27 November 2011

Welwitschia: curious cone-bearer of the Namib

This is no ordinary tree trunk.

It was a hot afternoon during my freshman year and I was trying to find my botany professor's office. Sweat running down my spine, already late for organic chemistry, lost in the basement of the Botany building. I turned a corner and came face-to-face with the giant, scalloped remains of a welwitschia, mounted on a pedestal. Clutching the ethnobotany paper I was meant to submit that day, I just stood there, enraptured, mesmerized. It resembled something creepily organic, like Martian fungus, or at least something indecent that had sprouted from the sea floor. Certainly not a tree trunk. I never made it to organic chemistry that day.

Welwitschia mirabilis makes the scorching Namib desert its home.

Not only is Welwitschia mirabilis the solitary member of its genus, but it is also the only member of its family, the Welwitschiaceae. In fact, it is taxonomically so bizarre and so unique that it has been given its own order. The only other species that appear to be (quite distant) kin are the joint-pines of genus Ephedra. Wait, did I say joint-pine?! Yes, I did. For the welwitschia is a short, stunted gymnosperm and bears its seeds in cones, just like pines, firs and spruces. Think about that for a while. This weird tree is found only in the Namib desert of Namibia and Angola, a habitat as different from a dark northern forest as any, the oldest desert on the planet. It is estimated that welwitschias have been growing here for nearly 100 million years, and that they haven't changed much during that time. The welwitschia has many fascinating adaptations that allow it to thrive in this harsh climate. It survives in places where it sometimes doesn't rain for years, subsisting solely on the fog that rolls in from the Atlantic at dawn.

Alien vegetable forms dot the landscape inside Messum Crater, Namibia.

Its short woody stem is unbranched, but grows wider with age to form a crenulated woody bowl that can be a meter in diameter. Like most moisture-dependent desert plants, welwitschias are pretty slow-growing: it is estimated that large specimens with leaves in excess of 6 m long may be more than 1,500 years old. From the margins of the crested stem sprout what appear to be a myriad of strappy leaves. 

A large specimen in the Namib-Naukluft National Park.

Their appearance is deceptive. In fact, the welwitschia only produces two opposing leaves that continue to grow throughout the life of the plant, becoming split and shredded through the action of sand and wind and centuries. The shredded leaves become a trap for wind-blown debris, enriching the sandy soil around the plant and providing shelter for insects, spiders and lizards. Welwitschias have a large taproot to pull moisture from deep underground, and also a network of short fibrous roots near the surface to help them absorb water from ocean fog that condenses on the leaves and rolls to the ground. In a way, these plants engineer their own microclimate to ensure their survival in extremely arid surroundings.

Welwitschia bugs on the cones of a female plant.

As I mentioned, the reproductive structures of Welwitschias are cones, like those of cypresses and cycads. Male and female plants exist separately, bearing different types of cones. Male cones produce pollen, but not in copious amounts like those of wind-pollinated pine trees do. Instead, they rely on insect pollinators to carry their precious cargo to a receptive female plant. The plants are often found crawling with yellow or vermilion coloured welwitschia bugs, Probergrothius sexpunctatis, attracted by the sweet nectar secreted by the immature cones. However, these bugs don't seem to be the pollinators, and other insects have been suggested as the culprits, including flies and wasps. In the unforgiving desert, welwitschias have maximized their chances of survival, especially at the vulnerable seedling stage. When released from mature cones, welwitschia seeds may remain dormant in the sandy soil for several years until heavy rains come to the Namib. Only then does a new generation of Welwitschia mirabilis germinate. All in unison.  

Picture credits:
Welwitschia trunk by Routard05
Welwitschia in habitat by Derek Keats
Messum Crater by intelligentinfo
Naukluft specimen by Joachim Huber
Bugs on cones by Jerry Oldenettel

7 November 2011

Tasting fractals: true confessions of a synesthete

Matcha green tea caramels: a volcano of taste.

We were at a bar, discussing the latest lab gossip over flutes of winter ale, when Lyndsay suddenly dug through her bag and presented me with a small, square piece of green candy, wrapped in clear cellophane.
'Our postdoc brought me some of these caramels from Japan,' she said. 'This one's green tea. You should try it.' So I did. An interesting and delicious combination of buttery caramel and invigorating matcha green tea flooded my palate.
'It tastes sort of this shape,' I said, miming a mountain with my hands. 'Sort of...volcano-like. It's rounded, but there's a pronounced indentation at the top where the green tea and the butter caramel intersect.' Both Eric and Lyndsay stared at me as if I'd just confessed to setting a toddler on fire.
'So tastes have shapes to you?' Eric asked.
'Well, kind of,' I said. 'They're more like landscapes than free shapes.' I hesitated. 'But we all have that, right? It's not like I have synesthesia or anything like that.'
'No, Leon, no one else has that,' Lyndsay affirmed. 'No one else tastes shapes.' Eric just laughed, shaking his head furiously. As the first snow of winter started sifting down from pink clouds hugging the town, I started to reconcile myself with the fact that I may have synesthesia.

People with synesthesia show increased connectivity and communication between parts of the brain normally devoted to the processing of different sensory stimuli.

