Studies on the Flowering Mechanism in <i>Lemna</i>

Maeng, Jueson; Khudairi, A. K.

doi:10.1111/j.1399-3054.1973.tb01187.x

Cited by 53 publications

(26 citation statements)

References 7 publications

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“…The only exception, terbuthylazine (log K ow : 3.2)25 showed EC 50 values comparable with those obtained on the basis of measured terbuthylazine concentrations 26. The L. minor plants were collected in Copenhagen in 1999, surface sterilised with hypochlorite and the resulting sterile clone was kept in Ehrlenmeyer flasks in ‘K’‐medium,27 pH 5, at 24 °C and a continuous photon flux density of 85–120 µmol m −2 s −1 photosynthetic active radiation (PAR). The flasks and medium were sealed with cotton wool and autoclaved before the weekly transfer of plants to new media.…”

Section: Methodssupporting

confidence: 59%

Combination effects of herbicides on plants and algae: do species and test systems matter?

Cedergreen¹,

Kudsk²,

Mathiassen³

et al. 2007

Pest Management Science

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Risk assessment of herbicides towards non-target plants in Europe is currently based solely on tests on algae and floating aquatic plants of Lemna sp. Effects on terrestrial non-target species is not systematically addressed. The purpose of the present study was to compare combination effects of herbicide mixtures across aquatic and terrestrial test systems, and to test whether results obtained in the traditional aquatic test systems can be extrapolated to the terrestrial environment. This was done by evaluating ten binary mixtures of nine herbicides representing the seven most commonly used molecular target sites for controlling broadleaved weeds. Data were evaluated statistically in relation to the concentration addition model, and for selected concentrations to the independent action model. The mixtures were tested on the terrestrial species Tripleurospermum inodorum (L.) Schultz-Bip. (Scentless Mayweed) and Stellaria media (L.) Vill. (Common Chickweed), and on the aquatic species Lemna minor L. (Lesser duckweed) and the alga Pseudokirchneriella subcapitata (Korschikov) Hindak. For the two mixtures of herbicides with the same molecular site of action, the joint effect was additive. For the eight mixtures of herbicides with different sites of action, two of the mixtures were consistently antagonistic across species, while for the remaining six mixtures the joint effect depended on the species tested. This dependence was, however, not systematic, in the sense that none of the species or test systems (terrestrial versus aquatic) had a significantly higher probability of showing synergistic or antagonistic joint effects than others. Synergistic interactions were not observed, but approximately 70% of the mixtures of herbicides with different sites of action showed significant antagonism. Hence, the concentration addition model can be used to estimate worst-case effects of mixtures of herbicides on both terrestrial and aquatic species. Comparing the sensitivity of the species to a 10% spray drift event showed that the terrestrial species were more vulnerable to all herbicides compared with the aquatic species, emphasising the importance of including terrestrial non-target plants in herbicide risk assessment.

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Section: Methodssupporting

confidence: 59%

Combination effects of herbicides on plants and algae: do species and test systems matter?

Cedergreen¹,

Kudsk²,

Mathiassen³

et al. 2007

Pest Management Science

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“…Concentrations were the same as those used for the algae test and were chosen on the basis of preliminary tests. Artemisinin was dissolved in acetone, and 250 μl of this solution were added to 0.5 L of growth medium prepared according to the method described by Maeng and Khudairi [33]. The solution was magnetically stirred and acetone allowed to evaporate for 3 h. The L. minor plants (type UTCC 490) were purchased from Judy Acreman, University of Toronto Culture Collection of Algae and Cyanobacteria (Toronto, ON, Canada), and were kept aseptically in Erlenmeyer flasks in growth medium at 24°C, pH 5, and a continuous photon flux density of 85 to 120 μmol/m 2 /s of PAR.…”

