John T. Barber

Detoxification of phenol by the aquatic angiosperm, Lemna gibba

Lemna gibba was used to study the toxicity and metabolism of phenol. The toxicities of phenol and its major metabolite were described in terms of the effect of increasing concentrations on the vegetative reproduction of duckweed over a 7-day growth period. The respective EC10 and EC50s were 0.08 & 0.54 mM for phenol and 0.15 & l.10 mM for the major plant-produced metabolite which was subsequently isolated from the plants growth medium. After purification, the metabolite was identified, by 400 MHz NMR and chemical ionization MS. The structural identity was confirmed by comparison with authentic phenyl-β-D-glucopyranoside that had been acetylated.

The physiological consequences of ethylene glycol-induced changes in the frond structure of Lemna gibba

Abstract Ethylene glycol is the major component of many antifreeze/coolant and deicant formulations. Its use as an aircraft/runway deicant ensures that it is a major but intermittent pollutant of surface waters in the vicinity of those airports where it is used. Other uses, such as in automobile radiators or as a hydraulic fluid, result in smaller but more continuous and widespread releases. However, ethylene glycol is usually thought of as being relatively benign and therefore its fate and effects in higher plants have received little attention. Using axenic cultures of the aquatic angiosperm, Lemna gibba (duckweed), it has been shown that while ethylene glycol is not metabolized and is relatively non-toxic as far as vegetative reproduction in duckweed is concerned (EC10 and EC50 were 5740 and 10 920 ppm, respectively), it does have dramatic effects upon the structure of young fronds during their early growth and development. The result of the changes in frond structure is to increase the uptake of water and solutes from the surrounding environment. It is suggested that an increase in the uptake of a nutrient can lead to enhanced growth whereas an increase in the uptake of a toxicant can lead to the potentiation of its toxicity. In either case, the ecological consequences could be profound.

The attraction of larvae of Culex pipiens quinquefasciatus Say to ribonucleic acid and nucleotides.

Abstract The positive chemotaxis of larvae of Culex pipiens quinquefasciatus in response to RNA or its degradation products has been demonstrated. It has further been shown that larvae are specifically attracted to certain nucleoside monophosphates. The observations are related to the known dietary requirements of mosquito larvae.