Synesthesia is commonly defined as a neurological condition where stimulation of one of the senses elicits involuntary triggering of another sense. People with synesthesia are dubbed synesthetes, and synesthesia can take many different forms. Some people experience vivid colours when hearing specific sounds (C sharp on the piano sounds golden yellow). Others associate personalities with numbers (4 is such a guarded, introspective number). Still others might associate textures with specific smells (sandpaper smells like strawberries). Much research has been conducted on the cause of synesthesia, suggesting enhanced cross-talk between brain areas usually devoted to separate sensory pathways (see here for an extensive reference list, both peer-reviewed and otherwise). For example, when people who experience coloured-hearing synesthesia are stimulated with spoken words while inside an fMRI, the areas of the brain devoted to the processing of colour information light up like they were watching the psychedelic Star Gate sequence from 2001: A Space Odyssey. The brains of control subjects who don't have synesthesia do not light up in this way, even when they were extensively trained to associate words with specific colours. Science is also beginning to make some progress on the genetic basis of some of the more common forms of synesthesia, with evidence from large-scale genome-wide association studies implicating specific regions on several different chromosomes.

Hearing colours can be quite the space odyssey.

But what about me? My apparent synesthesia has not been confirmed by a neurobiologist, and I've had none of my genes sequenced. Synesthetes are more likely to be left-handed. I'm left-handed. About 40% of synesthetes have a close-relative who also has synesthesia. I...well, I don't know. I've never asked them, and perhaps they, like me, haven't thought it anything unusual and therefore never mentioned it. Also, my kind of synesthesia, morphogeusia (from Ancient Greek morphe, 'form' and geusis, 'taste'), seems to be one of the weirder ones. In addition to taste, it also involves my sense of smell to some extent. I once started to describe the scent of a colleague's perfume as 'very tall, sort of skyscraper-shaped, but with a top that resembles a bisected sphere with indentations...' before trailing off when I saw her raised eyebrows.

Ceylon black tea.

Let me explain what is happening to me. Basic tastes and flavours have pretty basic shapes, and these shapes are not so much felt as seen; they're topography, not texture. All fats and oils elicit the same perception of rounded mounds. Butter is distinctly dome-shaped. This partially explains why those buttery green tea caramels tasted volcano-shaped: it's that mountain of buttery goodness! The taste of rooibos is also rounded, but concave in contrast to the convex dome of butter. Rooibos is therefore bowl-shaped to me, and able to contain other flavours (like the bullets of vanilla), whereas the domed heavy cream of a crème brûlée would go over the top of vanilla. Incidentally, real vanilla is fat and short, whereas artificial vanilla is taller and thinner, more like a rifle cartridge. I had a fine cup of black tea the other day that tasted much like a flight of stairs. Sharp, pungent ingredients like raw onions or wasabi tend to taste like valleys or canyons, and the sharper they are, the more sheer those cliff faces become.

Eggs over easy.

Initially, I took that fact that not every taste seemed to have a shape as evidence that I didn't actually have synesthesia after all. Surely everything must elicit a well-defined topography! But then I realized that it's merely harder for me to see the shapes of things such as eggs and french fries; it's not that they lack landscape, it's just that the topography of that landscape is really shallow. French fries are just shallow ripples, whereas an egg forms a shallow depression, like a dried lake bed. Perhaps surprisingly, the extent of a synesthetic shape does not correlate with my enjoyment of a particular foodstuff. I like both eggs and french fries and don't find their taste one-dimensional, regardless of how shallow and dull their synesthetic features are.

Tart cherries, with a lingering oak finish.

While still an undergrad, I was recruited to a university tasting panel by a friend majoring in food science. Soon my palate was required to evaluate all manner of things, from frozen vegetables to chocolate milk. The sensory evaluators commended my vivid gustatory descriptions for new flavours of potato chips they were developing (though I was careful not to describe them as 'salt flats with interspersed pyramids' or anything similar). However, I'm not a supertaster by any means. Neither do I possess a particularly sophisticated palate. All wine resembles a generic jungle canopy to me. It's as difficult for me to tell one pinot noir from another as it is difficult for me to discriminate between a rain forest from Bolivia and one from Ecuador. Highly complex flavors elicit landscapes that are not very memorable and exceedingly difficult to describe, like the faces of strangers you meet in a dream. What synesthetic shapes did that chilli verde from the other night conjure up? I don't recall exactly, but there was some granularity, I'm sure...

So that's my little personal subjective anecdote about maybe perhaps having synesthesia.
'I'm so happy for you,' a lady in a tea shop said to me the other day, when she overheard me discussing my synesthesia with Eric. 'What a wonderful talent.'
'I'm not sure I'd consider it a talent, as such,' I responded. 'It's not even particularly useful. I'd read about Daniel Tammet, who has high-functioning Asperger syndrome and uses the vivid synesthetic landscapes generated by numbers to recite pi to tens of thousands of digits. I don't have that at all. I'd rather be good at math.'
I didn't tell her about lemons and how they taste like fractals, though. But they do that for everyone, right?

Picture credits:
Matcha green tea carmels from Fusion Sweets
MRI scans from Rouw & Scholte (2007) Nature Neuroscience 10:792-797
Star Gate sequence from 2001: A Space Odyssey (1968)
Stone steps from Steve McCullough
Dry lake bed from Reno Tahoe
Jungle canopy from thaths