Evaluation of photosynthetic oxygen production, pigment pattern, glutathione content and detoxication enzymes activity in the aquatic macrophyte Ceratophyllum demersum exposed to cypermethrin

Cypermethrin is a widespread pyrethroid that can be very toxic for certain taxa, but there is a lack of information concerning its effects within the plant kingdom. Exposures to different concentrations as well as at different times were carried out in the aquatic macrophyte Ceratophyllum denersum in order to evaluate effects on photosynthetic oxygen production, chlorophyll a and b, total glutathione content and detoxication enzymes. Activity of guaiacol peroxidase (POD), glutathione reductase (GR), microsomal and cytosolic glutathione S-transferases (M- and cGST, respectively, from phase II of metabolism) were measured. No significant effects on photosynthetic oxygen production or on chlorophyll content were found. On the other hand, there was and noticeable activation of POD at the higher concentrations tested and the time-response curve for 50 µg/L showed that its activation was significant until day 3 in comparison to the controls. At 0.5-5 µg L-1 of cypermethrin the activity of cGST and GR enzymes as well as the total GSH content were not significantly different from the controls. At 50 µg L-1 mGST was significantly activated but the activity of cGST and total GSH content were not different from the controls. GR was not activated at any concentration or time tested. Although some detoxication responses at day 3 of exposure in the physiological system of C. demersum when exposed to a high dose of cypermethrin seemed to happen, it appears that environmentally relevant concentrations of this insecticide do not result in any significant damage to this aquatic macrophyte.