Vascular Plant Bodies

Water and nutrients flow through vascular plant tissues. Tissues are divided into two parts: xylem and phloem. The xylem is located close to the center of the plant; it transports water. A well-known example of xylem is wood, which is how vascular bodies transport water and nutrients to the tops of trees. Also, the xylem consists of dead cells. The phloem, on the other hand, consists of living cells. The phloem is located close to the outside of the plant. The purpose of the phloem is to move organic substances to the upper reaches of the plant.

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Trees depend largely on phloems because if you remove a circular layer of bark around the circumference then the tree will die. In leaves, the xylem is located on top and the phloem is located on the bottom. The vascular cambium is a layer located between the phloem and the xylem. The purpose of the vascular cambium is that it is the source of stem cells that differentiate into the phloem and the xylem. The amount of available sunlight and nutrients determines the growth rate of these cells. Growth patterns are determined by looking at the rings found in the tree trunks.

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A xylem includes tracheary elements. At maturity, they are dead and the elements have secondary walls. These also always have pits. A tracheid is a tracheary element with only pits. If a tracheary element also has perforations, then the tracheary element is called a vessel element. For example, conifers have tracheids but flowering plants have both tracheids and vessel elements.


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Sieve elements make up a phloem. The sieve elements are actually alive at maturity, but are always simplified because their nuclei, vacuole and other cell stuctures degenerate. In order to survive, the sieve elements need a life-support partner cell. All sieve elements have pores to connect to adjacent sieve elements. Sieve-tube elements are the ones that are restricted to certain walls shared by vertically arranged elements and sieve-tube elements also always have companion cells for the life support partners. In real life, sieve-tube elements are found in flowering plants. However, the sieve elements found in conifers are called sieve cells. These life support partners are in constrast called albuninous cells.




http://www.youtube.com/watch?v=35vPjdTNRU0
This video explains the process of vascular plant reproduction through a song.

Questions:
  1. Why do trees depend on phloems?
  2. The vascular cambium is located between:
  3. phloem and xylem
  4. soil and root
  5. plant and air
  6. What determines the growth rate of vascular cells?
  7. amount of available sunlight
  8. how many cells
  9. the size of the cells
  10. Contrast xylem and phloem.






Sources: http://www.wisegeek.com/in-plants-what-is-a-vascular-system.htm
http://botit.botany.wisc.edu/botany_130/Anatomy/Glossary/Vascular-Tissue-System.html