February 18, 2015

Plants vs. the World

Alexis St-Gelais, M. Sc., chimiste - Discoveries

Climate can be rough around here, in Saguenay. With temperatures regularly dropping under -25ºC, February is way colder than the average, this year. Fingers get nimble very quickly, and the tip of your nose can freeze within minutes. Although this might not be comfortable every day for us, Humans, other living beings have it a lot harder than us these days: plants! Many die out every year, but dozens of species survive years and years of biting cold, only to bloom again next spring.

This is only one aspect of the perillous life of a plant. Indeed, when you think about it, being a plant is simply a pain. Of course, you can feed autonomously, but on the downside, you usually have no way to move from where you stand. This implies that you will be heavily challenged. Not only can you be preyed upon by any herbivory passing by without being able to anything: there is also no way to escape extreme temperatures, intense sunlight and its deleterious UV rays, or unusual variations in what you'd expect from your soil, like pollution. Throngs of fungi, bacteria and viruses want to rip you apart. You can be trampled by anytime by even the most pacific moving being coming around. And except in the most extreme environments, you are likely surrounded by a very diverse neighbourhood, among which you will find many other plants that would rather see you dead as to gain some space for their own growth or their seedlings'.

Plants can not move, and as such, they had to develop at times impressive adaptations to cope with their situation. Some are physical, such as a thick bark against fire or spikes to discourage herbivories. But chemistry is a wonderful tool to defend yourself, in such a situation. Plants thus produce a tremendous diversity of chemical compounds, far beyond what can usually be found among animals.

Photo of plant diversity  - Photo credit : Wikimedia.org


Animals and Plants share some building blocks: proteins, lipids, sugars and aminoacids (constitutive of DNA) are as such considered to be primary metabolites, which contribute to the very structure of life in general. But plants may also count on what has come to be known as secondary metabolites, which in fact encompass almost everything else that we encounter in vegetals: phenolic compounds, terpenoids, saponins, alkaloids, complex polymers... And although if science does not understand much of their functions in plants, it is thought that they serve as defense against herbivories, bacteria and fungi, contribute to wound healing, play a role in interactions with insects, and may even be implied in plant-to-plant communications. I will present some specific cases in upcoming posts.

These are the "useful" molecules that we are often referring to when we think of natural products. Many of them have some interaction with our biological functions, which can be detrimental or beneficial. Thus, next time you sip a good coffee and feel the energizing effect of caffeine, enjoy the soothing scent of eucalyptus oil in case of cough or buy ginseng extracts to boost you up, have a thought for the harsh life of plants!

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