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FLOATERS-All you wanted to know about (?)

P. Rocha P.S.C.F.Rocha at durham.ac.uk
Tue May 18 10:52:59 EST 1999

Dear All,

Thank you to all who have taken time to give me some advice on "floaters"
(for Arabidopsis plants).
Due to "popular demand" I am hereby making those replies available along
with some of my own comments. My sincere apologies to all those interested
in the answers for the delay in posting this.

1. polystyrene
I have in the past used "styrofoam" (polystyrene) racks for 1.5 ml
centrifuge tubes for the proposed aim. The material can be surface
sterilized (but the use of a detergent is probably recommendable as a
result of the formation of air pockets on the surface).

Dr. E. Kinsman (Roehampton Institute London) uses the same sort of
"I'm only aware of people making their own floaters. I used to use
polystyrene ceiling tiles (available from DIY stores), cut to size.  I
punched holes through using a cork borer.  These wouldn't be

[Actually the material can survive one cycle of autoclaving with
considerable shrinking and the release of (probably not very healthy)

Difficulties arise when using this material for large-scale experiments
involving growth under sterile conditions (cutting "styrofoam" to size and
making holes is only fun if you enjoy playing with a red-hot knife and the
resulting fumes-this will also make you very popular in your lab; Of
course, someone had the bad idea of inventing fumehoodsbut the problem of
sterilizing remains. The ideal floater should withstand autoclaving so
that it could be sterilized in the containing vessel and avoid extra
trouble and chances of re-contamination-hence my question.

2. The really expensive option:

Dr. Christa Lechelt-Kunze (Bayer, FRG), Prof. David Oppenheimer and Prof.
Timothy Short (Queens College, CUNY) suggest use of "The floater inserts
for Magenta boxes (sold both by Life Technologies and Sigma) work very
well, are autoclavable and reuseable, and have numerous options for
different species.  The downside is the ridiculously high prices."

Indeed they are, I've checked. Catalogue numbers include, among others, M
4417; Z35,850-9; Z35,851-7; M 7288

3. Of general application:

I thank Mary Lai (U.C. Davis) for her detailed suggestion which can be
applied to all sorts of plants big and small.

"I have grown many plants hydroponically, using household materials.  One
method is to grow the plants on cheesecloth, supported by chicken wire.
Cut out a sheet of chicken wire about the size of the tub or pot you are
using (I like using the large Nalgene autoclave tubs), put supports
underneath to raise the chicken wire off the floor of the tub.  For
supports, I've used small strips of chicken wire bent into a U-shape.
Beakers also work.  Lay one or two layers of cheesecloth over the chicken
wire, with the sides hanging down into the liquid solution.  Make sure the
level of the liquid underneath is not too high (to drown the plants) and
not too low (so the plants dry out before they reach the liquid).  I then
level of the liquid underneath is not too high (to drown the plants) and
not too low (so the plants dry out before they reach the liquid).  I then
spread my seeds over the top of the cheesecloth and cover the whole tub
with plastic wrap to help germination.  After germination, the roots will
grow through the cheescloth down towards the liquid, leaving the aerial
parts above.  I remove the Saran wrap about a day after germination.
Also, aeration of the liquid solution is necessary, so I bubble air into
it. This method has worked with roots as large as peas.  It's very simple
to harvest the roots:  just turn the chicken wire over (so that the roots
are in the air) and use a razor or scissors to cut them off.  When I'm
done, I just toss the tub and chicken wire into the autoclave together.

If you are growing plants on a small scale, I've used pipette tip boxes
also.  Convenient holes with a reservoir underneath."

4. Foam: the nearly perfect solution

>From the group of Dr. M. Hawkesford and also Dr. Jon Shaff (Cornell U.)
comes the suggestion of use of polyethylene foam:

"in the past we have used a material from a company called " nalgene"
which is basically 3 or 6mm thick polyetheylene foam sold in sheets or
rolls. it can be cut to dimension and holes can be made to accommodate
plants. it definitely floats. however, it can not be autoclaved. one could
ethanol, gas or bleach sterilize it. nalgene refers to the item as " clean
sheetswork surface (catalog no. 6281 and 6283).
check out the items at the nalgenunc web site: http://www.nalgenunc.com"

(J. Shaff)

In the UK a similar polyethylene-based material can be obtained from RS
supplies (electr-ic -onic equipment supplier; http://rswww.com/). Their
catalogue numbers and prices are:
303-2274 (3 mm); 303-2280 (6 mm); 303-2296 (10 mm); all with surface area
of 2 m2 (yes, meter sq) for between 12.00-28.00!!

5. The perfect solution

Is a similar foam to 4. but that can withstand autoclaving. I know it
exists, somewhere, just waiting to be found.


P.S. Thank you to all those who replied in Spanish (but I'm afraid
I am one of the 190,000,000 who speak Portuguese).
P. Rocha
Dept. of Biological Sciences
University of Durham
South Rd.
Durham, DH1 3LE


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