Tuesday, 18 November 2014

Cultivating Cancer Weed

For someone who loves to tell stories about plants that change the world for the better - Cinchona (quinine), Salix (asprin),  Hevea (rubber) and of course Coffea (ahhhh) - you think I'd be thrilled to discover that active chemical in the gel I smeared over my face to fix some skin blemishes was discovered in a plant.

Instead I started to doubt its efficacy. Was Picato really something to cure my latent skin cancers or was this something just to make me feel better? But then I thought about quinine and asprins, and decided it was a good thing as long as it was well tested and the extract was carefully measured. Not for me a tea made of some local weed with the hope that it might contain just the Goldilocks amount of an elixir. I don't want to be poisoned, misled or conned. And thanks to an Australian scientist, Professor Jim Aylward, and his mother, that doesn't have to be the case.

But first let's look at the plant in question, Euphorbia peplus. It's a small herb native to northern Africa, Europe and western Asia but now naturalised widely around the world, including much of southern and eastern Australia, and doing quite nicely in my backyard. It arrived in Australia shortly after European settlement and has become a common weed of gardens, paths and crops. Although well established it is generally not an aggressive invasive, except in few localised areas (e.g. it is listed as one of top 10 coastal weeds of concern in southern Western Australia).

The plant is soft and bright green, up to about 20 cm tall, with oval or spade-shaped leaves and umbrella-like clusters of green flowers or fruits at the top. The stems are usually reddish at the base. I'm sure you've pulled them out of your brick work or path at some time.

Common names include Petty Spurge or along with lots of other euphorbs, Milk Weed. It's even called by some, Cancer Weed - in a curative rather than causative sense I think - or Radium Weed. I'm presuming 'radium' again refers to its powers of good, rather than evil.

I should point out here that the plant is poisonous to us, and to many animals, and should not be ingested. Although unspecified mild doses have been used as a laxative you might keep in mind that seventeenth century herbalist Nicholas Culpeper described its action as 'working violently by vomit and stool'.  And as with most euphorbs, skin contact with the milky sap can cause dermatitis.

Ironically, or not, it is the sap that has been used for centuries to cure skin problems, particularly warts. There are plenty of reports of people using sap direct from the stem to fix all kinds of blemishes and more serious ailments, and many of us have dobbed a dab of white latex from this plant onto a wart just to see what happens. Although far more expensive, I prefer and would always recommend clinically tested and precise dosages for the face.

Back to our Australian scientist, Professor Aylward. In a radio interview in 2009, he said his mother cajoled him into studying the properties of this plant after she found it successful home remedy for treating sunspots. That was in 1997 when Aylward and his team of Queensland scientists discovered and isolated the active compound in Euphorbia peplus.

Named ingenol mebute, this chemical kills rapidly dividing and growing cells, of the kind you find in a sun spot or potential cancerous cluster.

By 2009 clinical trials were in place and in 2013 the product was released for general use in the form of three tiny tubes of gel to be applied one each day for three days. After fifteen days of ruddy complexion your skin becomes blotch and cancer free, at least for a while.

Well, I did it and it seemed to work just fine. In the backyard the Euphorbia peplus thrives, no matter how many times I rip it from the garden. Presumably its toxic sap wards off other predators, and the ability to produce these flowers and fruits within weeks of germinating must help.

Images: The shots of Euphorbia peplus are all taken in my backyard, the tiny tube of Picato gel in my kitchen. The last two pictures may help you work out whether it is the paired leaves or the tucked and pleated fruits that inspired the species name, a reference to the simple peplos garment worn by women in Ancient Greece.

Tuesday, 11 November 2014

Better to have foraged for Fairy Lanterns and failed…

I gather the thrill of shopping is as much about the planning, the anticipation and the hunt, as it is about the purchase. Still I suspect without an occasional purchase it might become a little anticlimactic.

Plant foraging is a bit similar, particularly if you are looking for native ground orchids. On Melbourne Cup weekend last year, Lynda and I took up the ultimate botanical challenge, a native under-the-ground plant closely related to orchids.

We were in the Otway Range, rummaging around one of only six known localities for Fairy Lanterns, Thismia rodwayi, in Victoria. And we were unsuccessful. Not a tentacle to be seen. Perhaps we were in the wrong place at the wrong time. Or the right place at the wrong time. And so on. It’s not easy to find something that lives its entire life underneath the leaf litter.

If we had found it, it would have looked like this (each lantern-like flower is about 3 cm long):

We seem to have only one species of Thismia in Victoria, but when a plant is this hard to locate and study, who knows? Ten years ago a new species was discovered in Morton National Park, near Bundanoon in New South Wales. It was only the second report of Thismia from New South Wales.

