PLANTS AND SILICON: A MODERN ECOLOGICAL PERSPECTIVE (Invited Presentation)

Understanding how and why plants use silicon is key to exploring the role of vegetation in the silicon biogeochemical cycle today and its changing role over geological timescales. The coupling of the silicon and carbon cycles through terrestrial and marine biological pumps, occlusion of carbon in phytoliths and chemical weathering of mineral silicates highlights the importance of understanding silicon fluxes. With more than half of terrestrial net primary productivity attributed to high silicon-accumulating plants, and a complex evolutionary history of plant silicon uptake capacity apparent, a better understanding of plant silicon function is essential to progress this field. All plants contain some silicon, which they use to defend against herbivores, alleviate the impacts of abiotic stresses and possibly substitute for roles normally filled by carbon. Plant silicon content ranges from 0.1% to more than 10% of plant dry mass, and following plant death, some silicon dissolves, but larger discrete silica bodies (phytoliths) can persist, recording plant presence and silicon function. The last fifteen years has seen a surge in studies exploring how plants use silicon, the evolution and regulation of silicon uptake by plants, and quantification of silicon fluxes in ecosystems. By providing a modern functional and ecological perspective, including data from recent meta-analyses on the role of silicon in stress alleviation and herbivore defence, I will explore plant use of silicon. There remains enormous potential to combine data from agricultural, ecological and palaeontological approaches to develop our understanding of the significant role plants play in silicon biogeochemical cycles today and in the past.