Duckweed, Lemna

Certain emergent aquatic plants, especially hydrilla (Hydrilla verticillata) and duckweed (Lemna obscura), removed 97 to 98% of all soluble lead from solution in the vicinity of a lead battery site in Tampa, Florida, suggesting that phytoremediation may be feasible as the basis of a lead removal technology (Gallardo et al. 1999). 

Duckweed, Lemna media 30 Reduced growth in 10 days 31... 

Fujisawa T, Kurosawa M, Katagi T (2006) Uptake and transformation of pesticide metabolites by duckweed (Lemna gibba). J Agric Food Chem 54 6286-6293... 

Valencia-Islas NA, Paul RN, Shier WT, Mata R, Abbas HK, Phytotoxicity and ultrastructural effects of gymnopusin from the orchid Maxillaria densa on duckweed Lemna pausicostatd) frond and root tissues, Phytochemistry 61 l4l—148, 2002. 

Lesser duckweed, Lemna minor Submerged weeds 4 species 3 species... 

Frick, H. 1985. Boron tolerance and accumulation in the duckweed, Lemna minor. Jour. Plant Nutr. 8 1123-1129. 

Thomas, J. D., and P. Eaton. 1996. The accumulation of amino-acids and humic substances in media conditioned by axenic and non-axenic duckweed (Lemna minor L.) and their possible ecological significance. Hydrobiologia 333 121-128. 

Bengtsson, B.-E., Bongo, J.P. and Eklund, B. (1999) Assessment of duckweed Lemna aequinoctialis as a toxicological bioassay for tropical environments in developing countries, Ambio 28 (2), 152-155. 

Jenner, H.A. and Janssen-Mommen, J.P.M. (1989) Phytomonitoring of pulverized fuel ash leachates by the duckweed Lemna minor, in M. Munawar, G. Dixon, C.I. Mayfield, T. Reynoldson and M.H. Sadar (eds.), Environmental Bioassay Techniques and their Application Proceedings of the 1st International Conference held in Lancaster, England, 11-14 July 1988, Kluwer Academic Publishers, Dordrecht, Netherlands, pp. 361-366. 

There is virtually no literature describing bioconcentration of organic compounds by wild aquatic macrophytes in spite of the facts that these plants are often the major primary producers in shallow inland waters, and are essential habitat components for both aquatic and terrestrial animals. Lockhart et al. (14) provided a regression equation describing uptake curves for a variety of organic compounds by duckweed (Lemna minor) cultures in laboratory exposures. Predictions from the regression equation agreed quite well with field observations on bioconcentration of permethrin in outdoor ponds (15). 

The intent of this study was to derive rate constants describing uptake and depuration of some forest pesticides using fish (rainbow trout, Salmo gairdneri) and an aquatic macrophyte (duckweed, Lemna minor) in laboratory tests. Since some formulations of forest pesticides also contain solvents of petroleum distillates, experiments were also carried out with a hydrocarbon, fluorene, which is a component of fuel oil (16). 

Algae—diatoms (Skelotonema costatum, Phaeodactylum tricomutum) Duckweed (Lemna minor)... 

Corbet et al. (1983) reported that a rooted plant species (Potemagetonpectimatus) and a surface-dwelling duckweed (Lemna sp.) accumulated concentrations of 1,3,6,8-TCDD of 280 and 105 ng/g (dry weight), respectively, following exposure to water containing 1,000 ng/L (ppt). The maximum concentrations were observed 8 days post-application and represented 6% of the total TCDD applied. These results are similar to those reported by Tsushimoto et al. (1982) in an outdoor pond study, in which a maximum bioaccumulation of 2,3,7,8-TCDD in the pond weeds Elodea nuttali and Ceratophyllon demersum equivalent to a BCF of 130 occurred after 5 days of exposure. In both studies, the tissue concentrations reached equilibrium in approximately 20 days and remained constant until the end of the experiment (approximately 58 and 170 days, respectively). These experimental data indicate that CDDs can accumulation in aquatic plant species through waterborne exposure. 

Leaf discs have commonly been used for bioassays to determine if herbicides inhibit photosynthesis (Table 16.2). The simplest leaf-disc bioassay uses small discs cut from fully expanded cucumber or pumpkin cotyledons, floated in the light on a phosphate buffered medium containing suspected photosynthesis inhibitors.115 Qualitatively, if photosynthesis is inhibited, the leaf disc sinks. There are several variations of this method that can provide quantitative data. Evolution of O2 in the test solution can be measured with an oxygen electrode, CO2 induced pH changes colorimetrically determined with bromothymol-blue, or electrolyte leakage monitored with a conductivity meter. Leaf strips, algae, isolated chloroplasts, and duckweed (Lemna minor) have been used as test subjects. Although the bioassays presented in Table 16.2 are fairly easy to perform, few allelochemicals have been tested as possible inhibitors of photosynthesis. Many... 

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