Local naturalist Pat Jordan was part of a community fungal survey, Fungimap, in her local National Park. She thought the flower was a fungus and sent it our fungal expert here in Royal Botanic Gardens Melbourne, Dr Tom May. Recognising it as a Thismia, Tom showed it to visiting botanist Kevin Thiele, based in East Gippsland where the genus is relatively well known. He declared it a new species.

Thismia grows almost entirely underground and produces no leaves. It bears a single red to orange tubular flower, with a mitre-like cap and tentacles just emerging into the leaf litter. The whole plant is about 3 cm long. And only a few people have ever seen them in the field in Australia.

There are 30 known species of Fairy Lantern, mostly in South-east Asia and South America. Before this species was discovered there were only two known from Australia – one in Cape York, the other scattered around southern Australia.

Fairy Lanterns are closely related to orchids. The huge orchid family, Orchidaceae, includes over 20,000 species, of which only two grow underground. They both belong to the genus Rhizanthella, first discovered in 1928 near Corrigin in south-western Western Australia, and so far unknown outside Australia.

Fairy Lanterns and these orchids rely on fungi growing on the roots to get all their food and nutrients – they are mostly underground and don’t have any green parts so they can’t photosynthesise their own sugars and energy.

How are they discovered? Usually by accident. But also after very careful and intensive searching of likely areas.

The species are distinguished from one another mostly on the type of tentacles on the mitre-like cap. The Bundanoon species has been named clavarioides due to the resemblance of these tentacles to the ‘coral fungus’ Clavaria. When Pat Jordan first saw the tentacles of these flowers she thought they were a coral fungus.

The complete distribution of such underground plants is not the only mysterious thing about them. So too is their method of pollination. The flowers of fairy lanterns and underground orchids appear to rely on tiny flies, ants and termites, or other insects that flit about in the litter layer. Yet many ants—the most common visitors to the Western Australian underground orchid—secrete a potent antibiotic called metapleurin that should kill pollen. How the orchid overcomes this, we don’t know.

In the case of fairy lanterns the flowers are designed like yabby traps. Kevin Thiele postulates that insects can escape the trap but only after squeezing past a gland (that may secret glue) and the pollen sacs. The fruit of all these underground plants is probably dispersed by small marsupials searching for underground ‘truffle-like’ fungi such as truffles, but again we can’t be sure.

So plenty to discover about the Fairy Lanterns, as well as where they live. On balance I think its best I didn’t find one on my first search. Like travel, rather than shopping perhaps, it’s good to miss a few things so that you still have things to plan, anticipate and hunt.

And I'm well used to this kind of unfulfilled potential from above-ground orchid hunting. I saw a few orchids in flower over the Melbourne Cup weekend, but not great display. Although at least with above-ground orchids you often find a leaf, or a spent flower. These two are from Anglesea, on the return trip from the Otway Range. They will be readily recognisable to those with the bug.

Images: The Thismia picture was taken by Neville Walsh, and is from the Otway Range. Note also that some of the information in this post is taken from a story I wrote for Nature Australia magazine in 2004 (not available on-line).

Tuesday, 4 November 2014

Floral headbangers, plants that like metal

Some plants need extra metals in the soil to survive. They are called, quite logically, metallophytes. Others can take or leave the metals. and they are called, more dubiously, pseudometallophytes. Either way the plant excludes or accumulates the metal, although mostly the pseduometallophytes exclude and the metallophytes accumulate.

While I was in the UK earlier this year I took an overnight trip to Durham. I was there to help with a freshwater algal identification course but along the way I saw a whole lot of metallophytes and pseudometallophytes in the tailings from the mining of lead and other minerals in the West Pennines.

The metal tolerant plants are spread across 34 or so families but Brassicaceae, the cabbage family, is commonly represented. This Arabidopsis haleri was the most commonly encountered Brassicaceae I noticed in the West Pennines.

Like plants living in very salty soils, some (pseudo)metallophytes excrete the metal through glands and hairs. At least some forms of the pansy illustrated at the top of this post, Viola tricolor, are known to to accumulate metals in their hairs and then shed them. So they kind of accumulate then exclude.

These are three other pretty flowers present in the metal rich meadows: the Eyebright (Euphrasia officinalis), the Common Bird's-foot Trefoil (Lotus corniculatus) and what I think is the White Common Spotted Orchid (Dacylorhiza fuchsii subspecies okelleyi). I don't know whether thery accumulated, excluded or both, or how. I also couldn't get a clear answer on whether these species were all native to what may have been naturally mildly metal-rich soils or whether they colonised during and after the mining.

