Effect of different levels of nitrogen fertilizer on morphological and physiological parameters and nitrates accumulation of lettuce cultivars (Lactuca sativa L.)

The effect of nitrogen fertilizer level on growth and nitrate accumulation was studied in six lettuce cultivars (Lactuca sativa L.): ‘Batavia rouge’, ‘Vitalia’, ‘Great Laks’, ‘Type Beurre’, ‘Romaine’ and ‘Romaine LO3’. Three nitrogen levels: 0, 120 and 240 Kg.ha-1 was applied. During plant growth, agronomical parameters (root weight, fresh and dry matter, head diameter) and physiological parameters (nitrate concentration, chlorophyll fluorescence and sugar content) were evaluated. Results showed significant differences between cultivars and nitrogen treatment for the most agronomical and physiological parameters. The nitrogen treatment affects head weight and nitrate concentration in all cultivars; the cvs ‘Great Laks’ and ‘Type beurre’ accumulated respectively the less and high nitrate concentration. The highest nitrate concentration was recorded in external leaves whereas the lowest concentration was recorded in the central leaves for all cultivars. Furthermore, nitrate distribution and chlorophyll fluorescence on the leaves are closely related. This study revealed also correlation between root nitrate concentration, chlorophyll fluorescence and sugar content for all cultivars. This correlation depended on nitrogen fertilization level and the cultivar used

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 Aloe Vera wastes on physico-chemical properties and microbiological activity in soils

The aim of the present study was to explore the potential for using aloe vera wastes as amendment for soil to improve its fertility. Soil was exposed to four concentrations of aloin (rich in HAP) for 0, 7, 14 and 28 days. Physico-chemical parameters were analyzed: soil Ph, organic matter (OM), nitrogen, phosphorus, and cation exchange capacity (CEC). The activity of seven enzymes implicated in the C, N and S cycles were measured. Microbial Biomass was determined by the method of substrate induced respiration. BiologEcoplates (Biolog Inc., Hayward, CA) were used to estimate soil microbial functional diversity. Our findings suggested a decrease on phosphorus and nitrogen content and an increase on CEC after aloin addition. Also, a decrease on microbial biomass and enzymes activities was observed, except for FDA. Ecoplates results demonstrate a decrease on microbial activities depending on the incubation time. Moreover, our results indicated that bacterial communities of the tested soils have more affinity to consume substrates as Amino acids and polymers. Our results should be carefully considered in view of the agriculture waists reuse for a sustainable agricultur

Toxicity of the active fraction of Pergularia tomentosa and the aggregation pheromone phenylacetonitrile on Schistocerca gregaria fourth-instar nymph: effects on behavior and acetylcholinesterase activity

Chemical insecticides remain the most used approach in locust control although they present a serious menace to human health and the environment. The search for alternative control methods, efficient and environmentally friendly, has become indispensable. The aim of this work is to study the effect of the aggregation pheromone, phenylacetonitrile, alone or in combination with the active fraction of Pergularia tomentosa on Schistocerca gregaria fourth-instar nymph. Toxicity bioassays showed that the combination of phenylacetonitrile with the active fraction of P. tomentosa significantly increased nymph mortality. Results also showed that the aggregation pheromone caused significant mortality especially after 6 hours of exposure. The pheromone also caused neurotoxic effects on S. gregaria nymph due to the disturbance of the acetylcholinesterase activity. We also noted the presence of cannibalism phenomenon. Phenylacetonitrile seems to have an effect on phase ployphenism of S. gregaria imagos that exhibit specific traits to the solitarious phase

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

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

Biochar amendment alleviates heavy metal phytotoxicity of Medicago sativa grown in polymetallic contaminated soil: Evaluation of metal uptake, plant response and soil properties

Air pollution and soil contamination have caused major environmental damage in the industrial complex of Gabes. This study aimed to evaluate the abilities of biochar to modify soil properties and assess the adaptation of alfalfa (Medicago sativa L.) plants in contaminated soils from the Gabes Region. The experiment was executed with soil samples from three sites (S1, S2 and S3) located at different distances from the industrial zone of Gabes. Additionally, a control soil was included for comparison. Pot experiments were performed under controlled conditions, with or without biochar. After 60 days, the accumulation of heavy metals in plants (roots, shoots and nodules) was determined. Moreover, oxidative stress biomarkers, such as malondialdehyde (MDA) content, glutathione-S-transferase (GST) and catalase (CAT), were evaluated. Soil microbiological properties, including bacterial functional diversity and fluorescein diacetate hydrolytic (FDA) activity, were analyzed, along with soil chemical properties. Our results revealed that biochar supplementation can improve microbial functions and cation-exchange capacity (CEC), thereby increasing the availability of nutrients to plants. Interestingly, the application of biochar resulted in decreased concentrations of copper (Cu) and zinc (Zn) in plants, which may be attributed to a reduction in their bioavailability in the soil. The accumulation of heavy metals in alfalfa organs was positively correlated with the levels of MDA and antioxidant enzymes in both leaves and roots. In this study, the addition of biochar reduced the antioxidant mechanisms of alfalfa and mitigated the negative effects of metals, resulting in a positive impact on growth and chlorophyll content. Our data highlights the beneficial effects of biochar on enhancing crop productivity and remediating contaminated soil