![]() Therefore, the intent of this review is to critically evaluate both types of evidences available to support the nutritional significance of silica for plant stress tolerance and health benefits of dietary silica primarily derived from plant-based foods. There is a need for comprehensive information covering the breadth and versatility of silica. Most of the previously published reviews focused on either aspect of nutritional significance of Si ( Guntzer et al., 2012 Wu et al., 2013 Nielsen, 2014 Zhu and Gong, 2014 Pontigo et al., 2015). Thus Si plays a significant role in modulating physiological and metabolic responses both in plant and human biology. Silica is prevalent in the typical human diet with concentrations tending to be much higher in plant based foods and has a multitude of uses, e.g., strengthen bones and connective tissues, reduces risks of alopecia, Alzheimer’s and cardiovascular diseases ( Jugdaohsingh et al., 2000 Jugdaohsingh, 2007 Nielsen, 2014). During recent years along with the growing interest of plant biologists to understand Si dependencies and anomalies in plants, the nutritional function of Si has also received attention in human biology, where equally important features have been established by now. On the other hand, Si deficiency does not interrupt the life cycle in plants, therefore its absolute requirement and essentiality continues to be debated ( Marschner, 1995). ![]() Investigation of crop species of the Si-accumulating type including cereals revealed an active mode of Si uptake and transport system, which enable them to realize the high Si requirements of their plant body ( Ma et al., 2006, 2011). However, beneficial effects of Si are most obvious in high Si-accumulating plant species ( Ma et al., 2011). Si enhances physical and chemical defense power of plants ( Epstein, 1999). Thus plants face an enormous combinatorial complexity with basically infinite environmental conditions. Plants grown under natural conditions are exposed to diverse biotic (diseases caused by viral and bacterial pathogens or fungi and herbivores) ( Miyake and Takahashi, 1983 Cherif et al., 1994 Savant et al., 1997) and abiotic (salinity, heat, cold, wind, water, and mineral deficiency or excess) stresses, often in combinations ( Ma et al., 2001 Ma, 2004 Farooq et al., 2015). The ample Si supply from soil to plants exceeds uptake of essential nutrients in several species including cereals ( Epstein, 1994). This view is based upon a range of field and laboratory experiments indicating that Si serves manifold roles in plants ( Epstein, 1999, 2009 Rafi and Epstein, 1999 Rains et al., 2006 Ma et al., 2011). ![]() Thus functional significance of Si in modulating growth performance and ameliorating stress in higher plants is widely accepted. Ferns and many monocots accumulate Si to high amounts ( Hodson et al., 2005). However, Si also cycles between plants and the environment thereby realizing multiple functional benefits. Si is required for normal cell growth and imparts structural benefits to diatoms, radiolarians, and some sponges ( Carlisle, 1997). Until 1960s, the essentiality of Si was best known for lower forms of life, in particular diatoms, sponges and corals. Silicon (Si) is omnipresent and takes part in global biogeochemical Si cycles, both in oceans and on terrestrial areas ( Basile-Doelsch et al., 2005). This review aims to provide a broad perspective on Si as important element for plant and human nutrition and to define research fields for interdisciplinary research. Thus the link between Si availability for plant development and its profound implication for human welfare should receive attention. Despite this empiric knowledge, the essentiality of Si still remains enigmatic. Si bioavailability in human diet, e.g., strengthens bones and improves immune response, as well as neuronal and connective tissue health. Likewise, human exposure to Si imparts health benefits and essentially occurs through plant-derived food products. Plant Si plays a pivotal role in growth and development, and this beneficial effect depends usually on accumulation in plant tissues, which are then protected from various forms of biotic and abiotic stresses. During the last three decades, nutritional significance of Si for plant and human health has received increasing attention. Si is highly abundant in soil, and occurs ubiquitously in all organisms including plants and humans. Silicon (Si) serves as bioactive beneficial element. Department of Biochemistry and Physiology of Plants, Faculty of Biology, University of Bielefeld, Bielefeld, Germany.
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