Elsewhere (pseudo)metallphytes are being used to not only restore vegetation after mining, such as Pig Face (Carpobrotus rossii) to clean up cadmium in Australia, but sometimes to prospect for metals like gold.

One day we might even be able to harvest rather than mine our metals. Earlier this year New Scientist journalist Katia Moskvitch reported on attempts to extend decontamination of a nickel-rich site to extracting the metal from a species of Alyssum (a Brassicaceae). The plants concentrate the metal in their leaves, which are harvested and burnt, with the ash then processed in a smelter or refinery.

Nickel yields of more than 100 kilograms per hectare are possible with the right fertilisers and herbicides (the latter to kill off competing plants and something that would need to be carefully monitored from an environmental perspective you would imagine). Alan Baker, a leader in this study, is now based at the School of Botany, University of Melbourne.

As for metal that doesn't end up in a plant, well in the West Pennines anything mobile finds its way into this river which locals proclaim proudly to be their one and only pea-green river. No where else, I was told, would you find a river so green.

Postscript: From Facebook:

Jim Croft Symplocos accumulates so much aluminium, leaves of herbarium specimens can be bright yellow.

Tuesday, 28 October 2014

Western Australian Christmas Tree not so sweet in the east

Two months ago I was in the Australian Garden at Royal Botanic Gardens Cranbourne - part of mighty Royal Botanic Gardens Melbourne empire - with Steve Hopper and his wife Chris. Steve is a Professor at the University of Western Australia and previously Director of Perth's Kings Park and Botanic Gardens as well as that little old garden in London, Royal Botanic Gardens Kew.

So he knows something about plants and in particular the plants of Western Australia. I was keen to show him Howson Hill, part of the second stage of the Australian Garden. Steve had been there for the opening of Stage One but hadn't seen the recent developments.

He was impressed by it all but enjoyed seeing Western Australian plants thriving on Howson Hill, including some he had named himself. One he certainly hadn't named, but I wanted him to see was our Western Australian Christmas Tree, Nuytsia floribunda, the largest (semi)parasitic plant on Earth.

Nuytsia in in the mistletoe family, Loranthaceae, and has only one species which occurs naturally in the south-eastern corner of Western Australia. It gets to 10 metres tall, and is covered in yellowy orange flowers around Christmas time.

This is one amazing plant. It's a semi-parasite (that is, it also has green leaves and does some of its own food production) that connects to the roots of any nearby plant. It's not choosy - annuals or perennials, grasses or shrubs, plants or powerlines... To get inside the root of the plant it cuts half way through and then penetrate into the food and water transport system within. Steve said that in Western Australia Nuytsia has been known to black-out houses when it cuts through an underground power-line instead of a root.

This Western Australian Christmas Tree at Cranbourne is one of the first plantings on the site, moved there not long after it was purchased, in the 1970s. Thanks to the horticultural expertise of Warren Worboys, Curator of Horticulture, seedlings were germinated and attached to willing hosts. Three were planted out at Cranbourne, only one surviving to maturity.

There are very few examples of this species growing in cultivation, particularly in the east. We promote ours as the most southerly specimen in the world, and sometimes as the most easterly.  Steve Hopper reminded me that one of the early Directors in Sydney, grew it to at least cotyledon stage (that is, with seed leaves), discovering to his surprise that it had three or four of the damn things. It's a 'dicotyledon' which tells you how many cotyledons you should expect (usually) - two!

On our visit, in late August it was exuding this transparent to amber coloured resin. With a texture, and as it turns out taste, like silicon sealant, there were half a dozen 3-5 cm in diameter blobs (about the size of a fat cicada) hanging from the trunk. Steve was familiar with them from Western Australia and said the the Noongar, the Aboriginal people living near Perth, ate them as a sweet.

As we tasted a small sample, we regaled each other (and Chris) with stories of how many bushfoods have to be pretreated in some way to remove poisons. In a botanic garden one must also have the permission of someone like the Director and Chief Executive to sample and eat any plant material. Lucky I was on hand.

As you can perhaps surmise from this picture of Steve sampling a fragment, it wasn't sweet. In fact it wasn't anything. Just like I imagine silicon sealant would taste without the drying spirit added to it. We didn't die or fall ill. We just didn't want to eat any more. Checking later on the internet I find it reported as a 'sweet gum', eaten raw by people indigenous to its natural area.

Clearly we need some help from Aboriginal people who know more about this plant. Of course it may be that while proud of our achievement, growing Nuytsia at its most southerly and easterly limit isn't good for the production a sweet gum.

