Pinball wizard longing for mellow yellow (aka more than you wanted to know about Brassicaceae)
Is this scenery I can love, given these farmed plants displace the native orchids I was out here seeking? Perhaps I can focus on the river red gums, set off beautifully in this buttery sea. But then those gums are sentinels, says Lynda who is with me, with no offspring. That can’t be a good thing.
So back to the canola. Are they genetically modified? Of course, in a technical sense, given nearly all crops are selected and bred from wild ancestors of a number of Brassica species (e.g. napus, rapa and juncea). With molecular manipulation we can do that faster, and more precisely, and there are consequences. Yet I found Mark Lynas’s arguments in Seeds of Science convincing: GMOs are not intrinsically a bad thing.
Then in flew images of canola flowers, with those distinctive four petals you find in the cress family. Followed by fruits, of all shapes and sizes, among its relatives. Then the shiny brown and black seeds, were padded away.
A few years back (turns out it was 17 years ago, but who’s counting?) I wrote something for the then Friends of Royal Botanic Gardens Sydney magazine, The Gardens, in praise of the canola plant family, Brassicaceae.
I reminisced (even then) that the Brassicaceae was the last taxonomic account I had prepared for the Flora of Victoria series before I left Melbourne, four years earlier, and that it was once known as Cruciferae due to the cross-like arrangement of the four petals. The family is not a favourite among botanists, I said, and there wasn’t a queue of authors waiting for the privilege to tackle this group.
The rest of the article (lightly edited) seems worth repeating here, despite covering bits of it in a previous post, Called for calling a cabbage a cabbage). This exposition may be a nice foreground, I think to myself, to a selection of pictures I took on that September trip, along with two at the end from the banks of the Yangtze River in China, back in March 2004.
The Brassicaceae includes a lot of weed species, most of them unremarkable with small pale flowers, and with the reputation for being difficult to distinguish from one another. The family’s profile among naturalists and specialists alike is not improved by nearly every identification key starting with ‘Fruit a siliqua or silicula?’ followed closely by ‘Cotyledons conduplicate or not?’.
However, the family does appeal to some scientists. Arabadopsis thaliana, the Thale Cress, has been a favourite with plant geneticists; it could be described as the ‘fruit fly’ of botany. Arabadopsis hit the cover of the prestigious scientific journal Nature when it became the first plant to have its genetic code fully mapped.
It's a relatively tiny genome, one-twenty-fifth the size of the human genetic blueprint (although note that the genome of some plants, like maize, is similar in size to our own). Which is why, along with its short life cycle and prolific seed production, Thale Cress was selected for this honour.
Prolific seed production is also a key to Brassicaceae appearing in the top 10 of the most economically important plant families. Mustard and Canola Oil production chew up the product of over a million hectares of yellow-flowering Brassica in southern Australia.
In fact, it’s hard to go through a day without either eating or stepping on a ‘crucifer’. Even so, you may not have noticed what all the crucifers have in common that makes them one of our most easily recognisable families. The symmetrical four petals (only rarely missing) are followed by an equally characteristic fruit, a two-lobed capsule that usually splits from below.
The capsules fall into two main types, the elongate ones (technically more than three times as long as wide) called silquas, and the squat ones called siliculas. There are almost always fruits present in the weedy crucifers and taxonomists make good use of fine details of the embryo within the seed.
The conduplicate business is all about how the seed leaves, the cotyledons, are arranged within the seed. If they are lying flat together, they are conduplicate. If they are otherwise folded or arranged, they are not. You are now on your way to identifying the world’s 350 or so genera of Brassicaceae.
You could start with your vegetable garden or crisper. One species alone, Brassica oleracea, has been responsible for staples such as Brussels Sprouts, Cabbage, Cauliflower, Broccoli and Kohlrabi. The fruits are all long and narrow, and the cotyledons…conduplicate.
Then step outside. In the lawn or at the edge of garden beds or paths you are sure to find Bittercresses (Cardamine species) or Shepherd’s Purse (Capsela bursa-pastoris; look at the silicula to understand the name!), particularly in winter. Out of town you might notice road-side verges glowing with the bright yellow flowers of runaway yellow-cress, mustards, turnips and rapes and canola. In the paddocks too of course.
In the garden proper you may have Honesty, Wallflower, Candytuft, Alyssum or Stock, all Brassicaceae of overseas origin. Native to Australia we have a few small genera, and 35 species of native peppercresses in the genus Lepidium. Then there is the rare Ballantinia antipoda from Mount Alexander, in central Victoria – you can read about that one in a earlier post, Rare shepherd's purse coming to a hilltop near you.
You can categorize their fruits yourself, but for really weird siliculas, try the Donald Duck head of Ward’s Weed (Carrichtera annua) in semi-arid areas, and the Conquistador helmets of Sea Rocket (Cakile species) on our sandy coastlines.
It’s a big family, with over 3500 species around the world. There is a strong motif of practicality and dependence running through our relationship with the Brassicaceae. We eat them, we study them and we weed them from the garden. They are often not pretty—although their fruits have a certain elegance and symmetry of design—but they are always with us.
That’s how I finished my piece for the Friends. On the highway, in western Victoria, my mind eventually gave way to the sheer beauty of these fields of yellow punctuated by one of the most beautifully ugly trees on Earth. Serenity now.
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