Potential Phytoextraction with in-vitro regenerated plantlets of Brassica juncea (L.) Czern. in presence of CdCl$_2$: Cadmium accumulation and physiological parameter measurement

Heavy metal contamination of agricultural land is partly responsible for limiting crop productivity. Cd is known as a non-essentiel HM that can be harmful to plants even at low concentrations. Brassica juncea (L.) is able to accumulate more than 400 μg.g D.W. in the shoot, a physiological trait which may be exploited for the phytoremediation of contaminated soils and waters. In our study, we have subjected regenerated plantlets obtained by the means of transverse thin cell layer technology from hypocotyl of B. juncea in the presence of 150 μM CdCl2 to a second stress of CdCl2 (75 μM), applied hydroponically for 3 days, to show whether the in-vitro plantlets were able to accumulate more Cd than wild type (plantlets obtained in the absence of 150 μM CdCl2, and hence argue about their potential use in the phytoextraction process. The application of 75 μM CdCl2 for three days does not show any effect in the B. juncea growth parameters (F.W. and D.W.) whatever the type of plantlets. This application decreases also the contents of chlorophyll a, carotenoids and Chl a/b ratio (2.26) for plantlets regenerated in the absence of CdCl2 but not those of plantlets regenerated in its presence. Moreover, the amounts of MDA were increased in all plantlets however even more in those obtained in the presence of CdCl2. Cd contents were higher in the plantlets regenerated in the absence of 75 μM CdCl2 than those in its presence. Roots have the highest contents (3071; 1544 μg.g D.W.) followed by stems (850; 687μg.g D.W.) and leaves (463; 264μg.g D.W.) respectively. In our conditions, we suggest that the low accumulation in the plantlets regenerated in the presence of CdCl2 by the means of in-vitro regeneration technology is still benefical, to some extent, for the phytoextraction process and seems to be an interesting technology that allows the cultivation of these plantlets in contaminated soils with low accumulation of metal in their shoots and probably in their seeds used in many food technologies. This results in decreasing the health risk du to the consumption of the spinoff products.