Tuesday, 21 October 2014

With Don Watson in search of lost Mallee (Plant Portrait X*)

I was born in the Nhill Hospital but because my parents moved on when I was only two, I can't really say I lived in any remembered way in Nhill.

Still, I experienced Victoria's Mallee as a child through regular visits to my cousins' house, a few miles (as it was then) out of Hopetoun. After my father died when I was six, and we had moved to Euroa via Wangaratta, my two younger brothers and I spent even more time there, enjoying an odd mix of dusty, anarchic adventure and access to a vast library of mostly humorous English writing, all in paperbacks.

Don Watson also spent time in the mallee, but mostly as a contemplative adult, long after his childhood in Gippsland. I've just finished reading his The Bush: Travels in the Heart of Australia and there is plenty in the book that resonates and causes me to reminisce.

Book Cover: The Bush

Watson's family, like many who farm, say they come from The Bush. I've always said I come The Country. My rural life was in country towns, the son of teachers. Don Watson's was from a farm, or two. In his book Watson travels from his childhood to his penultimate home in Mount Macedon (he has recently moved back to the city), via much of eastern Australia.

Watson's description of the Mallee, in particular, rings true. The mice plagues, I remember well. He mentions tails dangling from cracks in the ceiling (one of the more savoury stories amid the mass slaughter of these rodents). I remember lying awake at night waiting for them to drop to the floor and during the day lifting up sheets of corrugated iron to shriek in horror/excitement at the seething mass of whiskers and tails beneath.

And Don Watson marvels, as he should, at the plans of the 80-year old Bosisto company to increase their eucalypt oil production in the Bendigo whipstick, just east of the Mallee, to not only out-compete China (today's leading producer of eucalypt oil) but to one day produce a substitute to petroleum. (Bosisto's fascinating story was also featured on a recent episode of ABC's Landline.)

Mostly, though, the Mallee is and was about wheat and sky. One of my stronger childhood memories is waiting on the station at Sea Lake, with no other soul around that I remember, watching the sun rise and then the dust from my uncle's car grow closer, all in relative silence before I was enveloped into the noise of the Hopetoun household.

I also remember sitting on the veranda of a house not far from my cousin's place, with farm junk scattered around, watching a sunset I think. It's often about watching, and about the softer edges of the day, when it's not so hot and not so harsh.

In the early years I would be viewing the Mallee from a caravan placed somewhat arbitrarily in the one or two hectare, square property plonked in the middle of the wheat fields (not, I should add, in the middle of this road somewhere in Victoria - this is clearly just a toilet stop for me). My uncle was a lawyer with offices in various of the local towns. He had a huge, and to his children greatly wearing, knack for funny stories and he liked to grow Australian plants in a fairly haphazard but courageous style,

Not every one likes the mallee. Watson says that the first Director of Melbourne's Botanic Gardens, Ferdinand von Mueller, bypassed it on his way to collect plants further north in Australia.

The book is about much more than the Mallee. It reaches from the soggy forests of Gippsland to the lonely interior of the continent. From Aboriginal care to European distrust. I like that Don Watson sees his later search for imperfections (in life and language we presume) as coming from being taught to 'spot the thistle in the daffodils'. This kind of upbringing, he muses, make you see faults before loveliness.

It's a meandering story, at times as tangled as the weedy scrub European settlers have allowed to replace the bush they cleared. That's not a bad thing and I have a tendency to stray a little myself. Here, for example, is my uncle's Valiant in which I later learnt to drive (in this picture I am a small boy talking to my mother in the back seat, while my father I suspect is taking the picture). It is parked next to what I presume is Lake Lascelles, just out of Hopetoun, on which my cousins sailed every now and then, when it filled. Or perhaps it is Lake Albacutya further to the west. As Watson notes, like Lake Eyre, these Mallee lakes are remnants of the long departed inland sea.

As you'd expect, Watson's book has some lovely writing, with sparkling sentences and sentiments such as this, describing those in search of Red Ceders in the Big Scrub in the mid-nineteenth century: "We don't know how far they regressed, if at all, but if they are indeed among the progenitors of the national character and values, it might be a calculation worth making."

One of the best is almost lost in a bracketed aside after a story of a boy's lie about checking a windmill leading to the death of a hundred cattle: "Along with birdsong and room to roam, it is one of the privileges of a country childhood to live in permanent fear of a biblical drubbing should one neglect to shut a gate or turn off a tap". That same privilege seeped through to us townies who schooled and played with kids from the farms.

