Today is National Tree Day, a community event designed to co-ordinate tree-planting programmes across Australia and raise awareness of the important role trees have in our environment.

In celebration of this event and as part of the Melbourne Design Festival (who sponsored the Melbourne Open House), the Melbourne Central Shopping Centre have commissioned famous French artist/botanist Patrick Blanc to create a Mur Végétale or “wall of plants” in Melbourne.

Patrick Blanc’s “Le Mur Végétale” at Melbourne Central.

Measuring a massive 40 square metres, this amazing vertical garden features a range of ferns and tropical species including African Violets (Saintpaulia) and bromeliads. The garden is mounted on the wall beside the historic Coop’s Shot Tower building under the huge glass dome at Melbourne Central.

Whilst Le Mur Végétale would be able to utilise some of the natural light in the shopping centre for photosynthesis, supplementary lighting has been provided to permit better plant growth and to highlight the artwork.

Living plants clean the air at Melbourne Central.

I really enjoy art like this. It’s detailed, its unique, it’s attractive and it’s eye-catching.

As I walked past the work today, I noticed many shoppers were stopping to admire Blanc’s living artpiece, which surely must have taken months of planning and execution.

Shoppers enjoying “Le Mur Végétale” at Melbourne Central.

Blanc has become famous the world over for his elaborate vertical gardens. The botanist cum vertical landscape designer is probably best recognised for his living wall on the Musée du Quai Branly in Paris, but has completed dozens of other projects internationally.

Le Mur Végétale is a three-part system consisting of a PVC layer, felt, and metal frame, providing a soil-free self-supporting system light enough to be hung on the wall and weighing less than 30 kilograms per square metre. Cuttings, seedlings and mature plants are then added to create the living vertical garden.

In a recent lecture given at the Federation Square and reported on the MIDF blog, Blanc explained that he’s first and foremost a botanist who approaches his work from a scientific perspective rather than an aesthetic one. The positioning of plants is as much about allowing each to receive an ideal amont of light with consideration given to the requirements of each species used, before any aesthetic considerations come into play.

Looking past “Le Mur Végétale” to the historic Coop’s Shot Tower (left)
and a young woman enjoys a rest beside the vertical garden.

Whilst these gardens technically have the capacity to continue growing in perpetuum, it is unclear whether the Melbourne Central installation will be a permanent fixture or not. The MIDF blog claims that the fixture will be permanent and I do hope they’re correct.

If true, there would certainly be a lot of ongoing work required to maintain this garden over an extended period, ensuring the survival and/or replacement of all the specimen plants periodically, and ensuring that the plants are fertilised sufficiently.

That said, Blanc’s artwork brings considerable environmental benefits. Aside from carbon assimilation, all of the water used in Le Mur Végétale is routinely recycled, having been sourced from the centre’s airconditioning units.

“Le Mur Végétale” is located adjacent to the historic Coop’s Shot Tower.

Regardless of the longevity of this particular work, it’s been great to see one of Blanc’s amazing vertical gardens here in Melbourne. It’s certainly added a unique talking point to the Melbourne Central Shopping Centre.

One of the delights of winter in Australia is the flowering of the wattle tree (Acacia). Whilst wattle pollen causes endless days of misery for certain hay fever sufferers*, the delightful yellow flowers of the wattle adds more than a touch of colour to a drab winter landscape and serves as a reminder that spring is on its way.

Acacia glandulicarpa.

This year I’ve been surprised to discover most species of Acacia blooming in mid-July. In fact, I even found one species of wattle flowering in early May! It does make me wonder if this is not a biological response to Climate Change, because such early flowering is very unusual.

Whatever the reason for the incorrect scheduling, it is nice to wander the suburbs and appreciate the diversity and colour of the many species of wattle flowering at present. Australia has 950 indigenous species of Acacia out of a total of 1200, the remainder being native to parts of Africa. It’s therefore no surprise to find a wide range of forms, flower colours, leaf shapes and growth habits amongst this diverse group of plants.

Most Australians are familiar with Acacia pycnantha or the “Golden Wattle” which is Australia’s official floral emblem, but I want to tell you about a few different species that I like.

The first is A. willdenowiana, or the “Grass Wattle”. The common name of this Western Australian species is derived from its form, which is that of a sprawling shrub.  Acacia willdenowiana seldom grows more than 60cm in height, but can spread to more than a metre and a half wide. Like many species of wattle, this one has no leaves. Rather it uses modified leaf-stalks (called phyllodes) to perform the normal functions of a leaf. Because of the sprawling habit of this species, the bright yellow ball flowers of this are nearly sitting on the ground. With its grass-like apparance and bright flowers, the Grass Wattle is quite a curiosity.

