Morphological effect of dichloromethane on alfalfa (Medicago sativa) cultivated in soil amended with fertilizer manures

In this work, we investigated the morphological effect of dichloromethane (DCM) on alfalfa (Medicago sativa) plant. We studied in vitro the influence of its concentration on alfalfa germination. The plants were placed in pots for 15 weeks, and exposed to increasing concentrations of DCM (50 µg L−1 and 84 mg L−1). In addition, we examined the effect of two manures (cow and sheep), which were applied to a contaminated soil, on alfalfa plant growth. The effect of the presence of dichloromethane is obvious even in plant–soil manure system. In fact, in the event of contamination, the soil–cow manure mixture represents the best setting medium for the Alfalfa plant compared to other environments, regardless of the contamination level. Indeed, the presence of two types of manure does not allow the suppression of the inhibitory effect of dichloromethane on the mass of the dry matter of the aerial part which is 18.38% for the cow manure-amended soil and 13.96% for the sheep manure-amended soil

Effect of treated wastewater irrigation on physiological and agronomic properties of beans Vicia faba

The current study investigated the effect of two doses (50%, and 100 %) of treated wastewater (TWW)on biometric and physiologic parameters of Vicia faba beansafter 40 days of exposure. Our data showed a decrease in shoots and roots length and weight in plants amended with TWW. Moreover, a significant decrease in Chlorophyll ‘a\u27, ‘b\u27 and carotene content was observedin plants irrigated with 100% of TWW. These findings provided new insights on TWW reuse which can cause different types of stress as it may affect the development of cultivated crops

Effect of reduced tillage under various mulch types on soil fertility and yield of an organic pepper crop

The effects of mulching on soil characteristics and plant development for pepper crops conducted in organic farming were studied in the Sahel coast of Tunisia. The types of mulching used for tests are straw mulching, compost mulching, and plastic mulching which were compared with bare soil without mulching (control). The soil characteristics under these different mulching systems were evaluated by soil physical and biological parameters such as penetration resistance at 0-60 cm layer, microbial biomass, organic matter, and water content at 0-20 cm layer. Measurements were performed every week for 50 days. The obtained results showed that compost mulching led to a better growth rate and improved the structural and water state of cultivated soil by decreasing its resistance to penetration and increasing its organic matter content. It can be concluded that the "Beldi" organic pepper crop under conservation tillage and compost mulching has presented the best combination thus leading to motivating results such as the positive effects of soil physical properties and microbial biomass on the final crop yield

Impact of heavy metal contamination on oxidative stress of Eisenia andrei and bacterial community structure in Tunisian mine soil

International audienceThe aims of this work were firstly to study the effect of heavy metal-polluted soils from Tunisian mine on earth-worm biochemical biomarkers and on bacterial communities and therefore to analyze the interaction between earth worms and bacterial communities in these contaminated soils. For this purpose, we had introduced earthworm Eisenia andrei in six soils: one from mine spoils and five from agricultural soils, establishing a gradient of contamination. The response of worms to the presence of heavy metal was analyzed at the biochemical and transcriptional levels. In a second time, the impact of worm on bacterial community structure was investigated using automated ribosomal intergenic spacer analysis (ARISA) fingerprinting. An impact of heavy metal-contaminated soils on the oxidative status of E. andrei was observed, but this effect was dependent of the level of heavy metal contamination. Moreover, our results demonstrate that the introduction of earthworms E. andrei has an impact on bacterial community; however, the major change was observed in the less contaminated site. Furthermore, a significant correlation between earthworm oxidative status biomarkers and bacterial community structure was observed, mainly in the mine spoils. Therefore, we contribute to a better understanding of the relationships between epigenic earthworms and bacterial communities in heavy metal-contaminated soils

Effects of cadmium and copper on pollen germination and fruit set in pea (Pisum sativum L.)

In this work, pea (Pisum sativum) plants exposed to increasing cadmium and copper concentrations were tested for heavy metals accumulation in flowers and for '. in vivo' pollen germination. Based on the Cd and Cu accumulation amounts in the flowers, an evaluation of the same metals effects on '. in vitro' pollen germination was achieved. Moreover, the effects of both metals on fruits number and weight and on seed set and yield at individual plant level were examined. While cadmium concentrations did not affect '. in vivo' pollen germination, only higher copper concentrations rendered a significant reduction. This is in contrast with the clear negative effect on pollen germination in vitro and might be explained by the different dynamic and bioavailability of both metals. A clear effect of Cd and Cu was observed on two important yield components ie, fruit weight and seed set. Although results obtained herein cannot give a clear cut relationship between the effect of Ca and Cu on reproductive development and its consequences on yields, they represent emerging results on the potential consequences of metals contamination on reproductive development in plants.The work was partially supported by funds from the Tunisian Ministry of Higher Education, Scientific Research and Technology, and by the Research Unit “Biochemistry and Ecotoxicology”. Financial support for this work was also provided by the Spanish project grants CICYT AGL2006-13529-C02-00/AGR and by the cooperation grant AECI A/4868/06.Peer Reviewe