Notes: After writing this I interviewed Don Watson for the radio version of Talking Plants, to run over the Christmas break on ABC Radio National. Turns out he's a keen gardener and, as you'd expect, able to link gardening and plants to the bigger questions in life. (You'll note the images here contain few attractive plants, reflecting accurately my memories of the Mallee.)

Tuesday, 14 October 2014

No great wine escape

Botanical colleague Neville Walsh was wondering, aloud, why you don't see grape vines taking over the Victorian bush. They grow well in many parts of the State, they produce plenty of fruit, and the seed-containing pomice from wine and juice making is often discarded outdoors. Yet there are only a handful of reports of its escape into natural vegetation.

Neville presumed, aloud, that the seed was most likely infertile. My extensive sleuthing on the internet supports this presumption, sort of. Growing grapes deliberately from seed it not easy. It can, according to one experienced grower, take up to three years. Firstly, only a small number of seeds will germinate. It may be that they are mostly infertile but also because they require 'stratification'.

That is the seeds need to be pretreated in some way before they germinate. Only by subjecting them to few months of cold temperatures to trigger the plant to force it's way through the tough seed coat.

According to this same source, Danie, once extracted from the fruit pulp, the seed need two to three months at just above freezing (1-3 degrees C). This alone would make most of Australia unsuitable for colonisation by a rogue grape.

Seed will still take a few weeks to germinate, and there are reports of it taking up to eight. Even after stratification the strike rate is low.

Other people simply recommend sowing the seed and then waiting for three months, presumably in places where temperatures drop a little and help the seed break its dormancy.

This is presumably why Vitus vinifera, the wine grape, is only 'sparingly naturalised' in Victoria. I notice that it's described as full-on naturalised (i.e. established and spreading in the bush) in Western Australia, South Australia and New South Wales (and 'doubtfully naturalised' in Australian Capital Territory).

That summary may over inflate the real situation given that in New South Wales, for example, the distribution based on vouchered (herbarium) records is 'occasionally naturalised' and there are only three records on the PlantBank database. How close these are to domesticated vines I don't know but the dots seem to be in established wine growing regions (e.g. Hunter Valley).

There are more dots (on the map) in Western Australia but mostly hugging around Perth with just a few in the Margaret River area. In South Australia there are 18 records, scattered around the south-west wine growing areas.

I don't get the impression it's a sleeper weed, with the potential to break out and rampage through our native vegetation. But if the climate changes to its advantage and we are careless in where we toss our pomice, who knows.

Images: The vineyard at the top is beautiful Tarrawarra in the Yarra Valley, where I saw no evidence of escaping wine vines. The other picture is of a single plant, one of the oldest and biggest in the world, growing inside at Hampton Court Palace and therefore unlikely to escape.

Tuesday, 7 October 2014

Close encounters with the Teddybear Cholla

The sign was clear. Don't touch. Don't even think about touching the Cylindropuntia bigelovii, even though its common name is the Teddybear Cholla (pronounced choy-yah).

So I picked up a small piece. Swore. Flicked it onto my foot where it attached itself securely to the front of my shoe. I eventually managed to scrape it off on a rock and then break the remaining spines back to the rubber in my shoe. This was two weeks ago, while in the Joshua Tree National Park south-east of Los Angeles. The spiny remnants reside in my shoe still today.

Back in the desert as temperatures hit 96 degrees F (around 36 degrees C) in what is quite appropriately called the Cactus Garden, Lynda mumbled something about signs and kids. I licked my wounds.

The Teddybear Cholla is by far the most common species of cactus in the park and pretty successful at getting around. It's a close relative of the prickly pear and in fact used to be included in the same genus, Opuntia. The most obvious difference is that the chollas (there are others in this group) have cylindrical stems (i.e. the green blades that make up most cacti) while the prickly pears are flattened ones.

The spines are also different, as I experienced. Many opuntias (as I can also attest) have clumps of tiny 'glochids' which look innocuous but persist and irritate long after any contact with the cactus. The chollas have pretty obviously aggressive spines and you'd be an idiot to even touch them.

The Teddybear Cholla is also called the Jumping Cactus due to its propensity to find its way from the ground to some part of our body. It can seem at times like it jumps at you. All these detached bits and pieces readily root and settle in as new plants, sometimes after being transported rather long distances (e.g. to Australia; although I should say that personally I may have carried fragments of spines, but not flesh of the cactus).

I gather the easiest way to remove the reverse-barbed spine from your skin is to use a comb and to 'quickly jerk it away'. I wasn't carrying a comb and in any case, due to the force required I gather there is also a risk it flies straight into your companion, making a fresh connection.

