Bryophytes

What are Bryophytes?

Some basic information on these small and enigmatic plants.
These pages will be completed as a part of the Madbryo project, focusing on Malagasy plants.

Bryophytes are ...

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Small, terrestrial plants that reproduce by spores but lack the specialized tissues containing lignin that allow other plants to grow much larger

  • Most bryophytes are a few millimeters to a few centimeters tall, however some mosses can reach up to one meter in height.
  • Bryophytes grow on a variety of substrates and can be terrestrial, saxicolous, epiphytic, aquatic, etc.
  • Bryophytes belong to three major lineages:
  • They were probably the first plants with aerial dispersal, as shown by Ordovician spores.
The most ancient trace of aerial dispersal : first early Middle Ordovician spores, c. 473–471  million yr ago from Argentina (ancient eastern Gondwana).  Bar, 20 µm. From Rubinstein et al., 2010. 
Other spores from Ordovician 463–461 million yr ago were found in Saudi Arabia (Wellman et al., 2003).

Resurrection plants

In contrast to most other plants and animals, many bryophytes can survive complete desiccation, without dying. Once rehydrated they are able to recover their normal metabolism including photosynthesis etc.

This remarkable property is necessary because
  • Bryophyte leaves have a thin cuticule, meaning they rapidly gain and lose water and equilibriate with their environment (poikilohydry)
  • However they also have various physiological and morphological adaptations to delay water loss and mitigate damage due to water stress:
    • Most bryophytes have a large water capacity (% of wet mass relative to dry mass)
    • They can produce proteins and other organic compounds that help protect cell membranes from damage during desiccation and rehydration.
Moss stems from Malagasy Pottiaceae and Thuidiaceae (sporophyte), rehydrating in the field.
    • They are also able to efficiently repair any damage caused by drying and recover quickly upon rehydration.

Revival from dessication, physiological evidence

Many bryophytes have stems and leaves—but some have a thallus instead

Bryophytes with stems and leaves: mosses and leafy liverworts. Bryophytes with a thalloid habit or undifferentiated lamina, generally green and chlorophyllose (no stems, no leaves).
Mini bryophyte landscape
In this miniature landscape, a few centimeters wide, the three lineages of bryophytes coexist, both habits are illustrated, leafy and thalloid.
Th = hornwort (always thalloid)
Mo = mosses (always leafy)
LLi = leafy liverworts (some liverworts are thalloid as well)

On a granite slab along national road N7, Ambositra, Madagascar.

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