BIOL 1011 Lecture Notes - Lecture 3: Cork Cambium, Vascular Cambium, Phloem
Secondary Growth, Transport and Photosynthesis I
January 20, 2015
Secondary growth begins after primary growth. This growth is responsible for the
diameter or width of the plant. Wood is a type of secondary growth which occurs om
conifers and eudicots.
The secondary meristem called vascular cambium arises from primary tissues
(especially procambium). Its function is to make secondary phloem to transport the
sugar water. Secondary xylem is essentially wood.
The primary phloem gets pushed out and stops functioning. The primary xylem gets
pushed into the middle, which it then also withers away. The secondary xylem and
phloem have completely taken over. The plant creates a cork cambium (another
secondary meristem) from the cortex to protect the plant and limit water loss. The
cork takes the place of the epidermis.
Overall, the Vascular Cambium:
• Produces secondary phloem to outside
• Produces secondary xylem to inside (aka wood)
• Increases its own circumference
The vascular cambium contains:
• fusiform initials
o to make tracheids and/or vessel elements
o to make sieve elements (phloem)
• ray initials
o makes rays
In oak, there are lignin in secondary walls of tracheids and vessel elements.
Everything outside the vascular cambium is bark.
Cork Cambium
• new lateral meristem
• arises from cylinder of cortex cells outside vascular cambium
• Produces:
o Phelloderm to inside (thin layer of parenchyma cells)
o Cork to outside
▪ Suberized, dead cells
▪ Protects woody plant (there is no more epidermis)
Periderm = cork cambium + cork
* See tissues of woody stem diagram
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Document Summary
This growth is responsible for the diameter or width of the plant. Wood is a type of secondary growth which occurs om conifers and eudicots. The secondary meristem called vascular cambium arises from primary tissues (especially procambium). Its function is to make secondary phloem to transport the (cid:498)sugar water(cid:499). The primary phloem gets pushed out and stops functioning. The primary xylem gets pushed into the middle, which it then also withers away. The secondary xylem and phloem have completely taken over. The plant creates a cork cambium (another secondary meristem) from the cortex to protect the plant and limit water loss. The cork takes the place of the epidermis. Overall, the vascular cambium: produces secondary phloem to outside, produces secondary xylem to inside (aka wood) The vascular cambium contains: fusiform initials: to make tracheids and/or vessel elements, to make sieve elements (phloem, ray initials, makes rays. In oak, there are lignin in secondary walls of tracheids and vessel elements.