A mature specimen is about one to two metres tall, with the base becoming trunk like with age as lower branches die and fall off. The spines cover pretty much the entire surface of the plant, which must make it difficult for sunlight to reach the green photosynthetic tissue. Presumably protection from desiccation and predation are more important.

Young spines are yellow. Old ones black. Yellow-green flowers appear in spring with the fruits, as illustrated here from mid-autumn, mostly without fertile seeds. It does nicely without resorting to sexual reproduction it seems. In fact according to the Arizona-Sonora Desert Museum, many plants have three rather than two sets of chromosomes, and are completely sterile. These sterile plants can still cover up to two square miles desert excluding nearly all other plants.

This species is common in the Mohave Desert and hotter parts of the Sonoran Desert, both of which intersect in the Joshua Tree National Park. And I can't really post about the Joshua Tree National Park without a picture of the striking Joshua Tree (Yucca brevifolia) so here it is!

Notes: Thanks Lynda for the final picture, and yes I lied when I said my last post was the final one from my US holiday. This one, almost certainly, is. 

Tuesday, 30 September 2014

It's tough at the top of the world's tallest trees

This is the second (and last) of my holiday posts from North America, in this case researched a little before I left Australia. It's a long one, pictorially, due to the elongated plant subject. I've traveled across the country (by plane), from giant topiary in New York last week to giant trees in California today. From the ridiculous to the sublime.

Back in 2005 when I wrote an article for Nature Australia magazine called 'Size matters', I reported that the world’s tallest plant was a 112.7-metre-high Coast Redwood growing in Humboldt Redwoods National Park, California. I think it still is the tallest but presumably plus or minus a metre or two now. It grows a few hundred kilometres north of where I saw and photographed this Giant Redwood.

Just for the botanical record, the Coast (or Californian) Redwood is Sequoia sempervirens, the only species in this genus. A closely related and equally 'big tree' is called the Giant Redwood, Sequiadendron giganteum, and it is also the only species in its genus.

Despite its common and botanical names, the Giant Redwood doesn't grow quite as tall as the Coast Redwood, but it achieves bigger bulk - that is, the volume of its trunk is the largest in the world (the Montezuma Cypress, Taxodium mucronutum, in Mexico has the largest girth - over 15 metres in diameter). Both Redwood species frequently top 100 metres in height but the tallest conifer ever recorded was a 126-metre Douglas Fir, Pseudotsuga menziesii.

All these conifers are clearly big trees. Flowering trees, like our gums, also grow tall of course. Although there are claims of Mountain Ashes (Eucalyptus regnans) in southern Australia being over 120 metres, the tallest ever measured officially was 107 metres. Today the tallest living specimen is I think still a 97 m tree called ‘Icarus Dream’ in the Styx Valley in Tasmania. It's quite possible this tree will reach 100 m over the next few decades.

But don't expect it, or even the Coast Redwood, to ever get to 130 metres. As I reported back in 2005, what limits their size is a plumbing problem: how do you get water from the ground to a leaf fluttering 100 or so metres above?

George Koch from Northern Arizona University, and his associates, reckon we'll never see a redwood over 130 meteres tall. They climbed the world’s tallest trees to measure water potential and photosynthesis in the highest branches, followed by more detailed analysis of leaves transported back to the laboratory. Water is drawn up the tree (what we call transpiration) in a continuous column as it evaporates from leaves into the atmosphere. They found that gravity starts to win out against water cohesion at around 110 metres.

It turns out the leaves most distant from the base of a gigantic Redwood such as this one are under extreme water stress, and their small size and low photosynthetic rates may be due to the plant closing some of its breathing pores (stomata). This would not only retain precious water, but also slow down the rate of water transport through the plant, reducing the possibility of deadly air bubbles being formed—a break in the water chain would be permanent and mean death for a lofty limb.

They also found that to keep one of these big trees alive and transpiring healthily, the surrounding forest must remain intact to maintain high moisture levels and buffer the trees against storm damage. So if we want to see big trees in California, or in Australia, look after the forests that surround them. The recent drought in California is putting some of these big trees under additional stress, so doing what we can to reduce the severity and impact of climate change will also help our botanical giants survive.

Images: All from Mariposa Grove, at the southern end of Yosemite, taken last Wednesday (I'm now back on Melbourne). Lynda very kindly photographed the top picture.

Tuesday, 23 September 2014

Toy Topiary keeping an eye on the Big Apple

Last week I visited New York's (rather than Malvern East's) Central Park, which was as incongruous and inviting as I expected, although more so 70 floors up from the Rockefeller Centre. Instead of showing you lots of photographs of that striking green edge to New York's skyscrapers I give you this floral horse-dinosaur, by Jeff Koons.

