The Starset SocietyWhat, exactly, is a plant made of? Scientists have a good understanding of the essential nutrients plants need to grow. But what plants need and what they contain are not necessarily the same.
As plants draw water and nutrients through their roots, they can also absorb other elements from their surroundings. Those elements become incorporated into plant tissues—meaning what’s in the ground can help shape what’s in the plant.
That becomes especially important when the ground isn’t on Earth.
Researchers studying the possibility of growing plants on the moon and Mars want to understand what could happen when their roots encounter regolith, the rocky material rich in metals that covers their surfaces. Growing in a different gravitational environment could also affect what a plant contains—an important consideration if those plants are eventually grown as food.
But understanding those differences first requires a clearer picture of what plants contain here on Earth.
“We needed to answer a space question by learning about Earth,” said Harrison Coker, a doctoral researcher in the Texas A&M University Department of Soil and Crop Sciences within the College of Agriculture and Life Sciences and Dr. Julie Howe’s lab.
Coker and an international team have now helped establish that baseline. In a study and global meta-analysis published in ACS Environmental Au, they compiled measurements from 5,474 plant samples across 73 countries, covering 52 elements, 21 climate classes and 26 soil groups.
The resulting global database provides a more comprehensive picture of plant elemental composition, including dozens of elements beyond the familiar nutrients typically associated with plant growth.
Looking beyond what plants need
As a NASA Space Technology Graduate Research Opportunity fellow, Coker studies ways to support plant growth on the moon and Mars and has spent the past three summers conducting research at NASA’s Kennedy Space Center.
That interest connected Coker with an international group of scientists brought together by the Moon Village Association, an organization focused on the exploration and development of the moon led by former students Dr. Borja Barbero and Rachel Rivero. The group began looking for data on the elemental composition of plants grown in simulated lunar and Martian regolith, but found little to work with.
That led them to a broader issue: plant nutrition research has traditionally centered on essential elements, from familiar macronutrients such as nitrogen, phosphorus and potassium to micronutrients needed in much smaller amounts. But there was far less information bringing together the wider range of elements that are often abundant in soils and may also be present in plant tissues.
Coker said he and his collaborators initially planned to focus on plants growing in extreme environments on Earth. But as the project developed, they broadened their search, gathering published measurements from around the world to capture a much wider range of plants and environments.
More than the essentials
Once the researchers looked beyond the elements plants need to survive, they found some surprising patterns in what plants actually contain.
Twenty elements not considered essential for plant growth were found at higher average concentrations than molybdenum, the essential element found at the lowest concentration in the study.
That finding stood out to Coker.
“What I found fascinating was that at a global scale, several elements not considered essential for plant life had an order of magnitude higher concentration than what is essential,” Coker said. “If these lesser-studied elements are more prevalent than we think, what are the unseen biological roles of these co-occurring elements in a plant?”
For many of these lesser-studied elements, there isn’t yet a clear answer. The study found they collectively make up a considerable portion of plant tissues, giving researchers a broader foundation for investigating what roles some of these elements may play in plants.
The analysis also found a strong evolutionary pattern: Closely related plants tended to have similar elemental profiles, suggesting that different plant lineages have characteristic elemental compositions.
A new reference point
The study notes that plants play an important role in moving elements through ecosystems, taking them up from their surroundings and incorporating them into living tissue. Having a more complete picture of those elements could help scientists better understand those larger cycles.
The database could also allow researchers to incorporate a broader range of elements into global models or use the data to train machine-learning tools that explore relationships between plant composition and ecosystem assembly. In agriculture, the database could provide a reference for studying the elements crops remove from soils and how those elements cycle through agricultural systems.
It also gives researchers a baseline for studying plants in unfamiliar environments, including lunar or Martian regolith. Scientists can compare the elemental composition of those plants with the much broader picture now available for plants on Earth.
But Coker sees the value of the work as extending beyond any one application. By looking beyond the elements already known to be essential, researchers can begin asking more fundamental questions about the many elements found in plant tissues and what roles they may play.
“It’s important to know what life is made of. Once we know all the elements, we can start peering into more intricate processes such as how it all works together to make complex features like function and stability,” Coker said. “Elements are the ingredients of life.”
read more at phys.org