Characterisation of lead-induced stress molecular biomarkers in Medicago sativa plants

In this study, we investigated physiological changes and transcriptional responses in four-week-old hydroponically grown Medicago sativa seedlings exposed to (PbNO3)2 (0, 10 and 100 mM) for 2 and 7 days. Fresh weight and length were reduced in both shoots and roots after 7 days exposure. Lead accumulation was time and dose-dependent with stronger phytotoxic effects in roots than in shoots, with a relatively low amount of Pb translocated from roots to shoots. Lipid peroxidation augmented remarkably, suggesting the onset of oxidative damages, with increased glutathione reductase (GR), ascorbate peroxidase (APX) and superoxide dismutase (SOD) activities. This result was accompanied by a remarkable up-regulation of APX and SOD genes. In roots, the increase of SOD transcripts was concomitant to an enhanced SOD enzymatic activity in all Pb treatments. However, the 30-fold upregulation occurred with a remarkable APX activity inhibition, which suggests that there might be posttranscriptional modifications able to regulate root APX. Root glutathione (GSH) and omoglutathione (hGSH) concentrations decreased in a dose dependent manner, while we could not detect the accumulation of phytochelatins (PC), albeit the related gene was up-regulated. The lack of PCs synthesis suggests a post-translational regulation of its enzymatic activity. Heat shock proteins (HSP70 and HSP17.7) were increased in alfalfa shoots, implying the triggering of cellular protection mechanism to cope with lead phytotoxicity. It is concluded that alfalfa plants mitigate the oxidative damage through induction of antioxidant enzymes, and the expression of chaperone proteins to alleviate Pb toxicity; metabolic changes that could be exploited as Pb-stress bioindicators

Biomarker responses of Eisenia andrei to a polymetallic gradient near a lead mining site in North Tunisia

Eisenia andrei earthworms were exposed for 7 and 14 days to six samples of soil taken from around an abandoned lead (Pb) mine and characterized by different levels of metal contamination (S6-S1, this latter being the most contaminated soil). The organisms were analyzed for metal bioaccumulation and for biological parameters as biomarkers of stress (lysosomal membrane stability; lipofuscin lysosomal content; lysosomal/cytoplasmic volume ratio) and genotoxicity (Micronucleus frequency). Chemical analysis showed the loads of Pb, Cd, Zn, and Cu in the worms following exposure. Among the stress biomarkers, lysosomal membrane stability was significantly affected in the coelomocytes of the earthworms exposed already 7 days to different contaminated soils. Organisms exposed for 14 days to S1 showed in the cells of the chloragogenous tissue, a particularly relevant increase in lipofuscin, a biomarker of oxidative stress, and an increase in the lysosome/cytoplasm volume ratio, indicating stressful condition at the tissue level. Moreover, in the same conditions, a decrease in total body weight was observed. At the longer exposure time, the coelomocytes of worms exposed to S1, S2, and S3 (soils with higher metal concentrations) showed a significant increase in micronuclei (MNi) frequency. Expressions of the P21 and topoisomerase genes, which are involved in DNA repair, showed significant up-regulation in the cells of worms exposed to S1, S2, S3, S4 and to a less extend S6. This may indicate that the worms were only able to successfully reduce the level of DNA damage in S4 and S5 if considering MN frequency data. The biomarker data was integrated by the Earthworm Expert System, allowing an objective interpretation of the complex biological data and clearly defining the areas in which the presence of chemicals is toxic for the edaphic organisms

Effect of reduced tillage under various mulch types on soil fertility and yield of an organic pepper crop

The effects of mulching on soil characteristics and plant development for pepper crops conducted in organic farming were studied in the Sahel coast of Tunisia. The types of mulching used for tests are straw mulching, compost mulching, and plastic mulching which were compared with bare soil without mulching (control). The soil characteristics under these different mulching systems were evaluated by soil physical and biological parameters such as penetration resistance at 0-60 cm layer, microbial biomass, organic matter, and water content at 0-20 cm layer. Measurements were performed every week for 50 days. The obtained results showed that compost mulching led to a better growth rate and improved the structural and water state of cultivated soil by decreasing its resistance to penetration and increasing its organic matter content. It can be concluded that the "Beldi" organic pepper crop under conservation tillage and compost mulching has presented the best combination thus leading to motivating results such as the positive effects of soil physical properties and microbial biomass on the final crop yield