METHOD FOR THE GENTLE ISOLATION OF AQUATIC PLANTS WHICH FLOAT ON THE WATER

METHODE POUR CUEILLIR EN DOUCEUR DES PLANTES AQUATIQUES FLOTTANT A LA SURFACE DE L'EAU

English Abstract

The invention relates to a method for the gentle isolation from
ponds, basins or containers of aquatic plants which float on the
water. The process according to the invention comprises
a) generating, on the water surface in the pond, basin or
container, a flow which is directed toward the site of
withdrawal, which drives the aquatic plants toward the
site of withdrawal,
b) withdrawing the aquatic plants individually at the site
of withdrawal from the pond, basin or container by means
of a hydrophilic solid or liquid medium, and
c) transferring the aquatic plants individually into
containers.

French Abstract

La présente invention a pour objet une méthode permettant d'isoler et de cueillir en douceur des plantes aquatiques flottant à la surface d'étangs, de bassins ou de réservoirs. La méthode visée par les présentes comporte les étapes suivantes : (a) création, à la surface de l'étang, du bassin ou du réservoir, d'une circulation d'eau dirigée vers un lieu de cueillette désigné vers lequel les plantes sont entraînées; (b) prélèvement individuel des plantes parvenues au lieu de cueillette désigné à la surface de l'étang, du bassin ou du réservoir au moyen d'hydrophiles sous forme solide ou liquide et, (c) transfert individuel des plantes dans des contenants.

Claims

6
We claim:
1. A method for the gentle isolation from ponds, basins or
containers of aquatic plants which float on the water, which
comprises
a) generating, on the water surface in the pond, basin or
container, a flow which is directed toward the site of
withdrawal, which drives the aquatic plants toward the
site of withdrawal,
b) withdrawing the aquatic plants individually at the site
of withdrawal from the pond, basin or container by means
of a hydrophilic solid or liquid medium, and
c) transferring the aquatic plants individually into
containers.
2. A method as claimed in claim 1, wherein the directed flow is
generated by immersing one or more hydrophilic solids into
the water and moving it or them out of the water toward the
site of withdrawal at a speed at which the surface of the
water film which wets the hydrophilic solid is retained as
long as possible.
3. A method as claimed in claim 1 or 2, wherein the hydrophilic
solids are threads, tapes, rods poles, endless loops
or rotating disks.
4. A method as claimed in claim 3, wherein the hydrophilic solid
used is an endless loop made from hydrophilic or
surface-hydrophilized elastomer.
5. A method as claimed in claim 4, wherein the hydrophilic or
surface-hydrophilized elastomer is selected from the group
consisting of ethylene/propylene rubber which has been
modified by irradiation-induced grafting of acrylic acid,
hydrophilic polyvinyl siloxane, polyethylene or polymethyl
methacrylate which has been surface-modified by oxidation
with chromic acid solution or by hot-pressing between Teflon®
slabs, polyethylene which has been surface-modified with
nitrogen oxide plasma, hydrophilic polyurethane/urea
elastomer with ethylene oxide and tetramethylene oxide
groups, hydrophilic polyether elastomer, or polypropylene

7
which has been hydrophilized by plasma graft polymerization
of glycidyl methacrylate.
6. A method as claimed in claim 1, wherein the directed
flow is generated by expelling water jets toward the site
of withdrawal from one or more nozzles arranged beneath the
water surface.
7. A method as claimed in claim 1, wherein the directed
flow is generated by placing a suction device at the site
of withdrawal beneath the water surface and drawing water
toward the site of withdrawal.
8. A method as claimed in any one of claims 1 to 7,
wherein the aquatic plants are withdrawn from the ponds,
basins or containers at the site of withdrawal by means of
hydrophilic solids, by immersing the solids into the water
and removing them from the water at a speed at which the
plants adhere to the solids individually.
9. A method as claimed in any one of claims 1 to 7,
wherein the aquatic plants are transferred individually
from the ponds, basins or containers at the site of
withdrawal by means of a water jet expelled from a nozzle
which is arranged beneath the water surface.
10. A method as claimed in any one of claims 1 to 7,
wherein the aquatic plants are drawn individually from the
ponds, basins or containers by means of a suction device
which is placed beneath the water surface.
11. A method as claimed in claim 1, wherein, after
detection by means of a light barrier and subsequent

8
transfer into individual containers by means of an air or
water jet, the aquatic plants which have been withdrawn are
isolated.

