LLeeppiiddoozzaammiiaa ppeerrooffffsskkyyaannaa -- AA ccyyccaadd ffrroomm tthhee ttrrooppiiccaall eeaasstt ccooaasstt ooff AAuussttrraalliiaa

What looks like a palm, grows in tropical rainforests along the coast of northern and south-eastern , but isn’t a palm? peroffskyana – a , of course!

Cycads are an, ancient group of , first recorded from the Permian, 280 million years ago. Palms, in contrast, are relatively recent arrivals, from the Cretaceous ~ 83 – 76 million years ago1.

Cycads, which produce cones, are more closely related to conifers (pines, cedars, cypress) than they are to palms. Their growth habit has changed little since the Jurassic when they were abundant and widespread, so extant species still look like their fossil ancestors. Lepidozamia belongs to the family , which evolved in the mid- Triassic; distribution of fossils includes genera in North and South America, L. hopei Europe, and Antarctica, indicating that this family of cycads evolved prior to the breakup of Pangea1.

L. peroffskyana There are two species of Lepidozamia, both of which occur in Australia. Lepidozamia peroffskyana in NE NSW, and L. hopei in far N. Queensland2. Nostoc is a cyanobacterium (blue-green alga) which has been recorded in all genera of extant (living, modern day) cycads and has the potential to fix atmospheric nitrogen. In addition to normal roots that grow downwards, cycads, including Lepidozamia species, have roots that grow upwards, towards the soil surface; these are known as ‘apogeotropic’ roots. If apogeotropic roots are colonised by the cyanobacterium Nostoc, they are then known as ‘coralloid’ roots because of their uncanny resemblance to coral. This can be seen as a very dark blue/green band within the coralloid roots. Nostoc fixes atmospheric nitrogen for the cycad which supplies carbon and ‘accommodation’ for the Nostoc.

Nitrogen is an essential component of proteins and yet nitrogen is one of the most limited nutrients on earth although it comprises just under 4/5 of the Earth’s atmosphere. Biologically fixed nitrogen contributes up to 90% of N available for use by plants and animals, hence the importance of N fixation by cyanobacterium in the relationship between cycads and Nostoc.

There are implications for people, however. Nostoc produces a neurotoxin in the seeds of cycads. Although most ethnic communities know how to treat and prepare seeds so that toxins are removed, it is still possible to contract neurological diseases by eating bats that have eaten cycad seeds1. If you would like to know more about cycads, go to “The Cycad Pages” maintained by the Royal Botanic Gardens, Sydney: http://plantnet.rbgsyd.nsw.gov.au/PlantNet/cycad/index.html Map: modified from Ken Hill, 17.03.2013. The Cycad Pages, Royal Botanic Gardens, Sydney: http://plantnet.rbgsyd.nsw.gov.au/cgi-bin/cycadpg?taxname=Lepidozamia+peroffskyana 1 Wikipedia: http://en.wikipedia.org/wiki/Cycad 2 Ken Hill, The Cycad Pages, Royal Botanic Gardens, Sydney: http://plantnet.rbgsyd.nsw.gov.au/cgi-bin/cycadpg?taxname=Lepidozamia+peroffskyana http://plantnet.rbgsyd.nsw.gov.au/cgi-bin/cycadpg?taxname=Lepidozamia+hopei

Alison Downing, Kevin Downing & Brian Atwell, Department of Biological Sciences, 25th March 2013

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