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Transport In Plants

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Transport In Plants

Postby rightbraindominant » Wed Jan 28, 2009 12:13 am

What are the structural differences between the xylem vessel and the phloem tissue?
How are the structures of both, related to their respective functions?

These are two question i've been working on but I'm not sure If I have the right idea. Can anyone help me out?
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Postby mith » Wed Jan 28, 2009 4:20 am

what do you think?
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Postby mcar » Sun Feb 08, 2009 11:57 am

I remember observing a cross section of a corn old stem, xylem vessels are larger than phloem vessels.
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Postby kika » Tue Aug 02, 2011 10:40 am

The first answer to the question:
Both xylem and phloem are vascular tissues found in a plant. Xylem is a tubular structure which is responsible for water transport from the roots towards all of the parts of the plant. Phloem is also a tubular structure but is responsible for the transportation of food and other nutrients needed by plant. Xylem imports water and minerals while Phloem transports water and food. Xylem exists as non-living tissue at maturity, but phloem is living cells.
Xylem: Hard wall cells transport water and mineral nutrients
Phloem: Relatively soft -walled cells transport organic nutrients
"Hardness and softness" is a function of the amount of lignification and extractive content of the individual cell walls not there location in the tree.
Xylem:
It is a dead complex permanent tissue. Sapwood is xylem and mostly alive
It is the principal water conducting tissue of vascular plants.
Xylem consists of tracheids , vessels , xylem parenchyma and xylem fibres. Also ray parenchyma Also the xylem of softwoods (Gymnospermae) do NOT contain vessels.
Phloem:
It is a living complex permanent tissue. Inner phloem is alive. Outer phloem is dead.
It is the principal food conducting tissue found in vascular plants. Actually only the first .2-.7mm of the phloem is functional in food transport. The rest is non-functioning (ref. Esau's Plant Anatomy, 3rd ed. 2006, Chap.14) also (ALFIERI, F. J., and R. F. EVERT. 1968. Seasonal development of the secondary phloem in Pinus. Am. J. Bot. 55, 518-528.)
It consists of sieve cells , sieve tube elements , phloem parenchyma and phloem fibres. There are also phloem ray cells.
Xylem consists of the inner heartwood (the dead part) and the outer portion called the sapwood (the mostly living part.) Xylem "wood" from the Greek xylon. The actual transport of the water and minerals from the roots (sap) is carried out by the outer portion of the sapwood (nearest the bark).The largest percentage of the sap is transported in the first few growth rings.
The answer to the second question:
Structure refers to how the (body ) is put together-bones, muscles, tendons and ligaments - then onto organ structure, down to the cellular level-
Function refers to how (the body ) works,what does it do ?
example-structure of an organ- the largest in the human body - skin-
epidermis, dermis,layer of fat,etc.. function- regulates body temperature , expands to allow body movement, cools body temperature, houses nerve endings ,enabling to feel pressure or pain
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