Aluminum (Al) is an ubiquitously present element in soil; it is considered as a major problem in crop production that affects plant growth and development on acid soils. The aim of this work was to determine the germination parameters, to quantify the water status and growth, to assess the Al accumulation, and antioxidant enzyme activities in plants to evaluate the stress exerted by aluminum in Cucumis sativus L. For germination test, increasing doses of Al were used (0, 200, 500, 1,000, and 2,000 μM). Results showed that germination was stimulated with 500 of Al. Aluminum effects on development were studied by treating the plants with different concentrations of Al (100, 200, 300, and 500 µM, Al) during 45 days. As regards to the plant's growth, water content, and dry biomass production there was a slight increase. On the other hand, the activities of the antioxidant enzymes were disturbed by aluminum stress. Data indicate that the catalase (CAT) activity showed a decrease in the different parts of the plant. However, guaiacol peroxidase (GPX) and ascorbate peroxidase (APX) activities were significantly stimulated. Studying the effects of Al‐induced stress allowed us to conclude that cucumber has a high ability to accumulate this element in the roots.

Barium (Ba) is a nonessential element that can cause several deleterious effects in most organisms. Elevated Ba concentrations can be toxic for plants and may affect growth and disturbances in homeostasis. This study aimed to evaluate the Ba stress, the plant‐tolerance limits, and the detoxification strategy adopted by Cucumis sativus L. The effect of Ba on seed's germination and vegetative development of this species was evaluated. For germination test, different Ba concentrations were used (0, 200, 500, 1,000, and 2,000 μM). Results showed that germination was stimulated with 500 and 2,000 µM of Ba. The toxicity effect on plant development was studied by treating the plants with increasing doses of Ba (100, 200, 300, and 500 μM) during 45 days. Shoot and root dry biomass production decreased significantly with elevated Ba concentrations, although water content enhanced in the roots. The concentration of Ba, 500 µM, induced high Ba accumulation in shoots and roots (9 times higher than in the control plants). Moreover, results showed that catalase, guaiacol peroxidase, and ascorbate peroxidase activities were stimulated in the different tissues of cucumber plants which highlight the occurring of an oxidative damage through Ba treatments and the involvement of the plant enzymatic antioxidant defense system.

The question of trace metal elements (TME) is still relevant and causes several environmental problems. Moreover, the digestion methods of TME have a significant impact on ecosystems. Sample preparation is an important step of any analytical procedure. In fact, defining the levels of TME in vegetal tissues requires various steps: drying samples, crushing, extraction, and dosage. The use of chemical extraction solutions can be put into question. Other than their lack of specificity, they are susceptible to provoking the redistribution and/or re-fixation of a part of the metallic ions between the various vegetal components. Our study aims to test the procedures of extraction that are specific for the metals Cu, Zn, Fe, Ca, Cr and Ba. Our results show an outstanding difference in the levels of TME derived from the same vegetal sample, according to the various techniques of extraction. In fact, cold extraction by nitric acid diluted at 10% is the most efficient way to put the ions of Cu, Zn, Fe and Ca into a solution. Meanwhile, the use of heated extraction using different acid digestion approaches is the most efficient for Cr and Ba solubilization from Atriplex portulacoides, Arthrocnemum indicum, Olea europaea BCR-62, Ulva lactuca and Ulva lactuca BCR-279.

Trace metal elements (TMEs) are among the most important types of pollutants in the environment. Therefore, a precise determination of these contaminants in several environmental components is required for the safety assurance of living organisms. Spectroscopic analysis is an efficient technique employed to detect and determine TME contents in numerous samples. Hence, to achieve reliable and accurate results when using spectroscopic analysis, samples should be carefully prepared. In the present study, the comparison of eight digestion methods of five vegetal samples was carried out to quantify Cd, Mn, Al and Mg contents using the atomic absorption spectroscopy technique. According to the extraction techniques used in this study, results showed an outstanding difference in TME levels determined in the same vegetal sample. The results obtained indicated that the highest Mn concentrations were recorded when using the mixture of HNO3-HClO4 in the studied species: atriplex portulacoides, arthrocnemum indicum, olea europaea BCR-62, ulva lactuca and ulva lactuca BCR-279 compared to all other methods. Regarding the extraction of Cd, our results showed that heated extraction using different acids (HNO3-H2SO4-HClO4, HCl-HNO3, HNO3-HClO4, HNO3-H2SO4, HNO3-HCl-HClO4 and HNO3-HCl-H2SO4) was the most efficient in atriplex portulacoides, arthrocnemum indicum, olea europaea BCR-62, ulva lactuca and ulva lactuca BCR-279. Similarly, these heated acid digestion techniques (efficient for Cd) showed the highest levels of Al in atriplex portulacoides and arthrocnemum indicum. However, for the Mg extraction, our results revealed that the effectiveness of the method used depended on the plant species studied. Regarding these findings, the efficiency of metal quantification by AAS depends on the digestion procedure, the metallic ion to determine and the plant species.

In the present work, the effectiveness of chlorophyll a fluorescence as a quick tool to detect the effect of Pb–stress on Limbarda crithmoides and Helianthus annuus species, when exposed to increasing Pb concentrations (0–500 µmol.L–1) for 45 days, was evaluated. The chlorophyll level in plant leaves, as well as the fresh weight and Pb content in the shoots and roots in both plant species, were also determined. L. crithmoides did not show any significant variation in photochemical quenching parameters and energy fluxes in all Pb concentrations despite the change in OJIP plot of 100 µmol.L–1 Pb. In addition, a significant increase in chlorophyll a content was noted along with an increase in the biomass production. However, in H. annuus, Pb stress increased energy absorption, dissipation and trapping and decreased energy transport and electron transport rate. In addition, the OJIP curve showed a notable modification at 300 and 500 µmol.L–1 Pb, without significant changes in the chlorophyll contents and in the biomass production under all Pb concentrations. Results also revealed that Pb was accumulated in the shoots and roots of L. crithmoides and H. annuus and the accumulation was more notorious in the roots of the treated plants. Lead exhibited different influence on the photosystem II performance in both species, thus, the evaluation of chlorophyll fluorescence was a very efficacious tool to reflect the physiological status of L. crithmoides and H. annuus under Pb stress.

Trace metal element (TME) pollution is a major threat to plants, animals and humans. Agricultural products contaminated with metals may pose health risks for people; therefore, international standards have been established by the FAO/WHO to ensure food safety as well as the possibility of crop production in contaminated soils. This study aimed to assess the accumulating potential of aluminum and barium in the roots, shoots and fruits of Abelmoschus esculentus L., and their effect on growth and mineral nutrition. The content of proline and some secondary metabolites was also evaluated. After treating okra plants with aluminum/barium (0, 100, 200, 400 and 600 µM) for 45 days, the results showed that Al stimulated the dry biomass production, whereas Ba negatively affected the growth and the fructification yield. The okra plants retained both elements and exhibited a preferential accumulation in the roots following the sequence: roots ˃ shoots ˃ fruits, which is interesting for phytostabilization purposes. Al or Ba exposure induced a decline in mineral uptake (K, Ca, Mg, Zn and Fe), especially in roots and shoots. In order to cope with the stress conditions, the okra plants enhanced their proline and total phenol amounts, offering better adaptability to stress.