Plant of the Week

MMMooosssssseeesss When considering plants, mosses are

often overlooked and although many are quite small, they play a vital role in most ecosystems. We usually think of mosses as conspicuous components of wet habitats, rainforests, swamps, creek and river banks, but when you know what to look for, and how to look, you will find mosses in some pretty harsh environments: in deserts; alpine, arctic and subantarctic regions; even round volcanic fumaroles. Don’t forget, they are plants and they do carry out photosynthesis but they produce spores rather than flowers and they don’t have an internal conducting (vascular) system.

Bryophytes are probably more

important than many other divisions of the plant kingdom because of their interaction with water. Mosses are able to hold amazing quantities of moisture between their minute, often finely sculptured, overlapping leaves and fine, massed rhizoids (root like structures). In rainforests, mosses reduce the velocity of water and minimize erosion processes; mosses and liverworts in tree canopies can absorb moisture as if they were giant sponges, humidifying the forest for long periods after rain. In deserts, where they are

Hypnodendron \vitiense subsp. australe

Ptychomnion aciculare

Dawsonia superba

Mosses from Werrikimbe National Park in northern NSW

components of biological soil crusts (complex combinations of algae, fungi, lichens, mosses and liverworts), mosses have the ability to rapidly absorb and store moisture from dew or fog. They stabilize desert soils and protect dunes from erosion by wind and flash flooding. They also contribute to the fertility of desert soils, and enhance the survival of ephemeral, annual and perennial seedlings.

The ancestors of modern day mosses are believed to have moved from the sea

to the land in the late Ordovician ~ 450 million years before present, although the Carboniferous is more usually accepted for origin and expansion of mosses.

Until recently, mosses were considered to be one class (Musci) of the division

Bryophyta of the Plant Kingdom. The other two classes were the liverworts (Hepaticae) and the hornworts (Anthocerotae). Using modern molecular techniques, botanists have now elevated each of these classes to divisions of the plant kingdom, so now only mosses belong to the Division Bryophyta, liverworts are placed in the Division Marchantiophyta and hornworts in the Division Anthocerophyta. All three divisions are now collectively referred to as “Embryophytes”, that is, land plants that do not have a vascular system. Some mosses do have elements of conducting systems, but as they lack lignin, they are not considered to be true “vascular plants”.

There are currently a number of bryophyte studies being undertaken by researchers in the Department of Biological Sciences at Macquarie University. These include a study of bryophyte distribution in Nothofagus moorei forests of northern NSW by Ross Peacock and Alison Downing; taxonomy of the Trematodon, Pohlia, Mniaceae and Sematophyllaceae by Helen Ramsay; studies of bryophytes of biological soil crusts of the Gurbantunggut Desert of north-western China by Alison Downing working with Professor Zhang Yuan Ming and other researchers and students of the Chinese Academy of Sciences; and bryophytes of sub-Antarctic islands (Macquarie Island, Heard Island and Iles Kerguelen) by Patricia Selkirk.

Professor R. D. Seppelt from the Australian Antarctic Division in Hobart, has very kindly allowed us to display some of his scientific illustrations of Australian mosses.

Alison & Kevin Downing, Department of Biological Sciences, 21.05.2012

Nothofagus moorei (Antarctic Beech) forest in Werrikimbe National Park in northern NSW. Mosses

are abundant on beech buttresses, fallen logs and rocks.