A new code to decipher phytoliths

Plants don’t have skeletons, but they still have a mineral component in them. Inside plants you can find phytoliths, microscopic mineral deposits that a plant forms from silica. Because these are mineral, when a plant rots away, its phytoliths persist. Luc Vrydaghs, one of members of the International Committee for Phytolith Taxonomy, explained that these easily overlooked fragments are of great value to many people. He said: “A wide range of researchers, from archaeologists, geoarchaeologists; paleontologists, and geochemists to plant systematists, ethnobotanists and molecular biologists use phytoliths in their work. They analyze phytoliths to better understand such things as the past use and domestication of plants, how vegetation and ecosystems have changed through time, or how and why plants take up and deposit silica in their tissues.”

Phytolith
Phytoliths extracted from plant material (Elephant Grass). Image: Benjamen Gadet / Wikipedia.

One of the great strengths of phytoliths, their variation, has also meant that clear description is important for research. But do people mean the same thing when they use the same words? To ensure they do, there is an International Code for Phytolith Nomenclature, now in its second version. The International Committee on Phytolith Taxonomy (ICPT) said: “Recognizing the need for a standard language and code for naming and describing phytoliths, the discipline commissioned a committee to create the International Code for Phytolith Nomenclature 1.0 (ICPN 1.0). After its 2005 publication in the Annals of Botany, ICPN 1.0 gradually became the standard in the discipline and today is arguably the most widely utilized and cited paradigm for naming and describing phytoliths. Although ICPN 1.0 moved the discipline a long ways towards standardizing the terminology and procedures used by researchers, more than a decade of use demonstrated the need to revise, update, and improve it. To address the need, the International Phytolith Society formed a new committee to make the revisions. ICPN 2.0 is the result of that effort. Its publication has been anxiously awaited by researchers.”

The code promises to be of great use among scientists in diverse disciplines. The ICPT said: “Researchers in an ever-increasing number of disciplines are finding phytolith analysis a useful tool. For example, while environmental scientists have long used phytolith analyses to study vegetation and environmental changes that have occurred during the last few 100,000 years, recently, paleontologists have begun to analyze phytoliths to study the evolution of plants and vegetation change that occurred many tens to hundreds of millions of years ago. That has fostered a great interest among botanists in the question of why phytoliths form in some taxa. For example, are they an adaptation to such things as herbivory or drought? If so, how can that knowledge be used to improve modern agriculture? That question in turn has led molecular biologists to study how phytoliths form inside plants in the first place, and what are the genetic controls?

“Other examples of relatively recent applications of phytolith analysis include climate change researchers who are studying to what degree phytoliths can store carbon and whether they could play a role in mitigating climate change, and soil micromorphologists who study phytoliths to better understand soil depositional histories. Many more examples of an expanding use of phytolith research exist, all of which illustrate the need for this standardized terminology and protocol for communicating among disciplines.”

ICPN 2.0 is a much anticipated revision of ICPN 1.0. The ICPT said: “The revisions in ICPN 2.0 are informed by feedback from a decade of use of ICPN 1.0, the work of phytolith scientists since 2005, and the need to accommodate the ever-expanding range of disciplines conducting phytolith analysis. Thus it is, and we anticipate will continue to be, a steady process of iteration over the years. Indeed, ICPN 1.0 was named 1.0 precisely because the authors recognized that the code would need to be a dynamic and ever-improving work in progress”

While ICPN 2.0 marks a new chapter in phytolith research, the committee is hopeful that this will be stepping stone to an ICPN 3.0. The ICPT concluded: “Although small changes to ICPN 2.0, for example new words added to the glossary, may not merit an entirely new publication, there will certainly be new discoveries and issues that will demand an ICPN 3.0 and more. Perhaps ICPN 2.0 will meet the needs of the phytolith community for a decade or two, but considering the rapid growth of, and improvements in the discipline, it is difficult to speculate.”

Further reading

International Committee for Phytolith Taxonomy (ICPT). (2019). International Code for Phytolith Nomenclature (ICPN) 2.0. Annals of Botany. https://doi.org/10.1093/aob/mcz064