Wednesday, May 2, 2012

There's pansies, that's for thoughts

Species name: Viola tricolor

Common name: Wild pansy, Heartsease, Johnny Jump Up

Location: Nova Scotia

This species of pansy is native to Europe, and is the genetic basis for all commonly planted garden pansies. The wide variation in colour (white, yellow, orange, golden, purple, blue, variegated, etc) in these garden plants is due to selective breeding over hundreds of generations, not due to genetic modification using modern technology. They're a great example of the effort that we as humans have put into moulding plants into our idea of beauty.

Pansies are perennial plants in the right environment (no frost), and annual in others. The wild varieties that haven't been selectively bred are much more cold-tolerant and can survive as perennials in much less hospitable environments. In Ontario, we get wild pansies popping up as forest ground cover near river banks and in forest lowlands despite our (often) very cold winters (except not this year!). Since their introduction to North America as a decorative and medicinal plant, the pansy population has exploded and has become an invasive plant.

Pansies are a great example of coevolution between bees and flowers requiring pollination. Their purple colour attracts bees (who see in the ultraviolet range) like a glowing beacon. The yellow portion in the interior of the plant would be a dark spot against the glowing background, directing the bees to the nectary of the flower. While the bees are feeding on the plant's nectar (which they will later turn into honey), the flower is depositing pollen behind the bee's head. The bee would then travel to another flower, depositing that pollen onto the female parts of the next flower and ensuring cross-pollination. A good rule of thumb to figure out what kinds of flowers are pollinated by what methods is to look at the colour of the flower and pay attention to the smell: bright red tube-like flowers (and some darker pink ones) are almost always pollinated by hummingbirds, butterflies and moths, purple flat flowers are almost always pollinated by bees, purple tube-like flowers are almost always pollinated by butterflies, dark red smelly flowers are almost always pollinated by flies, and white flowers are the "grab bag" of the plant world depending on their smell.

The wild pansy has been used for hundreds of years as a medicinal plant, hence its other common name: heartsease. Historically it has been widely used as a treatment for epilepsy and asthma, and more recently as a herbal treatment of cancer. Pansies contain chemicals called cyclotides in their tissues which have been shown to be cytotoxic (meaning they induce cell death in rapidly-dividing cells). Whether or not the plant contains potent enough cyclotides or whether or not these chemicals are biologically active is still under investigation. I doubt "eat wild pansies" will become a treatment of cancer any time soon. But medicine has to start somewhere! Another great example of why medical researchers need to have a solid understanding of botany in order to come up with new, cheap drugs for various medical conditions. The wild pansy has also been used as a treatment for skin diseases, bronchitis, whooping cough, rheumatism and cystis. Despite the plant's demonstrated anti-inflammatory abilities in rats, it hasn't ever been demonstrated as being effective against any of these health problems. The flowers are actually edible, and are now becoming more and more popular as a garnish on summer salads and as a wedding cake decoration.