Acacia willdenowiana grows low to the ground.

Another species that I really like is A. longifolia, which grows up to 10 metres in height. Native to the eastern states, this species has long rod-shaped inflorescences of pale yellow flowers which almost smother the tree. The branches weep slightly to give the tree a pendulant appearance and the canopy is dense, making sure that the flower display can be seen from a far distance.

Acacia longifolia provides a vivid display.

Finally, I reckon A. flexifolia is worth a mention. I spotted this species in full bloom today and it looked amazing. This species is from central New South Wales, and grows to a height of 1.5 metres. It has upright stems which blow in the breeze. When covered in vivid yellow blooms this plant is very eye-catching. Unfortunately, I seldom see this species grown in gardens which is quite a shame.

Acacia flexifolia.

Of course an article about wattles shouldn’t go without mention of A. leprosa ‘Scarlet Blaze’, but I’ve already discussed that species’ unique red flowers in a previous blog post. Yes, wattles now come in red!

Acacia leprosa ‘Scarlet Blaze’ has unique red flowers.

As you’re walking to and from work or school in coming days, please take a moment to look at the wattle trees that are flowering in your neighbourhood. Pay special attention to the shape of the leaves and the colour and form of the flowers. If you do, you’ll no doubt be amazed at the sheer diversity that this species has. From small ground-covers to massive trees, this genus really has something for everyone.

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Useful Website: If you find wattles to be of interest, I highly recommend the World Wide Wattle website which is jam-packed with useful wattle info. The site has descriptions of every Australian Acacia species as well as photographs and links to other relevant plant databases.

*Fortunately, I don’t suffer from hay fever

I am fascinated by plants and I thoroughly enjoy photography. So what better way to combine these loves than with macro photography?

I am now reacquainting myself with the art after I purchased a macro lens last weekend – a Canon EFS 60mm f/2.8 Macro USM to be specific. And I am having a ball discovering the world at the micro level again.

For me, the macro lens is great because it allows me to capture the minute detail of plants that an ordinary 18-55mm lens is never going to capture. As someone who uses a microscope in his daily work, the macro lens is a nice ‘intermediate’ between the detail of a dissecting microscope and an ordinary camera lens.

Back in the days before digital photography, when I was a high school student, I used a Canon EOS 500N for all my photography. Of course I didn’t have the means to pay for a macro lens back then, so I settled for a Kenko tube extension kit. Sitting between the camera body and the standard 18-55mm lens, the effect was to increase the magnification capacity of the camera. It was a good substitute for a macro lens, and I used it frequently to capture the details of plants which was particularly useful during my horticultural studies at university.

Unfortunately, when I purchased my digital SLR, I discovered that the 350D used a slightly different lens attachment to the old camera and so my tube extension kit couldn’t be used any longer. Disappointed, I was determined that I’d buy a new macro lens. Eventually.

Having made the purchase, I am really happy with the Canon 60mm f/2.8 Macro. Such capacity for a high aperture really facilitates sharp photography at a level where the slightest shake will cause motion blur. Nevertheless, it decreases the depth-of-field considerably and so I am learning to adjust my photographic techniques to accommodate this.

The real challenge comes in using an appropriate aperture to increase the depth-of-field without reducing the light levels to make hand-held photography impossible. In some situations, a tripod just isn’t practical. Either way, it’s great fun and I am getting some great results.

Today I went to the Melbourne Conservatory in the Fitzroy Gardens to test out my macro photography. Of course the place was filled with other dSLR users trying to get photos, but I was able to focus on the small ferns, selaginellas and hydrangeas to get some special photos.

I’ll be working on my macro photographic technique in coming months, and of course will be posting to Flickr and Photologium.com.

Friends and family will be wondering what could possibly come next, after purchasing a macro and wide-angle lens? I reckon a fish-eye lens could be interesting….!

Picture details: 1. A marigold (Tagetes erecta cv.); 2. A Honey Bee pollinating a Sedum telephium ‘Autumn Joy’; 3. The flowers of a Hydrangea macrophylla.

I’d like to share with you an interesting new discovery in the world of plant science that follows on from my previous post about GM canola.

It relates very much to the current debate about genetic engineering; specifically one of the ways in which we plant scientists transform (or genetically engineer) plants.

The story goes back to 1977 when plant scientist Mary-Dell Chilton and colleagues at the University of Washington made a revolutionary discovery; that “genetic engineering” actually occurred in nature (contrary to popular belief).

More specifically, Chilton demonstrated that Agrobacterium tumefaciens caused Crown Gall Disease in plants by incorporating a part of its own DNA (called T-DNA) into the genome of the host plant via a Ti plasmid. This genetic change caused the infected plant to produce nutrients for the bacterium.

