7 Effects of Pharmaceuticals in Terrestrial Organisms
7.1 Pharmaceutical-Induced Effects in Plants
Once in the environment, pharmaceuticals can maintain their biological potency
which has the potential to elicit effects in plants following their uptake and accumulation. Some of the earliest research documenting effects on plants observed
phytotoxicity in response to antibiotic exposure, with studies dating back to as
early as the 1980s [117].
For example, the antibiotic sulphadimethoxine was found to suppress normal
post-germinative development and growth of barley (Hordeum distichum L.) roots
and leaves growing both on synthetic medium and on soils with different organic
content (0–10%) [118]. At harvest, on day 45 of the soil test, barley wet weight in
sulphadimethoxine exposures was reduced (pooled treated: 571.10 mg) in comparison to the controls (pooled control: 772.43 mg). Effects were observed at exposure
concentration of 300 mg/L and were dependent on the bioaccumulation rate.
Sulphadimethoxine dissolved in a nutrient solution was also found to induce a
45% decrease in root growth of barley seedlings (Hordeum vulgare L.) at a concentration of 40 μM [119]. These results were in agreement with previous experimental
data on millet (Panicum miliaceum), pea (Pisum sativum) and maize (Zea mays)
demonstrating a reduction in root, stalk and leaf growth in response to
sulphadimethoxine exposure [65].
In a later study, Migliore et al. [120] evaluated the phytotoxicity of enrofloxacin
(50, 100 and 5,000 ug/L) on crop plants Cucumis sativus, Lactuca sativa, Phaseolus
vulgaris and Raphanus sativus. Concentrations between 50 and 5,000 μg/L induced
both toxic effects and hormesis in plants, by significantly modifying both length of
primary root, hypocotyl and cotyledons and the number/length of leaves.
Enrofloxacin altered all the examined plant organs; however, interestingly, this did
not occur in a linear dose-dependent manner: 50 μg/L exposure increased the length/
number of Cucumis sativus leaves, 5,000 μg/L exposure decreased in comparison to
control, whilst at 100 μg/L, an intermediate response was seen. A similar biphasic
dose response was also observed in Raphanus sativus and Lactuca sativa, whereby a
slight increase in leaf length was measured at lower concentrations.
Both shoot and root biomass of alfalfa (Medicago sativa L.) decreased sharply
with increasing concentrations of another antibiotic, oxytetracycline, in a growth
solution [37]. Whilst oxytetracycline had no effect on alfalfa shoot biomass at
0.002 mM concentrations, the root biomass decreased significantly ( p < 0.05)
when the OTC concentration was above 0.002 mM. In addition, oxytetracycline
decreased shoot and root fresh weight by a maximum of 61% and 85%, respectively,
with the shoot/root ratio increasing significantly at lower exposure concentrations,
which suggested that the roots are more sensitive to oxytetracycline than shoots.
Similar results were also found by Hillis et al. [121] who observed that roots
(carrots) were more sensitive to a suite of ten antibiotics, often by an order of
magnitude or more, in comparison to shoots such as lettuce and alfalfa. The response
Uptake and Effects of Pharmaceuticals in the Soil-Plant-Earthworm System
205
7.1 Pharmaceutical-Induced Effects in Plants
Once in the environment, pharmaceuticals can maintain their biological potency
which has the potential to elicit effects in plants following their uptake and accumulation. Some of the earliest research documenting effects on plants observed
phytotoxicity in response to antibiotic exposure, with studies dating back to as
early as the 1980s [117].
For example, the antibiotic sulphadimethoxine was found to suppress normal
post-germinative development and growth of barley (Hordeum distichum L.) roots
and leaves growing both on synthetic medium and on soils with different organic
content (0–10%) [118]. At harvest, on day 45 of the soil test, barley wet weight in
sulphadimethoxine exposures was reduced (pooled treated: 571.10 mg) in comparison to the controls (pooled control: 772.43 mg). Effects were observed at exposure
concentration of 300 mg/L and were dependent on the bioaccumulation rate.
Sulphadimethoxine dissolved in a nutrient solution was also found to induce a
45% decrease in root growth of barley seedlings (Hordeum vulgare L.) at a concentration of 40 μM [119]. These results were in agreement with previous experimental
data on millet (Panicum miliaceum), pea (Pisum sativum) and maize (Zea mays)
demonstrating a reduction in root, stalk and leaf growth in response to
sulphadimethoxine exposure [65].
In a later study, Migliore et al. [120] evaluated the phytotoxicity of enrofloxacin
(50, 100 and 5,000 ug/L) on crop plants Cucumis sativus, Lactuca sativa, Phaseolus
vulgaris and Raphanus sativus. Concentrations between 50 and 5,000 μg/L induced
both toxic effects and hormesis in plants, by significantly modifying both length of
primary root, hypocotyl and cotyledons and the number/length of leaves.
Enrofloxacin altered all the examined plant organs; however, interestingly, this did
not occur in a linear dose-dependent manner: 50 μg/L exposure increased the length/
number of Cucumis sativus leaves, 5,000 μg/L exposure decreased in comparison to
control, whilst at 100 μg/L, an intermediate response was seen. A similar biphasic
dose response was also observed in Raphanus sativus and Lactuca sativa, whereby a
slight increase in leaf length was measured at lower concentrations.
Both shoot and root biomass of alfalfa (Medicago sativa L.) decreased sharply
with increasing concentrations of another antibiotic, oxytetracycline, in a growth
solution [37]. Whilst oxytetracycline had no effect on alfalfa shoot biomass at
0.002 mM concentrations, the root biomass decreased significantly ( p < 0.05)
when the OTC concentration was above 0.002 mM. In addition, oxytetracycline
decreased shoot and root fresh weight by a maximum of 61% and 85%, respectively,
with the shoot/root ratio increasing significantly at lower exposure concentrations,
which suggested that the roots are more sensitive to oxytetracycline than shoots.
Similar results were also found by Hillis et al. [121] who observed that roots
(carrots) were more sensitive to a suite of ten antibiotics, often by an order of
magnitude or more, in comparison to shoots such as lettuce and alfalfa. The response
Uptake and Effects of Pharmaceuticals in the Soil-Plant-Earthworm System
205