Metals and seeds: Biochemical and molecular implications and their significance for seed germination

Seeds contain the embryo as a new plant in miniature and have two major functions, reproduction and dispersal. Seed formation completes the process of plant reproduction and, with seed germination, the next plant generation starts. Given the ever-increasing environmental pollution with metal(loid)s, it is perhaps surprising that relatively few reports detail the impacts of metals on seed metabolism, viability and germination in comparison to the numerous publications on the effects of metals in vegetative tissues, particularly roots and shoots. This review provides information on metal(loid) homeostasis, detoxification and tolerance in relation to seed metabolism and performance. The delivery of metals from the mother plant into seeds and their implications on seed development are discussed, as are their uptake upon seed imbibition and subsequent effects on seed germination. Implications for seeds and seedlings on the biochemical and molecular level are discussed and finally, applied aspects are considered regarding the use of seeds for soil and water purification, and in phytoremediation programmes. We conclude with a perspective on future metal research in relation to seed biology.