Category Archives: The Plant Press

Super seaweed?

Seaweeds − best called algae as they are not usually pest plants − are increasingly newsworthy. Browse through Chinatown food stores and they can be found advertised both as tasty additives to Asian cuisine and as healthfoods, providing Omega oils, iodine and potassium supplements to diets. If you find a number from 400 to 407 listed on your chocolate bar, milk drink, can, bottle or jar of food then the substance it denotes comes from a brown or a red alga. These algal additives keep food from separating out and looking “gluggy”.

Algae farm ponds in Whyalla, South Australia, used to produce β-carotene. Photo: CSIRO.

The bright red colour of some canned foods has almost certainly been improved by the addition of an extract of single-celled green algae that have oversized red eyespots made of carotene, similar to the stuff in carrots. It should be listed on the can as 160a.

A while back, information on green algae that can be cultured in order to extract biofuel was newsworthy, although the viability of such a scheme has its sceptics.

Recently, articles appeared about a red alga that lowers methane production by bacteria in ruminant livestock (cattle, sheep, goats) in Australia. Methane far exceeds the warming effects of CO2 on the atmosphere, so any decrease in the contribution of methane to the air by millions of ruminants would be most useful.. There are numerous articles available on this possibility but also some warnings about the alga’s potential toxicity.

Asparagopsis taxiformis (LEFT) and A. armata (RIGHT), Cape Peron, Western Australia. Photo: J. Huisman.

Magnified branches of A. armata: on the left, a fluffy vegetative branch, at right, a specialised, barbed grappling branch. Photo: B. Baldock.

So, what is this new “seaweed star”? A fluffy Red alga, about 250 mm tall, widespread in southern Australian and warm to tropic seas globally, probably introduced to the Mediterranean and Atlantic seas. It is Asparagopsis.

There are possibly 3 species, but one has been recorded only in 1945, so we can concentrate on the two common ones – Asparagopsis taxiformis and A. armata – that are being researched as methane suppressants.

Serious divers will recognise encounters with A. armata, its specialised barbed branches clinging annoyingly to wetsuits. Magnified, the effectiveness of the barbs in dispersing this species that lives attached to other algae – an epiphyte – can be appreciated. A. taxiformis is attached to hard surfaces, and has no barbed branches.

A surprising structural feature of both species is that they are made of threads or filaments, best seen under the microscope at tips of plants before the addition of cells that wrap or corticate the initial threads. These filaments can be found internally, even in mature branches, if a lengthwise section is investigated microscopically.

Asparagopsis armata, apical filaments (LEFT) and section through a mature branch (RIGHT). Photo: B. Baldock.

Perhaps more surprising about the two species is that they are sexual stages only. In Asparagopsis taxiformis both female and male structures are produced on the one plant, i.e. it is monoecious. Asparagopsis armata supposedly has separate male and female plants, a dioecious condition, but some question the reliability of this fact.

Asparagopsis taxiformis under the microscope: egg-shaped, coloured female structures with apical openings (cystocarp, LEFT) and small, cigar-shaped, white male structures near branch ends (spermatangial heads, RIGHT). Photo B. Baldock.

You may know that practically all Red algae have a life cycle that alternates between a sexual stage and an asexual or spore-plant stage. In the case of an Asparagopsis species, the spore stage is tiny, unobtrusive, epiphytic and so different to the sexual stages that originally it was thought to be a separate genus – Falkenbergia. It too has a thread-like construction, but largely lacks the cortication of the sexual phase.

Both stages of Asparagopsis – sexual and asexual – have been identified here and in the Mediterranean. Both sexual and asexual stages produce the methane inhibiting substance, bromoform. As the name implies, bromoform is analogous to chloroform (substitute Cl with Br in the formula). It too has a sweet, antiseptic smell like chloroform and has been synthesised in the past for industrial uses, including as a solvent, fire retardant and sedative. It may however have harmful effects on ozone, if released into the atmosphere, and possible carcinogenic effects.

Falkenbergia rufalanosa, the spore stage of Asparagopsis armata (LEFT), and viewed under a polarising microscope (RIGHT). Photo: B. Baldock.

As an economic retardant to ruminant methane production there are a lot of scientific and economic considerations to be made. Cropping of sporadic, naturally occurring populations of Asparagopsis would not be a viable proposition, but, fortunately plants can be grown vegetatively, so the focus of research now seems to be on aquaculture and the feasibility of doing this in vast saltwater land ponds required for the production of the quantities that would be required.

Commercial interests aside, Asparagopsis, with its intricate anatomy and cryptic life history, remains a fascinating red alga and worthy of investigation.

