

Plants that live  many seasons must be able to produce new xylem and phloem each season. This process is accomplished by a  vascular cambium which forms between the primary xylem and phloem (meta xylem and phloem).

                             Ferns - absent
                             Gymnosperms - present
                             Dicots – present in woody – absent in many herbaceous
                             Monocots – absent

The vascular cambium produces secondary phloem to its outside and secondary xylem to its inside.  This process is called secondary growth. Also near the outside of the stem the outer cortex cells may become meristematic and form a cork cambium which produces cork to the outside.

The growth of both of these cambiums is
responsible for the increase in width of a plant.

  Fascicular cambium – provascular bundle
  Interfascicular cambium – pith
 

Refer to figures in text book.
 
 
 
 
 
 
 
 
 

Secondary Xylem – Wood

Hardwood contains many fibers - Oak

Softwood contains fewer fibers - Pine
 

Annual Rings – late  wood alternates with early wood

Heartwood dead stores non-usable minerals.

Sapwood outer part is alive

Secondary Phloem –  phloem nearest cambium is functional
 

Cork cambium or phellogen
 
 
 

Refer to figures in text book.
 

Periderm includes cork cambium, cork,
 

Lenticles allows bark to be permeable to oxygen
 
 
 

Roots have secondary growth
 
 
 

Refer to figures in text book.
 
 

Place the following tissues in the correct order starting from the inside moving to the outside  of a woody stem. cortex, epidermis, cork, cork cambium primary xylem, primary phloem,  secondary xylem, secondary phloem, vascular cambium, pith.

Where in a stem is the older xylem?

   How does secondary growth produce annual rings in temperate areas?

Refer to figures in text book.

Using the text draw a figure showing secondary growth of a three year old woody stem. Include the following:  cortex, epidermis, cork, cork cambium primary xylem, primary phloem,  secondary xylem, secondary phloem, vascular cambium, pith.
 
 
 
 

  WOOD,  BARK, KNOTS

The wood of a tree consists of everything to the inside of the vascular cambium and the bark consists of everything to the outside of the cambium.

Knots are lateral branches where the trunk of the tree has grown around these organs.
 
 

   From which tissues is wood formed?

   From which tissues is bark formed?

   A nail is placed in a tree five feet from the ground. Explain the position of the nail ten years later.  Include  both the location of the nail in length from ground and position in the trunk.

Summary of plant tissue derivation:

Apical meristem (meristematic)  forms three meristems (protoderm, ground meristem and procambium). The procambium forms the primary xylem, primary phloem and the vascular cambium.

The vascular cambium produces secondary xylem and secondary phloem. Xylem is produced to the inside of the cambium and phloem is produced to the
outside of the cambium.

The outer cells of the cortex may become meristematic and form a cork cambium. The cork
cambium produces cork to its outside.