In this paper the main object is to study the recovery of Lemna minor after exposure to uranium, cadmium or gamma radiation. Exposure to uranium or cadmium results in a concentration dependent inhibition of Lemna growth. The photosynthetic activity and concentrations of pigments decline as well. After a regrowth period the plants show some recovery, there is less growth inhibition for the surface area of the plants. This means that new developed leafs are bigger. For the photosynthetic activity as well as the pigment concentrations the recovery is clearly visible for both metals. Only the plants contaminated with a uranium concentration of 50 µM have values lower than the control. After exposure to gamma radiation the results show a growth inhibition with an increased dose of radiation. The photosynthesis, however, seems stimulated by the radiation exposure. The photosynthetic activity shows an increase in the plants that were exposed to the lowest dose rate (25 mGy/u). The pigment concentrations didn’t increase or decline for chlorophyll a and chlorophyll b, the concentration carotenoids increased from a dose rate of 150 mGy/u. After the regrowth it seems that the plants that were exposed to the highest dose rate of gamma radiation (450 mGy/u) are nearly dead. The growth inhibition increased drastically and the photosynthesis declined strongly. The plants exposed to the other doses of gamma radiation have a small decline in photosynthesis and coincide again with the values of the control group. Lemna minor plants clearly react during the exposure and during the regrowth after being exposed to the contaminants. The nature of reaction and the extent of the recovery depends on the contaminant and their concentration. The data of this study confirm the need to take time of exposure (or recovery) into account when trying to estimate the impact of stressors on organisms.
|Published - 30 Jun 2015