Abstract
To better understand the behavior of the plants towards xenobiotics, two species of bryophytes (<i>Orthotrichum affine</i> and <i>Scleropodium purum</i>), bioindicators of the region of Souk Ahras (Algeria) which have properties completely different (classification, reproductive cycle...) are treated under hydroponic conditions by 125, 250, 500, 1000 and 1500 mg / L of Sencorate herbicide (Metribuzin) for 3, 7, 14 and 21 days. A measure of some physiological, biochemical and enzymatic parameters characteristic of oxidative stress have allowed us to evaluate not only the effect of Sencorate herbicide but also the behavior of the two species with respect to pollution. Statistical analysis of the results showed significant differences between the treated and control samples for the majority of parameters studied, with lower levels of chlorophyll pigments (<i>a, b, a+b</i>) accompanied by increased levels of proline, total protein and soluble carbohydrates. Depletion of GSH at the beginning of treatment, accompanied by an increase in Malondialdehyde MDA levels were observed with low activity of the enzyme biomarkers Catalase and Ascorbat peroxydase (CAT and APX), which reflects the high tolerance of these species to pollutants.
Highlights
Since a few decades, the growth and diversity of human activities were accompanied by the release into the environment of quantities of xenobiotic harmful to human health [1]
The results indicate that chlorophyll pigments, metabolites and enzymatic biomarkers show varying patterns depending on the exposure time in both species
During the treatment of 3 and 7 days, significant increases in levels of proline and total protein were observed in both species (Figure 3 a and b ), especially with the highest herbicide dose (1500 mg / L ) (38, 47 μg / mg of FM was recorded for proline of the species O. affine), a decrease was noted from the 14th day, in which the application of high concentration of herbicide registering the weakest levels of these two metabolites, except the rate of total protein its increase in S. purum at the 21th day (Figure 3a)
Summary
The growth and diversity of human activities were accompanied by the release into the environment of quantities of xenobiotic harmful to human health [1]. The analysis of the mechanisms of response to oxidative stress or oxidative stress - xenobiotic interactions may provide a better understanding of the processes of response to xenobiotics [4]. The exposure of photosynthetic organisms to certain environmental pollutants causes an overproduction of reactive oxygen species (ROS), causing oxidative stress which can lead to death [8]. Many organic xenobiotics, such as herbicides, can cause an overproduction of ROS. This accumulation may be due to an inhibition of electron transport related to photosynthesis process, and to an inhibition of the photosystem activity [9]
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