Chelator-buffered nutrient solution is ineffective in extracting Ni from seeds of Alyssum

Hyperaccumulator species of the genera Alyssum can accumulate 100 times more Ni than normal crops and are therefore used for phytomining and phytoextraction of nickel contaminated soils. Basic studies on the physiology and metal uptake mechanisms of these plants are needed to increase efficiency and uptake capacity of Nickel (Ni) by hyperaccumulators. Recent attempts to disclose if those hyperaccumulator species require higher Ni level than normal plants failed because of the high Ni content in the seeds (7000-9000 microg g(-1)). In this study, we attempted to use chelator buffered nutrient solution to deplete Ni from the seed/seed coat and to obtain low Ni seedlings of Alyssum cultivars to be used in physiology studies. HEDTA-buffered nutrient solution did not deplete Ni from the seeds, perhaps because Ni was mainly localized within the seedling embryonic tissues with greatest Ni enrichment in the cotyledons and hypocotyls. We could not observe any positive correlation between seed fitness and germination capacity with seed Ni content. Investigation of nickel localization in Alyssum seeds using synchrotron X-ray microfluorescence (micro-SXRF) showed that nickel is localized in the embryonic tissues with greatest Ni enrichment observed in the cotyledons and hypocotyl.