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wicked_plantsToxic? Yes!….. But wicked?

Wicked (wik’id) adj. [Middle English wikke, evil, akin to Old English wicce, witch] “1. morally bad or wrong; acting or done with evil intent; depraved; iniquitous.” – Webster’s New World Dictionary

A wonderful new book Wicked Plants: The Weed That Killed Lincoln’s Mother and Other Botanical Atrocities by Amy Stewart, which I just finished reading, describes the myriad of chemical compounds found in some plant species that are toxic to animals – especially humans. Of course, such toxic plants aren’t evil or “wicked”. They’re just passively defending themselves against herbivores.

But calling them “wicked” certainly attracts more attention and sells more books, no? And isn’t it a good thing that more people would then learn about plants? So, fair enough.

Perhaps an interesting question to consider is why these plants have come to produce such toxic chemicals.

belladonnaThese “Wicked” Toxic Chemicals are Plant Secondary Compounds

It may come as a surprise to you that most of the basic metabolic pathways found in your cells – glycolysis, respiration, protein synthesis, etc. – are also found in most plant cells. Plant and animal cells likely share a common ancestor – a primitive eukaryotic cell. Thus, both plants and animals have many of the same so-called primary (a.k.a., “housekeeping”) metabolic pathways.

But, since plants don’t eat stuff, they have to make all the specialty organic compounds, such as amino acids, vitamins, pigments, etc., that they need to function well.

Therefore, plants not only have the “primary” metabolic pathways, but also so-called “secondary” metabolic pathways. That is, plants have special (secondary) metabolic pathways to achieve special functions, such as protecting themselves from UV light, chemically attracting pollinators, surviving periods of drought, etc.

Plants Can’t Pee, So They Have to Recycle or Store Their Secondary Metabolic Byproducts

If you ever took an organic chemistry class, you make recall that in chemically synthesizing an organic compound, you would sometimes generate chemical byproducts. Plants do this, too. But how do they get rid of them?

smokerOften, they store these byproducts of secondary metabolism or “secondary compounds” in the vacuole of plant cells. The vacuole sometimes functions as the plant cell’s “garage”.

If one such secondary compound turns out to be nicotine, for example, which just so happens to be toxic to some insect herbivores, then it’s a lucky break for the plant. By chance, an evolutionary selective advantage for the plant has occurred.

And if this compound also turns out to affect humans, then this also may be a lucky break for the plant. (Nice to be cultivated.)

So most, if not all, of the toxic compounds mentioned in “Wicked Plants” are secondary plant metabolties stored in the vacuoles of plant cells. When the plant is eaten, or if trichomes on the plant surface are crushed by contact, the toxic compounds are released, which deter (or, in some cases, inter) potential herbivores.

All just by chance.

No evil or “wicked” intent involved.

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