Julia Cooke

When I first became interested in plant silicon (studying archaeology at the Australian National University in 2001), the number of papers on the topic were limited.  Research was dominated by studies of preserved phytoliths rather than plant silicon use per se, though some seminal papers outlined potential roles of silicon in plants, speculating about further importance.  Today, papers about plant silicon use and function are published weekly if not daily, and biologists are much more aware of silicon as an important element for plants and ecology.

This month sees the publication of two special journal issues on plant silicon function that I’ve been editing with Dr Jane DeGabriel and Prof Sue Hartley.  They highlight the huge, recent progress in understanding functions of silicon in plants as well as plant-soil and plant-animal interactions.  We hope both will inspire future research and provide clear direction.

Functional Ecology: The functional role of silicon in plant biology (Issue 30, volume 8)  features seven review papers, listed below, summarising and exploring aspects of the latest research in plant silicon.  Topics covered include: silicon uptake, the evolution of phytolith production, human appropriation of silicon, silicon as a herbivore defence in ecology, silicon function in aquatic plants, plant silicon and soil evolution and silicon in the alleviation of abiotic stresses.  With Functional Ecology chief editor Ken Thompson, I recorded a podcast about plant silicon for this Special Feature.  Lay summaries of the articles are available here.

Frontiers Research Topic: Plant silicon interactions bweteen organisms and the implications for ecosystems, edited by Jane and I, features nine papers containing brand new data and novel methods.  It includes papers, listed below, about silicon as defensive silicon structures of leaf surfaces, a first look at how elevated CO2 might change plant silicon accumulation, field studies on induced silicon responses to herbivory, element composition of phytoliths, using near infra red spectroscopy to analyse silicon, silicon and endophytes, silicon fertiliser in sugarcane pest resistance, field uptake of silicon in marshes and thinking about silicon beyond grasses.  It will soon be available as a free ebook.

Despite the growth in this field, because silicon is considered a beneficial rather than an essential nutrient for plants, many papers begin with a justification of the importance of silicon for plants.  The content of these two special issues resolutely demonstrate silicon is an element that cannot be ignored in plant biology and ecology. It’s an exciting time to be working in this field. Our editorial for Functional Ecology ends with a call to arms, which I’ll finish with here too, that argues it’s time to move on from having to justify interest this topic and forge ahead with seriously siliceous plant research.

“The same four statements begin many papers in this field, including our own, describing plant Si as: the second most abundant element on the earth’s crust, often overlooked in plant research, comprising up to 10% of plant dry weight, and beneficial but not essential for plants. This journal issue consolidates knowledge of plant Si, demonstrating its diverse functions in plant ecology, irrespective of essentiality.  It shows the scale on which plants impact the global Si cycle and our role in cycle modifications. Hence, we argue that we no longer need to justify our interest in plant Si and can leave stale statements behind.  Let’s instead stand on the shoulders of findings united in these reviews.  Let’s now begin papers with a statement that Si is an important element in plant biology, with complex roles in ecological strategies and in mediating interactions with their environment and other organisms, and leap into new territory from here.”

Functional Ecology: The functional role of silicon in plant biology (Issue 30, Volume 8)

• Editorial: Cooke, J., Hartley, S. and DeGabriel, J.L. (2016) The functional ecology of plant silicon: geoscience to genes. Functional Ecology 30(8):1270-1276
• Deshmukh, R. & Belanger, R.R. (2016) Molecular evolution of aquaporins and silicon influx in plants. Functional Ecology. 30(8): 1277-1285
• Stromberg, C., Di Stillo, V. & Zhaoliang, S. (2016) Functions of phytoliths in vascular plants: an evolutionary perspective. Functional Ecology.30(8): 1286-1297
• Cornelis, J. & Delvaux, B. (2016) Soil processes drive the biological silicon feedback loop. Functional Ecology. 30(8): 1298-1310
• Hartley, S.E. & DeGabriel, J. (2016) The ecology of herbivore-induced silicon defences in grasses. Functional Ecology.30(8): 1311-1322
• Schoelynck, J. & Struyf, E. (2015) Silicon in aquatic vegetation. Functional Ecology. 30(8): 1323-1330
• Carey, J.C. & Fulweiler, R.W. (2015) Human appropriation of biogenic silicon – the increasing role of agriculture. Functional Ecology. 30(8): 1331-1339
• Cooke, J. & Leishman, M.R. (2016) Consistent alleviation of abiotic stress with silicon addition: a meta-analysis. Functional Ecology.30(8): 1340-1353

Frontiers in Plant Sciences: Plant silicon interactions between organisms and the implications for ecosystems (online)

• Editorial: Cooke, J. and DeGabriel, J.L. (2016).Recent advances in the ecology of plant silicon: novel insights into functions, interactions and methods for analysis. Frontiers in Plant Science, 7,1001
• Carey, J.C. & Fulweiler, R.W. (2014) Silica uptake by Spartina – evidence of multiple modes of accumulation from salt marshes around the world. Frontiers in Plant Science, 5, 1–11.
• Fulweiler, R.W., Maguire, T.J., Carey, J.C. & Finzi, A.C. (2015) Does elevated CO2 alter silica uptake in trees? Frontiers in Plant Science, 5, 1–7.
• Hartley, S.E., Fitt, R.N., McLarnon, E.L. & Wade, R.N. (2015) Defending the leaf surface: intra- and inter-specific differences in silicon deposition in grasses in response to damage and silicon supply. Frontiers in Plant Science, 6, 1–8.
• Huitu, O., Forbes, K., Helander, M., Julkunin-Tiitto, R., Lambin, X., Saikkonen, K., Stuart, P., Sulkama, S. & Hartley, S.E. (2014) Silicon, endophytes and secondary metabolites as grass defenses against mammalian herbivores. Frontiers in Plant Science, 5, 1–10.
• Li, Z., Song, Z. & Cornelis, J. (2014) Impact of rice cultivar and organ on elemental composition of phytoliths and the release of bio-available silicon. Frontiers in Plant Science, 5, 1–8.
• Katz, O. (2014) Beyond grasses: the potential benefits of studying silicon accumulation in non-grass species. Frontiers in Plant Science, 5, 1-3.
• Keeping, M.G., Miles, N. & Sewpersad, C. (2014) Silicon reduces impact of plant nitrogen in promoting stalk borer (Eldana saccharina) but not sugarcane thrips (Fulmekiola serrata) infestations in sugarcane. Frontiers in Plant Science, 5, 1–12.
• Quigley, K.M. & Anderson, T.M. (2014) Leaf silica concentration in Serengeti grasses increases with watering but not clipping: insights from a common garden study and literature review. Frontiers in Plant Science, 5, 1–10.
• Smis, A., Murguzur, F.J.A., Struyf, E., Soininen, E.M., Jusdado, J.G.H., Meire, P. & Bråthen, K.A. (2014) Determination of plant silicon content with near infrared reflectance spectroscopy. Frontiers in Plant Science, 5, 1–9.