Section: Methodsmentioning

confidence: 99%

Degradation and ecotoxicity of the biomedical drug artemisinin in soil

Jessing

Cedergreen

Jensen

et al. 2009

Enviro Toxic and Chemistry

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The plant Artemisia annua L. is cropped in many countries for production of the antimalarial drug artemisinin. Artemisinin is phytotoxic and has insecticidal activity. Large-scale cultivation of A. annua may cause transfer of artemisinin to soil and, hence, may affect both soil organisms and the aquatic environment if the compound is leachable. In the present study, a new method for extraction of artemisinin from soil was developed, and field concentrations and degradation kinetics of artemisinin in sandy and loamy soils were measured. The soil concentrations in a Danish A. annua field were up to 11.7 mg/kg. The degradation kinetics could be modeled as the sum of two first-order reactions, a fast initial degradation followed by a reaction that was 11- to 25-fold slower. It took at least 35 d before artemisinin could not be detected (<0.36 mg/kg) at 20 degrees C, classifying artemisinin as being relatively persistent in the environment. Combined with its water solubility of 49.7 +/- 3.7 mg/L, this makes it potentially leachable. In soil, artemisinin repelled the earthworm (Eisenia fetida; the 10 and 50% effect concentrations [EC10s and EC50s, respectively] were 5.24 +/- 2.64 and 21.57 +/- 4.73 mg/kg, respectively) and inhibited growth of lettuce (Lactuca sativa L.; EC50, 2.48 mg/kg). Springtails (Folsomia candida) were not affected in the tested concentration range of 1 to 100 mg/kg. Artemisinin had toxicity to the freshwater algae (Pseudokirchneriella subcapitata; EC50, 0.24 +/- 0.01 mg/L) and duckweed (Lemna minor; EC50, 0.19 +/- 0.03 mg/L) similar to that of the commercial herbicide atrazine. Based on the presented data, the risks of adverse environmental effects because of cultivation of A. annua are high and comparable to those when using commercial pesticides.

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“…Lemna minor was collected from a local pond in Copenhagen, Denmark in 1999. The plants were surface sterilized according to Landolt and Kandeler16 and the clone has since then been kept in Ehrlenmeyer flasks in ‘K’‐medium,17 pH 5, at 24 °C and a continuous photon flux density of 85–120 µmol m −2 s −1 (photosynthetically active range; PAR). The flasks and medium are sealed with cotton wool and autoclaved before the weekly transfer of plants to new media.…”

Section: Methodsmentioning

confidence: 99%

The toxicity of herbicides to non‐target aquatic plants and algae: assessment of predictive factors and hazard

Cedergreen¹,

Streibig²

2005

Pest Management Science

151

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Widely used herbicides sometimes inadvertently contaminate surface waters. In this study we evaluate the toxicity of herbicides to aquatic plants and algae and relate it to environmental herbicide concentrations and exposure scenarios, herbicide formulation and mode of action. This was done experimentally for ten herbicides, using the aquatic macrophyte Lemna minor L. and the green alga Pseudokirchneriella subcapitata (Korshikov) Hindak, supplemented with a database study comprising algae toxicity data for 146 herbicides. The laboratory study showed that herbicide formulations in general did not enhance herbicide efficacy in the aquatic environment. The Roundup formulation of glyphosate proved to be the only exception, decreasing the EC(50) of the technical product for both L. minor and P. subcapitata approximately fourfold. Comparison of the sensitivity of L. minor and P. subcapitata revealed up to 1000-fold higher sensitivity of L. minor for the herbicides categorized as weak acids (pK(a) < 5), emphasizing the importance of higher plants in hazard assessment. Database analyses showed that no herbicide group, categorized by site of action, was significantly more toxic than another. Synthetic auxins were the exception as they are virtually non-toxic to unicellular algae. There was no strong correlation between toxicity to algae and K(ow) of the herbicides, not even within groups having the same site of action. Evaluating all data, few herbicides were toxic at concentrations below 1 microg l(-1), which is the 99.9th percentile of the herbicide concentrations measured in the Danish surveillance programme. Joint action of several herbicides cannot however be excluded.

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Studies on the Flowering Mechanism in Lemna

Cited by 53 publications

References 7 publications

Combination effects of herbicides on plants and algae: do species and test systems matter?

Combination effects of herbicides on plants and algae: do species and test systems matter?

Degradation and ecotoxicity of the biomedical drug artemisinin in soil

The toxicity of herbicides to non‐target aquatic plants and algae: assessment of predictive factors and hazard

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