Agrobacterium tumefaciens infecting a plant cell. Click on image for more details. (© Nature Publishing Group)

Fast forward to 2007, and A. tumefaciens is frequently used in laboratories to genetically manipulate plants.

The virulence part of the bacteria’s Ti plasmid – the portion that causes the gall disease – is substituted by scientists for a desirable trait such as drought or herbicide resistance. The plant is then deliberately infected with the bacterium and a new gene is inserted into the plant.

Yet despite the frequent use of A. tumefaciens in laboratories, no-one actually understood how it was that the bacterium could get its DNA into the plant’s nucleus and not be detected by the plant’s defences.

Infecting Plants

The steps towards infection by Agrobacterium have been known for years.

The Agrobacterium comes into contact with a plant cell, and a single-stranded copy of T-DNA is passed into the cell, along with virulence (vir) proteins. The VirD2 protein is attached to one end of the T-DNA and assists its passage into the cell. The bacterium also inserts the VirE2 protein into the target cell, and with the assistance of karyopherin α the T-DNA is transferred into the plant’s nucleus (where its DNA is kept).

What wasn’t previously understood is how it was possible for the T-DNA to be carried into the nucleus past all the plant’s defences.

Solving the Mystery

Armin Djamei and Heribert Hirt at the University of Vienna have shown how the A. tumefaciens bacterium tricks the plant’s defence system and why the plant’s own VIP1 protein was the key to solving the mystery of T-DNA insertion.

When a plant is infected with A. tumefaciens, MAPK genes are activated. These cause the phosphorylation of VIP1 and other defence-related proteins, allowing them to enter the nucleus.

The VirE2 protein which the Agrobacterium injected into the plant cell simply allows the T-DNA to bind to the VIP1 protein, enabling those foreign genes to infiltrate the nucleus undetected. Once the genes are inside the nucleus, they are incorporated into the genome.

So in effect, the T-DNA enters the plant cell nucleus by utilising VIP1 as a Trojan Horse!

This finding is significant because Agrobacterium-mediated transformation is the most common method for producing GM plants, and therefore its comprehension is beneficial to plant science and plant pathology.

This also shows that with good research and patience, even the most elusive of biological processes can be understood in due time. I think these biological discoveries are fascinating as we learn more and more about the world around us.

Scientific References:

Binns, A.N. (2002) T-DNA of Agrobacterium tumefaciens: 25 years and counting. Trends in Plant Science 7 (5): 231-233

Chilton, M.D. et al. (1977) Stable incorporation of plasmid DNA into higher plant cells: the molecular basis of crown gall tumorigenesis. Cell 11: 263–271.

Djamei, A. et al. (2007) Trojan Horse strategy in Agrobacterium transformation: Abusing MAPK defence signalling. Science 318 (5849): 453-456

Snow, A. (2003) Genetic engineering: Unnatural selection. Nature 424: 619

Last week, the State Government of Victoria announced that the five-year moratorium on the cultivation of genetically-modified (GM) canola would be lifted in early 2008. New South Wales has also announced that it will lift its ban. South Australia is expected to follow soon whilst Tasmania wants to maintain its prohibition. The lifting of the moratorium is a highly controversial decision, but one that I welcome.

This story goes back to 2003 when the Commonwealth Government’s Office of the Gene Technology Regulator (OGTR) approved the cultivation of Bayer CropScience’s InVigor® and Monsanto’s Roundup Ready® herbicide-resistant canola (Brassica napus) for commercial oil production. In response, most Australian states (which have constitutional authority over agriculture) imposed 5-year moratoria on the basis that the economic and environmental risk was still unknown.

This was a sensible decision because it permitted more scientific and economic research to be conducted and for the community and farmers to express their concerns to government and industry.

GM canola has been grown in the United States and Canada since 1995. To date, there has been no evidence to suggest that there is a risk to the health of humans nor wildlife from growing such crops. In fact Bennett et al. (2004) found that growing a GM herbicide-tolerant crop would be less harmful to the environment and human health than growing the conventional crop, owing to the reduction of herbicide use. Indeed, there are many benefits that can come to Australia from the cultivation of GM crops.

Australia already cultivates GM cotton and carnations. The incorporation of genes for “drought resistance” in wheat and rice for instance could have dramatic environmental benefits, not least allowing us to grow more food with less water. The savings could be returned to our parched rivers and waterways.

Despite the potential benefits, there is a general paranoia amongst extremist environmental groups (such as Greenpeace) that GM-crops are somehow “unnatural” and “dangerous”. Such claims show a complete lack of scientific literacy. The labelling of GM crops as “Frankenfood” is a favourite scare-tactic amongst the environmental extremists.