Description

CA 02243002 1998-08-24
Method for the gentle isolation of aquatic plants which float on
the water
The invention relates to a method for the gentle isolation from
ponds, basins or containers of aquatic plants which float on the
water.
A~atic plants which float on the water (free-floating plants),
for example Lemna species, Azolla species and Salvinia species,
float on the water surface with their leaves while their roots,
which, depending on the species, have different shapes, protrude
into the water. In ponds, storage basins or nursery basins, these
Plants may form dense layers made up of many thousand
individuals. Free-floating plants are very important as test
systems for investigations in the fields of crop protection and
plant genetics since a large number of them can be grown in
confined spaces, since they live in a medium whose composition is
easy to control and to manipulate (water) and since, in addition,
their symbiosis with species of Cyanobacteria such as Nostoc and
Anabaena, for example in the leaflets of Azolla species, they
have developed a method of storing nitrogen which, if possible,
should be made exploitable for genetic engineering purposes.
30
For experimental purposes it is necessary to transfer the
individual plants into test containers, which has been carried
out manually until now and entails substantial personnel and thus
also financial input.
DE-A-44 25 522 discloses the separation of free-flowing bulk
materials, for example wheat, with the aid of a belt-type cell
selector, thus achieving higher throughput in comparison with
cylindrical sorting and cleaning devices.
GB-B-2 184 033 discloses an apparatus which allows an improved
mechanization when examining small test volumes by liquid
chromatography by means of a shaped conveyor belt.
The conveyor belts used are neither hydrophilic nor is mention
made of their use for the isolation of free-floating plants.
It is an object of the present invention to mechanize and/or
automatize the isolation, and separation into individual units,
of free-floating aquatic plants.

CA 02243002 2002-05-07
Surprisingly, it has been found that aquatic plants adhere more
strongly to wet surfaces than t0 each Other. Surprisingly, it has
also been found that aquatic plants can be separated from each
other by suction or by water jets of a specific power.
The present 'invention therefore relates to a method for the
gentle isolation from ponds, basins or containers of aquatic
plants which float on the water, which comprises
a) generating, on the water surface in the pond, basin or
container, a flow which is directed toward the site of
withdrawal, which drives the aquatic plants toward the site
of withdrawal,
b) withdrawing the aquatic plants individually at the site of
withdrawal from the pond, basin or container by means of a
hydrophiilic solid or liquid medium, and
e) transferring the aquatic plants individually into containers:
In a preferred embodiment of the process according to the
invention, the directed flow described in a) is generated by
immersing one or more hydrophilic solids into the water and
moving it or them out of the water toward the site of withdrawal
at a speed at which the surface of the water film which wets the
hydrophilic solid is retained as long as possible.
Hydrophilic solids for the purposes of the present invention are
those solids which are wettable by water.
Hydrophilic solids which are especially suitable in accordance
with the invention are, for example, threads, tapes, rods or
poles, in particular endless loops or rotating disks made of
thoroughly wettable materials, in particular endless loops made
from hydrophilic or surface-hydrophilized elastomers. Hydrophilic
or surface-hydrophilized elastomers which can be used in
accordance with the invention are, for example,
ethylene/propylene rubber (EPR) modified by irradiation-induced
grafting of acrylic acid (known from Soebianto, Y.S. et al.,
Angew. Makromol. Chem. (1987) 152, p. 149 - 158), hydrophilic
polyvinyl siloxanes (known from Bader, F. and Setz, J., Dent.
Lab. (1992) 40/3, p. 421 - 423), polyethylene or polymethyl
methacrylate which has been surface-treated by oxidation with
chromic acid solutions or by hot-pressing between Teflon~slabs
I~o~ from Wang, R.-H. and Stoffer, J.O., Polym. Mater. Sci.
Eng. (1992) 67, p. 123 - 124), polyethylene which has been
surface-modified by treatment with nitrogen oxide plasma (known

