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Abstract: The term phytoremediation is used to describe the clean-up of heavy metals from contaminated soils by plants. In this study, we examined cadmium (Cd) accumulation by Brassica napus in comparison with the known Cd-hyperaccumulator Brassica juncea, in a hydroponic medium. Cd treatment was applied as a concentration series between 0 and 50μM for 15 days. Most of the Cd taken up was retained in roots in both species, however, B. juncea accumulated more Cd in the shoots compared to B. napus. Excess metal supply resulted in an increase in the lipid content of B. juncea leaves grown under cadmium treatment, but did not affect fatty acids composition. In contrast, an alteration in the lipid composition of B. napus leaves was observed together with a decrease in the lipid contents. The amounts of chloroplastic lipids: monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), sulfolipids (SL) and phosphatidylglycerol (PG) decreased drastically under the effect of metallic treatments. Whereas, amounts of extrachloroplastic lipids: phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were significantly increased. The latter finding suggested that PC and PE synthesis was enhanced by metal application. Moreover, the levels of polyunsaturated fatty acids mainly linolenic acid (C18:3) and hexadecatrienoïc acid (C16:3) and that of trans palmitoleic acid (C16:1t) from PG declined. So, cadmium seems to affect preferentially chloroplastic lipids containing higher levels of polyunsaturated fatty acids. Lipid changes in B. juncea, the well known Cd-hyperaccumulator specie, revealed a more stability of its cellular membranes to cadmium-stress as compared to Cd-sensitive specie, B. napus. [Copyright &y& Elsevier]

Pretreatment in arboriculture is a new physiological approach allowing the improvement of plant tolerance to salt stress. This research aims to screen various pretreatments of salicylic acid (SA) and/or calcium chloride (CaCl 2 ) to mitigate the effect of salinity on ‘Oueslati ’ olive plants ( Olea europeae L.) on physiological attributes under 200 mmol L −1 of NaCl application. One - year- old plants were transplanted to sand culture in a greenhouse, and were pretreated with two levels of foliar application of SA (0.5 and 1 mmol L −1 ) and by adding CaCl 2 (10 and 20 mmol L −1 ) to the culture solution twice a week for 45 days. At the end of the pretreatment, the plants were subjected to 200 mmol L −1 NaCl exposure for 75 days. The result showed that shoots and roots growth were decreased significantly due to salinity, sodium (Na + ) ions increased and K + /Na + ratio decreased in leaves. Rate of assimilation ( A ), transpiration ( E ) and stomatal conductance ( g s ) decreased in leaves. Salinity caused significant increase in both malondialdehyde (MDA) and H 2 O 2 concentration, a decrease in total polyphenol and flavonoid levels and an increase in scavenging activity (IC50) (21%). Moreover, salinity caused a decrease in xylem and an increase in phloem thickness in leaves. However, pretreatments could partly improve the adverse effects of salinity on the most studied parameters. SA (1 mmol L −1 ) is able to restrict Na + ions transport from the roots to the leaves limiting its toxicity in the sensitive organs. SA (1 mmol L −1 ) and CaCl 2 (10 mmol L −1 ) pretreatment alleviate the effects of salinity on dry weight of shoots and roots as well as, photosynthetic activity in pretreated plants. Moreover, at the same pretreatment, results showed a decrease of the Na + translocation to the leaves. Furthermore, it has been shown that pretreatment of ‘Oueslati’ olive plants enhance the non-enzymatic antioxidant activity (total polyphenol and flavonoid content).These results suggest that pretreatments may be useful methods to increase salt tolerance in olive, for use in arid and semi-arid environments. [ABSTRACT FROM AUTHOR]