Slit-Rocker has grown in Avignon, Versailles and Basil. Since June it has bloomed behind Paul Manship's gold Prometheus sculpture in front of the GE Building at 30 Rockefeller Place (and I can't help but hum the theme song from the TV show 30 Rock every time I type or say that).

Apparently there are 50,000 petunias, geraniums, begonias, fuchsias, impatiens and marigolds covering this 11 metre tall fusion of half a toy pony head and half a toy dinasaur head. Although watered by an internal irrigation system Koons says one of the things he is intrigued by is giving up control and seeing what happens. 'It's in nature's hands' he says.

In case you are interested, this is part of the infrastructure behind the flowers, in a photograph I took a few days later, after all the flowers had been removed.

According to Plantcurator.com, to keep one of his previous flora sculptures (Puppy) alive, if not kicking, a gardener attended to it weekly removing weeds, replacing weak plants and giving extra water if needed.

These nature's gardeners may be tending the plants, or perhaps starting its deconstruction as the square is readied for its next big plant exhibit, the annual Christmas Tree. There is also a Koons' retrospective at the Whitney Museum of American Art, running until mid-October, but I was museumed out after visiting the Met, the Guggenheim and MOMA.

Given there is not a lot more I can say about this without a) sounding pretentious, b) giving away my lack of knowledge of modern art and artists or c) doing more research, let me finish with Central Park, from 30 Rockefeller Plaza. The border of the buildings and park is Central Park West, a street Bob Carr in his Diary of a Foreign Minister calls the world's most beautiful (and anyone who has read the book, or knows Bob, will be aware he is not a man prone to hyperbole or hubris).

Or, you can finish with a lovely plate featuring Koons' floral half pony, half dinasaur. You choose...

Tuesday, 16 September 2014

Careful, they might hear you

On my first visit to China, ten years ago, to the Xishuangbanna Tropical Botanical Garden, I was intrigued by this plant Codariocalyx motorius. According to my Chinese colleagues it responded to singing by wiggling its stipules, small flaps at the base of its leaves.

As I mentioned in a post a few years ago, the plant failed to perform. It may have been our fault. Rather than sing, a mobile phone ring tone was used to entice the Dancing Plant, as it was called, to dance. I assumed it was probably the vibrations caused by particular noises that caused the response, when and if it did respond.

Now I can report that plants can 'hear' insects munching on their leaves. This discovery by scientists at Missouri University comes close on the heals of a revival in interest in plants communicating with one another (extending the sharing of genetic material). The distinction between plants and animals becomes increasingly blurry.

This cabbage butterfly caterpillar munches on an Arabidopsis leaf adjacent to  a leaf where a piece of reflective tape bounces back a laser beam used to detect the vibrations created by its chewing. Roger Meissen/Bond LSC

The plant with ears is the popular experimental mustard plant or cress, Arabidopsis, and the noisy eater the caterpillar of the Cabbage Butterfly. Vibrations from the caterpillar's eating travel through the leaf and stems, triggering chemical defenses by the plant. Wind and other vibrations applied to the plant don't cause any reaction - it's all to do the frequency of the caterpillar's crunch.

Whether you could really describe this as the plant hearing noise is of course a moot point. Although sounds are usually defined as vibrations traveling through air and received (heard) by something else. That fits pretty well what is going on in the mustard-caterpillar interaction.

As you'd expect, these sounds are very quiet. Microphones can't be used due to the small size of the leaves and the caterpillar's mouth, but a piece of reflective tape nearby (see attached to the leaf next to the white caterpillar above) reflects a laser beam which gets disturbed by the (minutely) noisy eating. This response can be amplified to a speaker so that we can hear the caterpillar's crunching.

In response to this quiet racket, the plant produces a number of defensive chemicals, one of which is called glucosinolate. Glucosinolate makes mustards spicy, may cure cancer in humans, gives red wine its colour and making chocolate healthy. For a caterpillar, however, it is repellent.

Playing the chewing noise back to plants caused higher levels of glucosinolate to be produced. Other sounds and frequencies had no effect so it isn't just the leaf shaking about that causes this response. 

Returning to my Dancing Plant, the researchers say that “The field is somewhat haunted by its history of playing music to plants . That sort of stimulus is so divorced from the natural ecology of plants that it’s very difficult to interpret any plant responses.” 

I suspect they are referring to people suggesting that playing music to plants makes them 'happy' and grow better, as featured in the book, The Secret Life of Plants. When such responses are detected (not often in experimental situations) it is most usually attributed to increased carbon dioxide from humans exhaling nearby or perhaps air movement encouraging greater gas exchange into and out of the leaf.

