Pilchuck Chapter ARS

My Christmas letter to Santa begged for a can of the perfect herbicide – one that would kill plants but be perfectly harmless to animals; that would not persist in the environment but decompose rapidly to harmless residues; something that I could chug-a-lug with impunity.

So what happened?  Well, Santa did leave a 10 liter container of concentrate under the tree (we have nearly 11 acres) and a note that read:  “Dear Little Joe, I get this request all the time and the herbicide you want is readily available, so I did not have to bother the elves to invent anything new.  Happy gardening,  Santa:   Needless to say, I was delighted.

Looking into the history of what I received I found that in the 1960’s or earlier a group of scientists did a survey of all the reactions that plants have to carry out (and this is a huge list since plants have to synthesize everything from carbon dioxide, water and a few elements), but which animals did not.  The logic behind this search was that if a reaction going on in plants could be stopped, this might be fatal to the plant.  But if animals did not carry out this reaction then there would be no effect on them.  Ergo – the perfect herbicide.

What they found was the Shikimic Acid Pathway (SAP).   To give an explanation, the SAP is long chain of reactions leading to the production of the three essential amino acids that possess an aromatic (benzene) ring.  Block a single enzyme in this long chain and none of these three amino acids are produced, with fatal results to the plant.

So why is this particularly obscure bit of knowledge useful?  Well, plants use SAP but animals don’t.  Why don’t animals possess SAP?  They get their essential amino acids by eating either plants or other animals.  So, the scientists speculated, if we can block SAP in plants they will develop deficiencies of these amino acids, but animals will not be affected.

The search was on for an enzyme blocker, one that would stop a single reaction in the SAP.  The reason for targeting an enzyme is because enzymes exist in extremely minute amounts in cells so the quantity of specific enzyme blocker required will be correspondingly minute.  This could lead to an effective herbicide if such a substance could be produced economically.

So, the race was on.  There were potential profits to a company whose scientists could come up with a SAP-enzyme blocker.  Who won?  Monsanto, with the patenting of a chemical they named glyphosate—more commonly known as Roundup.