moss + lichen

Time to amp up your nature vocabulary!

Moss and lichen are poikilohydric ["POI-kee-loh-hi-drik"] organisms, meaning their inner water content changes with the moisture of their surrounding environment. Uffda!

Poikilohydric organisms have no means to prevent desiccation (drying out completely). When the weather is rainy and damp, for example, mosses soak up the water, allowing them to photosynthesize and grow. But when the environment dries up, so does the moss. Amazingly, mosses and other poikilohydric organisms are able to survive desiccation and live in “water stressed” areas where other herbaceous plants would be unable to survive!

A downside of poikilohydry for moss is (as referenced) that when it dries up it is unable to grow. So is tied to periods where they can access to water. Next time you see a crack in your sidewalk look closer! On the driest summer days the moss might look dead, but they will rehydrate once it rains!

“The process that allows these beings to hover at the boundary between life and death remains a profound mystery that is continually played out in the mosses beneath our feet”
- Robin Wall Kimmerer (Gathering Moss, p.60)

Credit / more info available at https://highparknaturecentre.com/index.php/blog/2018/word-of-the-week-poikilohydric