Sunday, May 10, 2009

Fasciating dandelions


I wasn't planning on making the first blog item about dandelions, but there they were, the only green thing in my plot when I turned up at the garden today. The grading was finally done and I was fired up to get the plot planted before I leave on May 12 for a month in New Zealand with 25 Augsburg students, who'll be studying Biodiversity and Environmental Politics. However, before I could plant, something had to be done about the dandelions. I briefly considered collecting leaves and making myself a dandelion salad, but opted out when I recalled the bitter taste from when I had them a long time ago, as an impoverished student. I started to dig and pull, grateful for the excellent loamy soil which made the task easy, and for the income that enabled me to eat weeds by choice, not necessity. Then I saw something interesting: one of the dandelion flowers looked different from the rest. As a geneticist, I am attuned to variation, and this specimen (see first photo below) looked strikingly different from the very uniform flowers one normally associates with dandelions (above). This one had clumps of florets that appeared to be erupting from the center of the flower head. And even more strikingly, the stem was much thicker and broader than typical dandelion flower stems. To determine whether this was an isolated occurrence, I abandoned all thought of weeding and instead spent the next few minutes poring over hundreds of dandelion flowers growing in and around the garden. Most were indeed normal, but I found two other examples of deformed dandelion flowers, with one (in plot 27?) being particularly striking in that another flower head appeared to be emerging from the interior of the first flower head (see second photo below). The other, still growing on the edge of the compost heap for anyone who wants to take a peek over the next day or so, resembled the first one I spotted, implying this was not an uncommon phenomenon in our community garden. When I dissected the fattened stem of the deformed flower growing in my plot, I observed an internal stem growing entirely encased by the outer stem. So what was going on? Aliens? Toxic waste? No one really seems to know, although the phenomenon has been given a name (fasciation), and is not uncommon, having been observed in over a hundred plant species, including the striking crested saguaro cacti. Fasciation can be significant horticulturally: a mutation in a fasciation gene underlies the five-hundred-fold increase in size of beefsteak tomatoes over their wild predecessors.
Fasciation has been attributed to wounding, insect or bacterial attack as well as to genetic mutation, and results in disruptive changes to the apical meristem, the growing tip of the plant that normally grows in an orderly point. Without further study, we cannot be sure why fasciation is occurring in the dandelions of the Augsburg Community Garden and elsewhere, although if anyone is going to be around over the next month and can collect some seed for me, I'd be interested in testing the genetic mutation hypothesis by deliberately planting dandelions in my plot next season!

1 comment:

  1. That's one strange looking dandelion!

    For more tasty dandelion greens, look in shady areas for leaves with out shark "teeth."

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