about plants anatomy

[rama soujanya]

hi im soujanya
im having a doubt in the internal structure of a plant

through the phloem the food is conducted
it has sieve tube elements
arrow: on attaing maturity it losses its nucleus
but we believe that all living cells must have a nucleus
though that is a living cell it doesnt have any nucleus in the adult condition
pls solve my problem

[Linn]

well because at maturity the function is support ?:)
Lynne


edit: bTW this should be in botany forum

[Poison]

Let me answer your question with a question.
Do your RBCs have nucleus when they are mature?

[Linn]

BTW
that is a good question.


I also have trouble understanding this.
Only theory is that the companion cells that do have a nuclei, act
to control the seive cells.
I will do some searching on line and see what I can find.
Lynne

Poison: I dont know what you mean by RBC's?

something to do with plants?

I dont want to sound stupisd but in med terms that is red blood cells
and have no nucleous when mature so that there is more room to transport haemoglobin.
Do you mean that without nuclei the sieve tubes have more room to transport sugars?

[Navin]

Yes, I am sure that Poison was refering to Red Blood Cells.

[Poison]

I was trying to make you think about the theory that says:

but we believe that all living cells must have a nucleus
though that is a living cell it doesnt have any nucleus in the adult condition

Living cells have nucleus. But they can lose their nucleus when they are specialized for a job.

[2810712]

i understand this but one thing-
is that room really useful/ imp enough to replace nucleus.. i think no...
rather nucleus is rather useless in RBCs...



hrushikesh

[BLaZe]

The phloem contains sieve tubes made up of elongated cells that have lost thier nucleus and most of thier cytoplasmic organelles,. the transverse cell walls are perforated and thus ensure connection between two neighboring cells . the series of the stacked cells from a long sieve column . in addition to sieve tubes , the phloem contains companion cells next to the sieve tubes that are connected transversally with them by the plasmodesmata.Companion cells move sugars and amino acids into and out of the sieve elements.
the sieve tubes are considered to be living cells because they communicate with the companion cell that contains a nucleus, communication is done by the plasmodesmata.


Please click on download to see the picture.

[Linn]

but we still need a control tower somewhere to direct things.
Dont we? some cells can function w/o nuclei, but they are subject to chemical signals from other cells with nuclei?
that is what companion cells job is?

what about prokaryote cells? did I spell that right?
how do they function?

[Linn]

sorry Blaze
just realize basicaly same thing as you said.
communication via plasmoda