Appraisal of Abelmoschus esculentus L. Response to Aluminum and Barium 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.

Assessment of Tolerance to Lanthanum and Cerium in Helianthus Annuus Plant: Effect on Growth, Mineral Nutrition, and Secondary Metabolism.

Rare earth elements (REEs) present a group of nonessential metals for the growth and development of plants. At high concentrations, they can induce internal stress and disturb the physiological and biochemical mechanisms in plants. The potential uptake of lanthanum (La) and cerium (Ce) by the horticultural plant Helianthus annuus and the effect of these elements on its growth, its absorption of macroelements, and the contents of phenolic compounds and flavonoids were assessed. The plants were exposed to 0, 1, 2.5, 5, and 10 µM of La and Ce for 14 days. The results showed a remarkable accumulation of the two REEs, especially in the roots, which was found to be positively correlated with the total phenolic compound and flavonoid content in the plant shoots and roots. The plant's growth parameter patterns (such as dry weight and water content); the levels of potassium, calcium, and magnesium; and the tolerance index varied with the concentrations of the two studied elements. According to the tolerance index values, H. annuus had more affinity to La than to Ce. Although these metals were accumulated in H. annuus tissues, this Asteraceae plant cannot be considered as a hyperaccumulator species of these two REEs, since the obtained REE content in the plant's upper parts was less than 1000 mg·Kg-1 DW.