Silicon in plant biology: from past to present, and future challenges

Silicon (Si) is the second most abundant element in the Earth's crust after oxygen, and it has wide implications in plant biology. The effects of Si range from regulation of development to protection of plants from various types of stresses. In recent years, much progress has been made in research on the uptake of Si at the root surface, its loading into the xylem, and its transport to various tissues in Si-accumulating plants. However, much still remains to be discovered. For instance, there is currently no direct evidence for the participation of Si in plant metabolism, and little detail is known of the mechanisms by which Si functions in plants. In this special issue, we present a collection of papers that attempt to answer such questions, but we are still a long way from fully understanding the role of Si in plant biology.