Mosses survive desiccation that would kill vascular plants by tolerating full drying

Evidence

But mosses also inhabit places that dry out, such as rocks exposed to the noonday sun, xeric sand dunes, and even deserts. The branches of a tree can be a desert in the summer and a river in the spring. Only plants that can tolerate this polarity can survive here. The bark of these Oregon oaks is shaggy with Dendroalsia abietinum all year round. The name Dendroalsia translates from scientific Latin to something like “Companion of Trees.” Like others of its kind, beautiful Dendroalsia tolerates these wide swings in moisture, with a suite of evolved adaptations known as poikilohydry. Its life is tied to the comings and goings of water. Poikilohydric plants are remarkable in that the water content of the plant changes with the water content of the environment. When moisture is plentiful, the moss soaks up the water and grows prolifically. But when the air dries, the moss dries with it, eventually becoming completely desiccated. … Such dramatic drying would be fatal to higher plants, which must maintain a fairly constant water content. Their roots, vascular systems, and sophisticated water-conservation mechanisms allow them to resist drying and stay active. Higher plants devote much of their effort to resisting water loss. But when water depletion becomes severe, even these mechanisms are overcome, and the plants wilt and die, like the herbs on my windowsill when I left for vacation. But most mosses are immune to death by drying. For them, desiccation is simply a temporary interruption in life. … Mosses may lose up to 98 percent of their moisture, and still survive to restore themselves when water is replenished. Even after forty years of dehydration in a musty specimen cabinet, mosses have been fully revived after a dunk in a Petri dish. Mosses have a covenant with change; their destiny is linked to the vagaries of rain. They shrink and shrivel while carefully laying the groundwork of their own renewal. They give me faith. — Robin Wall Kimmerer, Gathering Moss, 175

Categorization

• XREF: Poikilohydry versus higher plants’ water-conservation trade-off is precisely the kind of tolerance-tradeoff mechanism that also grounds the disturbance-ecology thread across the polyad; connects to loosening-recovery mechanics in climate-disturbance readings. — connects to: Mosses stay small because they have no water-conducting vascular tissue — Robin Wall Kimmerer, Gathering Moss: A Natural and Cultural…, 89; Anabiotic life persists at a barely perceptible metabolic rate rather than truly ceasing — Robin Wall Kimmerer, Gathering Moss: A Natural and Cultural…, 274; Mosses move water passively by harnessing surface forces rather than expending energy — Robin Wall Kimmerer, Gathering Moss: A Natural and Cultural…, 200
• CANDY: A forty-year-desiccated moss revived by a Petri dish dunk is a strikingly tweetable fact.
• DEEPTHINKING: The ‘covenant with change’ framing reconfigures vulnerability itself as adaptive strategy — an inversion worth sitting with: survival bought not by resisting loss but by fully yielding to it.

Broader Connections

• Mosses move water passively by harnessing surface forces rather than expending energy #expands (0.70) — Robin Wall Kimmerer, Gathering Moss, 200