PLANT LIFE
Given an opportunity, a depleted cultivar will happily take back its genes, and the last thing a farmer wants to watch over is a carefully cultivated crop reverting to nature. Another reason why farmers become protective of their crops is that while the flowers attract pollinators, the roots act like a magnet for the carrot fly, Psila rosae. Anyone who has tried to grow carrots in suburbia, is likely to be familiar with this pest, the grubs of which burrow into the roots, which being tossed aside in disgust, simply let loose the larvae to pupate into the next generation. In one season, the crops can be attacked twice, and as if this were not bad enough, the grubs can hide out in the wild relations while awaiting a return to the more succulent cultivars. The purple colouring of the eastern carrots comes from water soluble pigments known as anthocyanins, but in the western orange varieties, these are replaced by carotenoids. Those bright colours are important to us. The parental command to, “eat your carrots” is usually followed by the homely advice that “they are good for your sight.” True, for the carotene that gives carrots their bright orange colour, helps to make the visual pigment, rhodopsin, and without rhodopsin we would not be able to see. The millions of rods and cones that line the back of our eye depend completely on rhodopsin’s reversible reaction to light. Oddly enough, for something so essential for sight, we have a blind spot when it comes to synthesising this essential chemical. We have a missing link in the chain of reactions, so without a top up of the A vitamins with their carotene precursors, we can actually go blind. Normally, this is not a problem in this part of the world, but in many countries where a diet, lacking vitamin rich greens, is poor, loss of sight is all too common. According to the World Health Organisation, a third of the world’s children under the age of five are deficient in vitamin A, and up to half a million a year go blind because they do not have the essential precursor of rhodopsin. wild Daucus carota from the cultivated plant.” A variety of cures are attributed to the wild carrot, but as is usually the case, distinguishing between the real and the imagined is next to impossible. The scientific literature presents a bewildering array of biochemicals, many of which could have an influence on our health, and an aromatic oil is produced for commercial sale by steam distillation of the seeds. One of the widespread traditions, going back to Hippocrates is that carrot seeds act as a contraceptive, and some researchers, basing their claim on tests with mice, think that some of the constituents may act by disrupting the implantation of the fertilized ovum. Another widespread belief is that wild carrots make good companions for tomato plants making them grow better. At a Young Scientist exhibition, about 25 years ago, two students, Anne Phelan and Cathriona Delaney from Tipperary presented an all too rare glimpse of how plants, such as the wild carrot, were looked upon in the not too distant past. One of Anne’s relations, John Walsh, had kept a scrap book of herbal cures. In neat copperplate writing, John had noted that wild carrot with equal parts of Yarrow, Blood Wort, otherwise known as Herb Robert, and another plant, whose name I could not make out, could be boiled up and strained to give a drinking cure for back-pain. Apart from the difficulty in defining what exactly constitutes a back-pain, this, like so many other claims and beliefs, this would be hard to verify without undertaking a battery of scientific tests, but that’s exactly how some of the world’s most potent drugs were ‘discovered’. With tradition, old is usually best. While we can ignore the silly modern fads, long established folklore is often a good indicator that there is something worth investigating.
The spreading umbrella of Daucus carota, and below the same plant in County Mayo beginning to close up into a cage. Carrots, like other foods, are not just eaten to fill the stomach, and while sharing the role of providing us with enough carotene is important, they are also among the many plants that were valued as herbs. In their book, Medicinal Plants in Folk Tradition, the authors, Allen and Hatfield, having gone through the records of England, Scotland, Ireland and Wales, noted that “folk tradition on the whole carefully distinguishes
SCIENCE SPIN Issue 48 Page xx