Wild Grass Releases a Variety of Particles into the Air over Its Life Cycle

Fungal spores are found to be most abundant during initial growth, while bacteria predominate during flowering and fruit development.

The Science

Living organisms release particles such as fungal spores, pollen, bacteria, viruses, algae, and cell debris. In the atmosphere, these biological particles can act as nuclei for cloud droplets and ice crystals. On plants, ice nucleating bacteria can influence frost injury; microbes can either promote plant growth or cause infection that reduce plant growth. The aboveground parts of plants, mainly stems and leaves, are one of the most prevalent microbial habitats on Earth, yet little is known about how this microbiome changes throughout a plant’s life cycle. Led by scientists from the Environmental Molecular Sciences Laboratory (EMSL), a U.S. Department of Energy (DOE) Office of Science user facility, a multi-institutional team reports the first characterization of biological particles produced by Brachypodium distachyon, a wild but commonly used model grass, over its life cycle.

The Impact

Understanding differences in the type and chemical composition of biological particles during the plant life cycle provides more accurate and reliable insights on structural, functional, and biochemical properties of plant systems, as well as their interactions with microbial communities. This study also provides insights into Earth geoscience system models that represent primary biological particle emissions from the biosphere.


A team of scientists characterized primary biological particles produced by the leaves and stems of the grass Brachypodium distachyon, a common model for energy and food crops, throughout its life cycle. They collected particles at eight different developmental stages, from leaf development to the last season of plant life. Then they analyzed particle morphology, elemental composition, and abundance of functional groups using various types of microspectroscopy platforms. Computer-controlled scanning electron microscopy (SEM) with energy-dispersive X-ray and environmental scanning electron microscopy analyses were performed at EMSL as part of the user facility’s Molecular Bioimaging Integrated Research Platform.

In their analysis, the researchers distinguished spores, bacteria, plant fragments, and other types of biological particles in the plants’ leaves and stems. Fungal spores were most abundant during the stage just before flowering, while bacteria were most abundant during the flowering and fruit development stages. By highlighting the type and abundance of microbial community composition of plant aboveground tissues, this study’s outcomes could lead to a better and predictive understanding of various physiological and environmental factors that influence microbial interactions in these tissues. The results also point to the importance of continued characterization of biological particles from the phyllosphere to further understand the environmental implications.

Principal Investigator(s)

Swarup China
Pacific Northwest National Laboratory

Alex Laskin
Purdue University


Office of Biological and Environmental Research, within the U.S. Department of Energy (DOE) Office of Science, for the Environmental Molecular Sciences Laboratory (EMSL) and Atmospheric System Research program; Laboratory Directed Research and Development program at Pacific Northwest National Laboratory for the iPASS, PREMIS, and Chemical Imaging Initiatives; and Office of Basic Energy Sciences, within the Office of Science, for beamtime at the Advanced Light Source at Lawrence Berkeley National Laboratory.


China, S. et al.Microanalysis of primary biological particles from model grass over its life cycle,” ACS Earth and Space Chemistry 4(10), 1895–1905 (2020). [DOI:10.1021/acsearthspacechem.0c00144]