The ultimate water collection toolkit of a moss

Researchers Zhao Pan, William G. Pitt, Yuanming Zhang, Nan Wu, Ye Tao and Tadd T. Truscott from the Department of Mechanical and Aerospace Engineering, Utah State University have discovered that moss Syntrichia caninervis has the ultimate water collection toolkit. The moss uses its leaves in ingeneous ways to collect moisture. 

The researchers show that the unique multiscale structures of the hair of moss are equipped to collect and transport water in four modes: nucleation of water droplets and films on the leaf hair from humid atmospheres; collection of fog droplets on leaf hairs; collection of splash water from raindrops; and transportation of the acquired water to the leaf itself. Fluid nucleation is accomplished in nanostructures, whereas fog droplets are gathered in areas where a high density of small barbs are present and then quickly transported to the leaf at the base of the hair. Their observations reveal nature's optimization of water collection by coupling relevant multiscale physical plant structures with multiscale sources of water.

The key to the plant's success is its small leaf hair point, or awn. These 0.5-2 mm-long hair-like structures at the tip of each leaf function like a Swiss Army knife in their ability to collect water from a variety of size scales. Whether the plant gets buckets of rain or only the occasional passing fog, the awn of S. caninervis can exploit any available water resource using four specialized tools.

Each awn is covered in nano- and micro-scale grooves where water vapor will readily condense. The grooves are just the right size and shape to condense water molecules directly from moist air and to catch microscopic fog droplets. At a larger scale, each awn also features elongated barbs that serve as collection depots where condensed or collected water forms small droplets. When large enough, the droplets move along the length of the awn toward the leaf -- sometimes at impressive speeds.

This process of water collection, droplet formation, and rapid transportation to the leaf is a critical function of the awns required to keep this moss alive. S. caninervis is unique because its leaf surfaces must be wet for photosynthesis to occur, and its root-like structures (rhizoids) do not collect water from the soil.

The researchers add "There are several exciting angles to this research. For example, there are processes in industry where we need to extract moisture from a humid environment. It might be possible to create a man-made version of the nano- and micro-scale grooves we see in the awns and use that in a manufacturing setting."

Another attraction is the plant's remarkable anti-splash properties. For several years researchers have been exploring methods to reduce splashing in multiple settings, including the common urinal. The concept is no trivial topic for the Splash Lab team. They've demonstrated that urinal splash-back is a legitimate concern when it comes to public hygiene and facility maintenance costs. The way clusters of S. caninervis harness water droplets inspired a newly designed urinal splash pad being developed by Truscott's Team.

Details of the research appears in the latest issue of journal Nature Plants