Re: [IAWA Forum] RE: Radial water transport

From: "John Barnett" <j.r.barnett@reading.ac.uk>
Subject: Re: [IAWA Forum] RE: Radial water transport
Date: Mon, 7 Oct 2002 17:28:11 +0100

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I think that Lloyd is right that there will be some radial shift of =
water as a result of pit distribution in tangential walls of conifers. =
This will be helped by the fact that tracheids often have tips which are =
displaced out of line with the rest of the cell, and most pits tend to =
be towards the tips. It also seems to me that where you have ray =
tracheids then these would allow radial transport. The situation with =
parenchyma is less clear.

I once, for fun, did a dye flow experiment with oak. I cut through the =
base of an oak sapling (in leaf) about 1.5 metres high and about 2cm =
diameter at the base and immersed the base of the cut stem in a jar of =
safranin. The day was hot and dry and followed a spell of hot dry =
weather, so one could imagine the plant was drought stressed. In the =
time it took me to walk back to the lab carrying the plant in the liquid =
(about five minutes), about 50ml of safranin had been drawn up. I =
refilled the pot of safranin and left the assembly for about fifteen =
minutes. I then started cutting back from the tips. Safranin had already =
reached the smallest twigs. I then cut back into the main stem, which =
was stained red everywhere except in the large multiseriate rays. This =
suggested to me that these rays play no part in water transport. The =
uniseriate rays did seem to stain. Of course, the question of radial =
transport did not arise as the whole base of the stem was immersed. I am =
unable to explain this observation. I was unable to repeat the =
experiment since the following day the "gardeners" at the University =
brashed out all the wild oak saplings which were apparently getting in =
their way!


John

Professor J.R.Barnett
School of Plant Sciences
The University of Reading
Whiteknights
Reading
RG6 6AS
UK

Tel. 01183 786162
Fax. 01189 753676

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<DIV><FONT face=3DArial size=3D2>I think that Lloyd is right that there =
will be some=20
radial shift of water as a result of pit distribution in tangential =
walls of=20
conifers. This will be helped by the fact that tracheids often have tips =
which=20
are displaced out of line with the rest of the cell, and most pits tend =
to be=20
towards the tips. It also seems to me that where you have ray tracheids =
then=20
these would allow radial transport. The situation with parenchyma is =
less=20
clear.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>I once, for fun, did a dye flow =
experiment with=20
oak. I&nbsp;cut through the base of an oak sapling (in leaf) about 1.5 =
metres=20
high and about 2cm diameter at the base and immersed the base of the cut =
stem in=20
a jar of safranin. The day was hot and dry and followed a spell of hot =
dry=20
weather, so one could imagine the&nbsp;plant was drought stressed. In =
the time=20
it took&nbsp;me to walk back to the lab carrying the plant in the liquid =
(about=20
five minutes), about 50ml of safranin had been drawn&nbsp;up. I refilled =
the pot=20
of safranin and left the assembly for about fifteen minutes. I then =
started=20
cutting back from the tips. Safranin had already reached the smallest =
twigs. I=20
then cut back into the main stem, which was stained red everywhere=20
<STRONG>except</STRONG> in the large multiseriate rays. This suggested =
to me=20
that these rays play no part in&nbsp;water transport. The uniseriate =
rays did=20
seem to stain. Of course, the question of radial transport did not arise =
as the=20
whole base of the stem was immersed. I am unable to explain this =
observation. I=20
was unable to repeat the experiment since the following day the =
"gardeners" at=20
the University brashed out all the wild oak saplings which were =
apparently=20
getting in their way!</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>John</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>Professor J.R.Barnett<BR>School of =
Plant=20
Sciences<BR>The University of Reading<BR>Whiteknights<BR>Reading<BR>RG6=20
6AS<BR>UK</FONT></DIV>
<DIV>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>Tel. 01183 786162<BR>Fax. 01189=20
753676</FONT></DIV></BODY></HTML>

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