Journal of Environmental Quality 31:697-699 (2002)
© 2002 American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America
SHORT COMMUNICATIONS
A Time-Saving Method for Higher Plant Tests in Hydroculture
Cornelia Andersohn*,
Maike Fuchs,
Regina Seyed-Mansouri,
Susanne Fleischmann and
Berndt-Michael Wilke
Institut für Ökologie, Fachgebiet: Abfallbelastung der Landschaft, Technische Universität Berlin, Sekr. AT 3, Albrecht-Thaer-Weg 4, D-14195 Berlin, Germany
* Corresponding author (Cornelia.Andersohn{at}tu-berlin.de)
Received for publication April 23, 2001.
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ABSTRACT
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For higher plant tests in hydroculture we developed a method to unify the usually separately performed germination and growth testing. This method renders unnecessary the time-consuming and laborious installation of the germinated plants into the growth system.
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INTRODUCTION
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HIGHER plants are an essential part of the terrestrial biocenosis and are therefore a useful tool for testing the terrestrial ecotoxicity of hazardous liquid products that may be present in soil (Füll et al., 2000). Testing effects of liquid materials that strongly sorb to soil on plants (i.e., dissolved humic substances) makes it necessary to use hydroculture systems instead of soil pots. Germination is usually performed in petri dishes (
mídová, 1960; Fialová, 1969; Senesi and Loffredo, 1994; Loffredo et al., 1997). Attempts to unify the steps of germination and growth testing have already been made by Lüssem and Rahman (1980), who used a sieve as a plant carrier, and by Brunner et al. (1996), who developed a method similar to ours. They used a polyester net with styrofoam floats on each side as a plant carrier. For our studies, we used a nonsterile medical gauze instead. The gauze as a carrier material was already used for growth testing by mídová (1960), but she was still using petri dishes for germination. mídová did not recognize the potential of gauze as a self-threading medium for germinating seeds, but also may not have had access to Styropor (BASF, Ludwigshafen, Germany) or other floating material.
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Materials and Methods
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We poured 200 mL of distilled water into a 250-mL beaker. We then dispersed a layer of 300 mg of Styropor pellets of 3 to 6 mm in diameter per beaker on top of the water. We cut the gauze into a size that covered the beaker, and put it on the Styropor pellet layer (see Fig. 1a, 2a)
. The gauze that we used was a medical gauze (No. 304134/5) composed of 60% viscose and 40% cotton, purchased from Paul Hartmann AG (Heidenheim, Germany). If small seeds are used, for example cress (Lepidium sativum L.), vegetable turnip (Brassica rapa L. subsp. rapa), Chinese cabbage [Brassica rapa L. subsp. chinensis (L.) Hanelt], or sorghum [Sorghum bicolor (L.) Moench], 20 seeds are distributed evenly over the gauze (see Fig. 2a) and the beaker is covered with a watch glass (Fig. 1a and 2a). During the germination the gauze is used as a floating bracket in a beaker. The gauze is supported by the Styropor pellets. After germination the number of plants is reduced to the most homogenous 12 plants, of which 10 are evaluated. If bigger seeds are used, for example oat (Avena sativa L.) or barley (Hordeum vulgare L.), only 10 seeds fit into a beaker and should be reduced to seven plants per beaker after germination, of which five plants are evaluated. The gauze with all germinated plants on it is taken out of the distilled water and easily transferred into a beaker prepared with about 300 mL of test solution (see Fig. 2c) by extending the gauze. The gauze is then tightened with rubber bands onto the beaker and covered with a germination bell (Fig. 1b and 2c). The roots are given 1 cm of air between the gauze and the test solution for aeration (see Günther et al., 1993 and Fig. 1b). From the germination until the end of the test the beakers are kept under controlled conditions in a phytotron. We maintained 22°C for 16 h of light for the day period and 16°C for 8 h for the dark period. We covered the beakers in order to prevent desiccation of roots and plants. If a water saturation of 65 to 80% of the air can be provided by the phytotron the covering will be unnecessary. The test duration is at maximum 7 d. If a longer period is required, the test solution needs to be changed weekly.
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Fig. 2. (a) Set up for germination. (b) Germinated turnip plants at the end of the germination phase. (c) Start of the plant growth test in the test solution.
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Conclusion
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In contrast to the germination usually done in petri dishes, the plants are able to orientate their roots vertically through the gauze material into the distilled water below (Fig. 2b). This method is easy to handle, needs no laborious preparation, and is suitable for all higher plants, whose seeds float on water. The necessary equipment is available anywhere and is of low expense. It therefore allows disposal of the materials after use. This is the most convincing advantage of this method, because this helps to save time. Hydroculture needs in particular clean handling to prevent sepsis of the roots. The method of Brunner et al. (1996) instead needs time for tedious preparing of the plant carriers and additional time to clean them before reuse. Our method instead allows the handling of a large set of replicates, which is of essential statistical use in the testing of biota. About 60 beakers per hour can be loaded for testing. The gauze is a perfect carrier for plants, for it allows the plants to grow without hindrance and its flexibility helps to get the plant out of the carrier easily for weighing. The Styropor pellets do not disturb the germination process and are washed out of the roots after germination without any further problem, so that the pellets do not play any role in absorption of test solution elements.
Nonetheless, hydroculture plant tests are not the ideal method for ecotoxicological testing. The hydroculture system has no buffer and is therefore very susceptible to allelopathic effects and sepsis, which then affect all plants in the same beaker. Even though higher plants are the equivalent species for testing terrestrial ecotoxicity, higher plant tests generally encounter a huge variance (30–100%) (Moewus, 1949). Therefore, statistical significance is not easily achieved.
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REFERENCES
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- Brunner, I., J. Luster, M. Ochs, and P. Blaser. 1996. Phytotoxic effects of the higher molecular weight fraction of an aqueous leaf litter extract on barley root development. Plant Soil 178:83–93.
- Fialová, S. 1969. Influence of sodium humate and nutritive conditions on the content of nucleic acids, particularly on the ribosomal ribonucleic acid in wheat roots. Biol. Plant. 11:8–22.
- Füll, C., S. Jung, and C. Schulte. 2000. Plant protection products: Assessing the risk for terrestrial plants. Chemosphere 41:625–629.[Medline]
- Günther, P., W. Pestemer, A. Rahman, and H. Nordmeyer. 1993. A bioassay technique to study the leaching behavior of sulfonylurea herbicides in different soils. Weed Res. 33:177–185.
- Loffredo, E., N. Senesi, and V. D'Orazio. 1997. Effects of humic acids and herbicides, and their combinations on the root growth of tomato seedlings in hydroponics. Z. Pflanzenernähr. Bodenkd. 160:455–461.
- Lüssem, H., and A. Rahman. 1980. Wurzellängentest mit Gartenkresse-ein einfacher ökotoxikologischer Test. Vom Wasser 54:29-35.
- Moewus, F. 1949. Der Kressewurzeltest – ein neuer quantitativer Wuchsstofftest. Biologisches Zentralblatt 68:118–139.
- Senesi, N., and E. Loffredo. 1994. Influence of soil humic substances and herbicides on the growth of pea (Pisum sativum L.) in nutrient solution. J. Plant Nutr. 17:493–500.
- mídová, M. 1960. The influence of humus acid on the respiration of plant roots. Biol. Plant. 2:152–164.
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