CA 02243002 1998-08-24
3
from Inagaki, N. et al., Appl. Polym. Symp. (1990) 46, p. 399 -
413), hydrophilic polyurethane/urea elastomers with ethylene
oxide and tetramethylene oxide groups (known from Dror, M. and
Stewart, M., Annu. Tech. Conf. Soc. Plast. Eng. (1990), p. 1132 -
1134), hydrophilic polyether elastomers (known from Shih, J.S.
and Tirrell, D.A., J. Polym. Sci., Polym. Chem. Ed. (1984) 22/3,
p. 781 - 791), polypropylene which has been hydrophilized by
means of plasma graft polymerization of glycidyl methacrylate
(known from Inagaki, N. et al., Polym. Bull. (1991) 26/3, p. 283
- 289) and polyethylenes which have been surface-modified by
introducing amide or ester groups (known from Wilson, M.D. et
al., J. Am. Chem. Soc. (1990) 112/3, p. 1244 - 1245). Other
processes for the preparation of hydrophilic or
surface-hydrophilized elastomers which are suitable in accordance
with the indention are known from Rreiner, C.F., Technical
Lecture WVAO Annual Conference (1985), p. 148 - 156.
If such a hydrophilic solid is pulled out of the water, a film of
water forms on its surface. This process simultaneously generates
a flow on the water surface toward the hydrophilic solid, This
flow causes objects which float on the water surface, for example
free-floating plants, to move toward the hydrophilic solid. The
result is that the free-floating plants eventually come into
contact with the hydrophilic solid and, due to adhesion, adhere
to the hydrophilic solid together with the film of water when the
hydrophilic solid is pulled out of the water. A condition is that
the speed with which the solid is immersed into the water and
pulled out of the water allows the film of water located on the
solid to remain stable as long as~possible. This is why it is
advantageous to move the solids only slowly, preferably at a
speed of 0.5 to 500, in particular 5 to 300 mm/s, especially
preferably 10 to 50 mm/s.
The use of rotating disks and, in particular, endless loops made
from hydrophilic elastomer is especially preferred since the
free-floating plants can be withdrawn from the water continuously
if the arrangement and speed are suitable. Such an endless loop
is shown, for example, in Figure 1, where W denotes aquatic
plants, B a basin and E an endless loop.
A further preferred embodiment of the process according to the
invention consists in generating the directed flow described in
a) in such a way that water jets are expelled toward the site of
withdrawal from one or more nozzles arranged beneath the water
surface. The diameter of the nozzles, and the pressure of the
water jets produced by them, can be varied within a wide range to

CA 02243002 1998-08-24
4
suit the shape, size and mass of the plants to be separated into
individual units. Typically, the nozzle diameter is approximately
0.05 to 5 mm, in particular approximately 0.1 to 2 mm. The outlet
pressure of the water jet flowing from the nozzle is, as a rule,
at approximately 0.5 to 5 bar, in particular approximately 2 to
3 bar.
The nozzles used for generating the flow can expediently also be
used for the separation of the aquatic plants into individual
units, as described in b). Ideally, the nozzles, which are
arranged beneath the water surface at the site of withdrawal and
which remove the aquatic plants from the water individually, are
fixed at an angle of approximately 45° relative to the water
surface. Nozzle diameter and water pressure should be as
described above. The water level should be kept constant, for
example by means of a control circuit.
A further preferred embodiment of the process according to the
Invention consists in generating the directed flow described in
a) by placing a suction device at the site of withdrawal beneath
the water surface and drawing water toward the site of
withdrawal. The plants which float on the water surface thus
drift toward the site of withdrawal. The aquatic plants can then
expediently be drawn out of the water individually at the site of
withdrawal by means of the suction device placed beneath the
water surface. In principle, this may also be effected parallel
to the water surface or directly on the water surface. However,
when the plants are removed from the water surface, the air which
is also drawn in interferes with the detection of the plants for
the subsequent and necessary separation step. Drawing-off can be
effected with customary pumps, for example with electrically
operated suction pumps. A prerequisite for this procedure is an
exact control of the water level and of the drawing-off rate.
In principle, each of the methodological steps according to the
invention for generating the flow can be combined with each
methodological step in accordance with the invention for
withdrawing the aquatic plants. However, it is generally
Preferable to carry out the withdrawal with the same devices with
which the flow had been generated, since the equipment is less
complicated.
After detection, for example by means of a light barrier
(capacitive or inductive method) and subsequent transfer into
individual containers by means of an air or water jet, the the

CA 02243002 1998-08-24
S
aquatic plants which have been withdrawn in accordance with the
invention can now be isolated.
The examples which follow illustrate the invention without
limiting it thereto:
Example 1
Approximately 100 Lemna plants are grown in a 5-1 glass container
containing 4 1 of water. An elastomer tape according to the
invention of 2 mm width is drawn through the water at a speed of
10 - 50 mm/sec by means of an electric motor. The plants are thus
withdrawn from the water individually on the elastomer tape and
can be flushed individually into containers using a water jet.
Example 2
Approximately 100 Lemma plants are grown in a 5-1 glass container
containing 4 1 of water. Approximately 3 mm beneath the water
surface, a hollow needle with an outlet opening 0.2 mm in
diameter is fixed so that it points upwards at an angle of
approximately 45~, and a water line with a pressure of
approximately 3 bar is connected to the hollow needle. The Lemma
plants move toward the water outlet and are transported
individually out of the glass container together with the water
jet.
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Representative Drawing