A good example of the potential of GM was the FlavrSavr tomato, developed by Calgene. When tomatoes ripen, they become soft and are easily spoilt and so are picked green. The softening is caused by a protein called polygalacturonase, which is present in all tomatoes. Calgene scientists simply cloned the gene, flipped it backwards and re-inserted it back into the tomato. This antisense gene then blocked the function of polygalacturonase and the tomatoes stayed firm after ripening. No “foreign” genes were used, yet green groups went berserk and even suggested the tomatoes contained fish genes! (This claim was false).

Golden Rice provides another example of the positive potential of genetic modification. According to the World Health Organisation, dietary vitamin A deficiency (VAD) causes some 250,000 to 500,000 children to go blind each year. As a remedy to this problem, scientists Ingo Potrykus and Peter Beyer developed Golden Rice which contains elevated levels of β-carotene (provitamin A). Rice plants produce β-carotene in green tissues but not in the endosperm (the edible part of the seed). By addition of only two genes, phytoene synthase (psy) and phytoene desaturase (crt I), the pathway was reconstituted and β-carotene is consequently accumulated in the endosperm. The humanitarian benefit of cultivating this rice would be enormous, but for environmentalists objecting to the use of a “bacterial gene” in its development.

The notion that a “foreign” gene poses some risk to health or is unnatural is a myth. Aside from the lack of evidence of this process being dangerous in itself, gene transfer between bacteria and plants happens in nature, such as in the case of Agrobacterium tumefaciens. Sure, if a scientist were to transfer a gene encoding a toxin into an edible plant, that would be dangerous, but only because of the presence of toxin and not because the gene was “foreign”. Given that the DNA code is universal across all organisms and no genes have species-specific identifiers marking them as “plant”, “animal”, “bacterial” et cetera, this fear of the technology is misplaced.

One concern with growing GM canola is that herbicide-resistance genes will ‘contaminate’ non-GM canola crops via cross-pollination, since canola is an out-crossing species. In an Australian study, Rieger et al. (2002) found that canola pollen could be spread up to 3 kilometres away from source plants, but herbicide-resistance genes were present in an average of 0.03% of plants tested at those distances, suggesting that buffer zones could be successfully used where farmers want to grow non-GM canola without fear of contamination. This is especially applicable in the case of Tasmania. Under European standards for instance, “GM free” canola is permitted to contain up to 0.9% genetically modified material.

It is true that the organic sector could be affected by the commercial planting of GM canola, however ABARE currently estimates that organic canola accounts for less than 1% of the Australian canola crop. In any case, the economic debate is one which farmers will need to have and decide upon. This is not an environmental risk, but an economic one.

I believe that the adoption or otherwise of GM crops should be conducted where it is economically and environmentally prudent to do so. If a particular agricultural industry doesn’t want to grow GM crops because they feel their industry can gain higher prices with non-GM, then I support them wholehartedly. But if the environmental return (eg less use of herbicides, less water use etc) and the economic return is greater with GM crops, then as a society we should embrace the technology.

Of course there are risks. One risk is of GM crops hybridising with wild relatives in species where this is possible and wild relatives are present, causing a transfer of new traits (such as herbicide resistance) to these plants. However it is the job of the OGTR to evaluate and regulate new releases and to date, they’ve done an excellent job in risk assessment. Anyone who works in a PC2 laboratory would know how stringent the Gene Technology Act 2000 is.

It is up to affected farming groups, the OGTR, the Food Standards Authority and state governments to decide for each agricultural sector what is best for consumers, industry and the country. Consumers are entitled to stringent labelling regulations on all food, and the choice whether to purchase GM food products.

Genetic modification of crops offers Australia many opportunities and it would be foolish in the extreme to ignore the potential of this tried-and-tested technology and miss out on what it can offer the people of Australia and the world.

Scientific references:

Bennett et al. (2004) Environmental and human health impacts of growing genetically modified herbicide-tolerant sugar beet: a life-cycle assessment. Plant Biotechnology Journal 2: 273–278

DallaPenna et al. (1986) Molecular cloning of tomato fruit polygalacturonase: Analysis of polygalacturonase mRNA levels during ripening. Proceedings of the National Academy of Science USA 83 (17): 6420-6424

Rieger et al. (2002) Pollen-Mediated movement of herbicide resistance between commercial canola fields. Science 296 (5577): 2386-2388

Image credits:

1. Canola field by Neal Sanche, used under a Creative Commons licence.

2. Canola plant by Richard Rosalion, used under a Creative Commons licence.