Video: This desert moss can water itself with fog

To tap into scarce water supplies, most desert plants have extensive root systems that burrow deep or spread wide. But one desert moss has a different trick up its sleeve: a thirst-quenching structure called an awn. Awns are tiny, hairlike structures that project from the end of each leaf to capture water (above). For the first time, scientists have examined in detail how this moss (Syntrichia caninervis) pulls water right from the air using its awns. At the smallest scale, the awns are covered with grooves about 100 nanometers deep and 200 nanometers wide, the perfect size for dew to condense within them when conditions are right. Those nanogrooves lie within larger troughs that measure about 1.5 micrometers deep and 3 micrometers wide, a good size to snag fog droplets from the air. Once enough moisture collects in the microgrooves, capillary action caused by surface tension in the water pulls the droplets toward the thicker end of the awn, which lies toward the plant. Voila! The plant waters itself. And on the rare occasions when rain falls, any droplets trapped between two awns are likewise pulled toward the plant’s leaves, the researchers report online today in Nature Plants. These tricks may one day help engineers design better equipment to collect water in arid locales, the researchers suggest.