Syntrichia caninervis, a moss in the Pottiaceae family sometimes called steppe screw moss, is an extremophile that thrives in physically hostile environments. Distributed across arid and semi-arid regions globally, it has adapted to survive harsh conditions that would be lethal to most other plants, including high temperatures and prolonged drought.
Physical Characteristics and Habitat
Syntrichia caninervis is a small moss that grows in dense tufts or cushions, often forming extensive carpets on the soil. When dry, these cushions appear blackish or olive-green. The leaves are about 1 to 2.5 millimeters long, folding against the stem for a compact look. Upon receiving moisture, the leaves spread outwards, and the plant regains a vibrant green hue.
A defining feature is the long, white, hair-like tip, or awn, that extends from each leaf. These awns give the moss a frosted appearance when dry and play a role in water collection by capturing moisture from dew, fog, and rain.
This moss is found in the colder deserts of North America, Asia, Europe, and Antarctica. It grows on various substrates, including soil and rocks, thriving at moderate to high elevations where water is scarce.
Extreme Survival Mechanisms
The primary trait of Syntrichia caninervis is its status as a “resurrection plant,” defined by its tolerance to desiccation. It can lose up to 98% of its cellular water and then fully recover its physiological functions within minutes of rehydration.
When drying, the moss’s leaves curl and fold tightly inward. This movement shields the photosynthetic structures within the leaf from intense sunlight and heat, as the plant enters a state of suspended animation.
Upon rehydration, the transformation is rapid as the dry leaves quickly unfurl. Photosynthetic activity resumes almost immediately, allowing the moss to take advantage of brief and unpredictable rainfall.
Cellular and Genetic Resilience
The ability of Syntrichia caninervis to resurrect itself is supported by cellular and genetic mechanisms. As the moss dries, its cells accumulate protective sugars, such as sucrose and trehalose, and specialized Late Embryogenesis Abundant (LEA) proteins. These substances transform the cell’s cytoplasm into a glassy state known as vitrification, which protects cellular structures from mechanical stress.
Desiccation causes significant damage to a cell’s DNA. This moss possesses an efficient DNA repair system that begins work almost immediately upon rehydration, mending the breaks in its genetic material that occur during the dry state.
The moss also produces antioxidant compounds to combat oxidative stress during drying and rehydration cycles. These molecules neutralize harmful reactive oxygen species. The moss’s genetic blueprint contains an expanded number of genes related to stress tolerance, and research has revealed its ability to withstand extreme cold, surviving temperatures as low as -196°C, and high levels of gamma radiation.
Scientific and Ecological Significance
Syntrichia caninervis is a primary component of biological soil crusts, or biocrusts, in desert ecosystems. The dense carpets it forms help bind soil particles, reducing wind and water erosion. These crusts also enhance soil fertility by increasing water retention and contributing to nutrient cycles.
The moss’s survival strategies make it a model organism for research into desiccation tolerance. Understanding how it protects its cells could lead to new methods for preserving medical supplies, such as vaccines or blood products, without refrigeration.
The genes for its drought resistance could be used in agricultural biotechnology to engineer crops that are more resilient to drought. The moss’s resilience has also led to it being studied as a pioneer plant for colonizing extraterrestrial environments, such as Mars.