For additional descriptions and illustrations o species, see the following Algae revealed fact sheets:

  • Falkenbergia – Step 7b and Figs 22-24 in the Filamentous red algae Master Key (2.6mb PDF)
  • Asparagopsis armata (0.7mb PDF)
  • Asparagopsis taxiformis (0.5mb PDF)

Written by State Herbarium Hon. Research Associate Bob Baldock.

Happy National Eucalypt Day 2020!

Eucalyptus pimpiniana​, growing in front of the State Herbarium. Photo: A. Thornhill.

March the 23rd marks National Eucalypt Day (see fact sheet from 2018, 360kb  PDF) in Australia. Prior to COVID-19 the Botanic Gardens and State Herbarium had been preparing for two different eucalypt themed tours at Adelaide Botanic Gardens with State Herbarium and Botanic Gardens staff on the 22 and 23 March 2020. Unfortunately we have been forced to cancel them.

We will reschedule these tours sometime in the future but until then we will share some thoughts about this interesting group of plants that marks the occasion.

The eucalypts are actually three genera of predominantly Australian plants: Angophora, Corymbia and Eucalyptus (see also Australian Plants Society fact sheet, 4.5mb PDF). There are over 800 named species of eucalypts. While the majority of eucalypts are purely native to Australia there are a handful of species that have escaped the continent to the north and are native to Timor, New Guinea, Indonesia and the Philippines. The revised Flora of South Australia treatment for eucalypts was published in 2014 (33.8mb PDF).

May Gibbs Stamp, 2016

The living species that occur outside of Australia have fossil ancestors. In fact, the oldest known eucalypt fossil comes from Patagonia and is 52 million years old. Eucalypt fossil leaves have also been found in New Zealand, estimated to be about 20 million years old. We know though that eucalypts are not now native to either South America or New Zealand so at some point they became extinct in those countries and left Australia with an iconic plant group. An article on The Conversation last year discussed how the eucalypts came to dominate Australia.

The eucalypts gained great popularity through the creative works of May Gibbs in 1920s. These artworks have also been celebrated in Australian Stamps.

May Gibbs Stamp, 1985

It is poorly known that when May Gibbs first came to Australia as a child she first lived in South Australia, including in Norwood for a short time. Her family then moved to Western Australia where she spent most of her formative years. May Gibbs’ most famous characters, the gumnut babies Snugglepot and Cuddlepie, use various parts of eucalypts for their clothes. The most well-known pictures of the gumnut babies sees them sitting in big gumnuts which in fact are Corymbia fruit and not of Eucalyptus, most likely Corymbia ficifolia a native tree of Western Australia, and also a common street tree all around Australia. The hats that the gumnut babies wear are the calyptra (cap) of a eucalypt — petals that have evolved to form a protective bud cap. When a eucalypt flower opens the bud cups are pushed off and hundreds of anthers pop out. To raise public awareness for the Spanish Flu outbreak in 1919 May Gibbs painted a scene of a Kookaburra and a gumnut baby both wearing gum leaf facemasks — apt for our times.

On that note we want to say — Happy Eucalypt Day!

We hope that you stay safe and tucked away in your gumnuts until it is safe to come out.

Compiled by Andrew Thornhill, State Herbarium of South Australia & The University of Adelaide.

The world within

Imagination can run riot when investigating the microscopic anatomy of algae.

A rather beautiful alga from Western Australia (Cryptonemia species) looks relatively ordinary from the outside—but, when tissues are squashed, expelling the unusual internal cells, a new world of cell shapes is revealed under the microscope.

Cryptonemia sp A99478 habit

Cryptonemia sp A99478 ganglionic cells

What does the image of the large central cell remind you of? It is, in fact, of a ganglioid cell, unique to some members of the family Halymeniaceae. It gets its name because of the resemblance to the shape of a type of nerve cell found in animals, but as far as we know, doesn’t transmit impulses along its long arms as happens with animal ganglionic cells. In fact, the scientific literature is silent on its function.

A similarly unusual cell type from the Kallymeniaceae is the stellate cell.

Kallymenia rubra A35870 habit

Kallymenia rubra A35870 stellate cell

It comes from inside membranous blades, in a similar position to that of ganglioid cells of the Halymeniaceae, and has short, radiating arms. Again, nothing is definitive about its function.

For more information about the genera with these cell types look at our Algae Revealed series.

Contributed by State Herbarium Honorary Research Associate Bob Baldock.

Plant of the Month: March 2018

The colourful flowers of Amyema miquelii (box mistletoe), our Plant of the Month for March, 2018, provide an important nectar source for birds and insects at this time of year when few other plants are in flower. It occurs in all Regions of the State with the notable exception of Kangaroo Island (see map on eFloraSA).