For a more learned summary of research into what are more properly called 'acoustic emissions' from plants, see Monica Gagliano's (from the University of Western Australia) 2012 summary in Behavioral Ecology. Gagliano concludes that more and more we find that plants 'highly sensitive organisms that perceive, assess, interact, and even facilitate each other by actively acquiring information from their environment'. She says they effectively 'cry for help' when they respond like the cress does to the caterpillar and that there is likely to be more to discover in this controversial but fascinating area of plant biology.

Next up for the Missouri team is to find out whether other plants respond in similar ways and what it is precisely in the vibration, or sound, that triggers the plant response. It's nice to think that plants might do more than dance in response to niggling noises.

Notes: the image of the caterpillar on the Arabidopsis comes from the Decoding Science website, and the idea for the story from colleague Peter Symes.

Tuesday, 9 September 2014

Fungal farm to wormy wood: the ambrosia story

The original Wormy Chestnut was indeed a chestnut, scarred by worms. It was an American Chestnut, Castanea dentata, killed by chestnut blight then chewed by insects that left holes and discoloured the wood while they remained standing.

Because American Chestnut was almost wiped out by the early twentieth century blight, the wood became rare and valuable.

Australian Wormy Chestnut seems to be a mix of East Gippsland eucalypts, such as Eucalyptus obliqua, Eucalyptus sieberi and Eucalyptus fastigata. One of the companies selling it says it is "distressed by Mother Nature", which another company describes as the (attractive) ravages of "fire, ambrosia beetle, pin holes and squiggly worm marks".

The ambrosia beetle is kind of weevil. They are also called pin-hole borers, but not the ones responsible for the neatly drilled holes in old furniture (and the dust that they toss out of the hole). The ambrosia borers like 'green' wood, preferably freshly felled.

The beetle bores a hole into the wood to lay its eggs, and carries with it the spores of  the ambrosia fungus. The spores germinate, the fungus grows, the egg hatches, the larvae eat the fungus. The parent beetle often dies, conveniently, at the top of the tunnel, blocking it from predators and keeping the rain out.

By the time the wood is turned into flooring planks the beetle, it's larvae and the fungus are long gone. Or at least their remains are well dead. The fungus usually stains the wood, leaving a distinctive dark colouration, part of the attractiveness of the final wood product it seems.

representative image of taxa

The wonderfully named Austroplatypus incompertus (meaning something like the poorly-known southern flat-foot) likes trees burnt in bushfires, or similarly injured, and it produces 'extensive gallery systems in one plane only'. The plane, is horizontal, in a standing tree, meaning that the timber can easily fracture at an area of activity.

There is at least one other species of ambrosia beetle in these forests, the Mountain Pinhold Borer, Platypus subgranosus.  In case you are wondering, and I certainly was, the reason the platypus has the genus name Ornithorhynchus rather that Platypus is because this little fella, or at least one of its relatives, was named first.

But enough of beetles, this is a plant (and fungal, and algal...) blog! I bet you are wondering about the ambrosia fungus that colours up the Australian Wormy Chestnut wood so appealingly. There is a whole website devoted to the endearing relationship between beetle and fungus. And this (from the Ambrosia Symbiosis site) may, or may not be, the fungus...

The fungi associated with the ambrosia beetles are a mixed bag, and not all part of a single taxonomic group. This one is a Fusarium, a genus including lots of economically and environmentally important pathogens. There are also filament-forming yeasts and the helpfully named Ambrosiella.

Mostly the fungi can't survive without their ambrosia beetle overlords, but at least some of the Fusarium stock or crop (depending on your perspective, but do remember that fungi are more closely related to animals than to plants) seem to be able to fend for themselves if necessary.

Most or all of the fungi concerned have foregone sexual reproduction, apparently content with their life of coexistence with ambrosia beetle. Although it's not all peace and harmony. There is evidence of fungal rustling, with smaller beetles drilling holes near larger ones to save the bother of carrying around their own fungi.

So there you have it. A small glimpse into the murky world of the ambrosia symbiosis, as it's called. Beetles, fungi and dead trees combine to create an intriguing ecosystem that we slice up, polish and then walk on.

Image: The top picture is Oscar, a dog, doing tricks on the newly laid Australian Wormy Chestnut floor in the house of my friends Mal and Sandy. The annotated wood panel is from Triton International Woods and the image of the Austroplatypus is from Atlas of Living Australia (the species incompertus was included originally in the genus Platypus)