May Presentation: The Wonderful World of Bryophytes

Andrew Franks is principal botanist with O2 Ecology. He did his initial bryophyte study in the Antarctic beech forests of the Lamington and Border Ranges National Parks. Few studies had previously done in the region. When he began curating the bryophyte collection at the Queensland Herbarium, he found 1300 specimens labelled simply as “moss”, with many more than a 100 years old. There are still about 600 specimens to be identified. He related how one specimen, actually contained nearly 20 different species of moss! It could be considered strange that so little attention has been paid to the Bryophytes as there are more than 900 species in Qld (up to 20000 worldwide) and they are the second most diverse terrestrial plant group after the Angiosperms (flowering plants).

Bryophytes is a collective name for three distinct groups – mosses, hornworts and liverworts. They are defined mostly by what they don’t have. Bryophytes lack flowers and seeds, woody material, roots and a vascular system. They are small, just a few centimetres in height with the largest usually less than 20cm tall. Bryophytes occur in every environment, except marine, from polar areas to deserts with 70 degree temperatures. However they are most often associated with damp shady areas. They tolerate desiccation and some can survive for years without water.  However they do need at least a film of water to reproduce as the sperm need water to swim to the egg to produce the spore producing structure. Paradoxically the spores produced in a capsule in another part of the life cycle need dry air to allow them to spread in the wind. Additionally, fragments of moss can grow into new plants.

Bryophytes are thought to be among some of the earliest land plants dating back at least 400 million years. The two adaptations which allowed them to survive on land were the waxy cuticle [a1] covering helping to retain water and the development of structures to house and protect the gametes (egg and sperm).

Mosses are the most familiar group of bryophytes. They have spirally arranged leaves (mostly). Their leaves are 1 cell thick (mostly).  The main body of the plant is the gametophyte which produces a sporophyte consisting of a seta (stem) with a capsule on top which contains the spores. The spores are released through a mouth rimmed with teeth. Sphagnum moss is the best known genus of moss, as found in peat bogs. It has been used as a fuel, a means of transporting water, to absorb snowmelt, and as an antiseptic wound dressing for centuries including WWI. “Bog bodies”, specimens of human bodies preserved in peat bogs for 2-3 thousand years, have been found intact in recent times.

Leafy Liverworts, which make up 85% of all liverworts, have their leaves arranged in two or three rows. Leaves are often flattened and never have a costa (midrib). The mouth of the capsule is split in four arms which disperse spores. The other 15% are thallose liverworts which have thicker straplike leaves.

Hornworts are the bryophytes probably most closely related to higher order plants in that the sporophyte has chloroplasts and stomata, which are generally lacking in the other bryophyte groups. They closely resemble the thallose liverworts.

 [a1]Bryophytes generally don’t have a waxy cuticle layer but have a thin layer which acts in a similar way.

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