Amyema miquelii flowers. Photo J.G. Conran.

Mistletoes are native, woody, hemi-parasitic plants. Their sticky seeds are dispersed by birds and germinate on the branches of trees or shrubs, forming an attachment known as a haustorium that penetrates the wood of their host. They are dependent on the xylem sap of their hosts for water and nutrients but have leaves with chloroplasts to produce their own food by photosynthesis. South Australia has 17 mistletoe species in four genera of the family Loranthaceae. Further information can be found in the 5th edition Flora of South Australia family treatment available here (3 MB pdf).

Mistletoe species vary in their host specificity. Amyema miquelii is usually parasitic on eucalypts (Cormybia & Eucalyptus) and is only rarely found on other genera. Within the eucalypts, it shows a strong preference for box-barked species (such as Eucalyptus microcarpa, grey box, in the Adelaide area), and some smooth-barked gums that are related to the boxes such as E. fasciculosa (pink gum) and E. leucoxylon (SA blue gum), as well as number of mallees mainly from the red mallee group. Its drooping, falcate leaves mimic those of its eucalypt hosts.

Amyema miquelii habit (left, photo: J.G. Conran) and flowers, buds and foliage (right, photo: P.J.Lang).

Amyema pendula is the most similar species to A. miquelii and is sometimes confused with it. Its leaves are of a similar shape but tend to have more obvious parallel venation and a somewhat rusty tomentum. It is most clearly distinguished by the flower clusters which have the middle flower sessile (lacking a stalk). There is very little overlap with A. miquelii in its host preferences.  Amyema pendulum is most commonly found on the stringybarks (Eucalyptus arenacea, E. baxteri, E. obliqua), and on selected gum species (E. viminalis, E. camaldulensis, E. ovata), as well as Blackwood Wattle (Acacia melanoxylon).

Amyema pendula flowers (left, photo: P.J.Lang), Mistletoe bird (right, photo: Duncan McCaskill, CC BY 3.0, cropped).

Mistletoes fruit form a principal component of the diet of the mistletoe bird (Dicaeum hirundinaceum), and in turn the bird has evolved to become a major disperser of mistletoe. They have a simple gut that can obtain sugars from the mistletoe fruit and pass it rapidly, avoiding damage to the embryo and leaving the sticky coating relatively intact. Furthermore their specialised perching behaviour helps position the defecated seeds on the host plant branches. Mistletoe birds are widespread across mainland Australia but absent on Kangaroo Island which may account for the lack of mistletoes species there.

Contributed by State Herbarium botanist Peter Lang

Plant of the Month: Feb. 2018

Olearia arckaringensis. Photo: P.J. Lang

A few months ago, State Herbarium botanist Peter Lang and SA Seed Conservation Centre‘s Dan Duval, were part of a field trip to Arckaringa Station.  One of the main aims of the trip was to survey populations of Olearia arckaringensis P.J.Lang, the State Herbarium of South Australia‘s Plant of the Month for February 2018.

Olearia arckaringensis, flower. Photo: A.C. Robinson.

The plant was first discovered in 2000 in gullies of breakaways in an isolated pocket of Arckaringa Station by DEWNR scientists Rob Brandle and Peter Lang. The daisy was recognised to be a new species and described in 2008 by Peter in the Journal of the Adelaide Botanic Gardens (895kb PDF). A further two populations were found in 2011 along the same breakaway system on the neighbouring property, Evelyn Downs. In 2016, O. arckaringensis was listed as Endangered under the federal EPBC Act (80kb PDF).

The recent survey discovered several new population of the species. The search took more than 100 hours and covered more than 100 km of breakaway country. The survey team counted and mapped well over 2000 Arckaringa daisy plants and confirmed that the species is rare with quite specific habitat requirements. It was mainly restricted to breakaway sites that had a softer more powdery underlying substrate and were situated in less exposed areas.

Voucher specimens of Olearia arckaringensis and other plants were collected for the State Herbarium and the Seed Conservation Centre. Such collections are vital to build plant knowledge and improve scientists’ ability to accurately describe and identify different species, whilst the stored seeds are a valuable insure against species extinction.

Olearia arckaringensis, old shrub with woody base. Photo: R. Brandle.

The plant is a small, compact perennial shrub, usually to around 30 cm tall, with grey-green leaves and light violet-lavender flowers (occasionally white) borne on long stalks. It rapidly develops a thick woody base from which it can regrow.

More information can be found in DEWNR’s newsletter The Weekly and SA Arid Land’s news release.

Olearia arckaringensis, plant in typical habitat. Photo: SA Seed Conservation Centre.