Glyphosate is a chemical that we hear a lot about these days, but what does it actually do to plants?
The bramble leaf below has been treated with glyphosate and shows the usual pattern of loss of chlorophyll from the leaf, with only the leaf veins retaining the chlorophyll.
For comparison, the leaf below was left untreated and the chlorophyll levels are uniform across the whole leaf.
Why does glyphosate produce this pattern of pigment loss?
According to the Wikipedia, "Glyphosate's mode of action is to inhibit an enzyme involved in the synthesis of the aromatic amino acids tyrosine, tryptophan and phenylalanine.".
I've been trying to figure out why the loss of these amino acids specifically leads to the loss of chlorophyll but the information is not leaping out at me. Possibly it just stops the plant from being able to make most compounds. As chlorophyll needs frequent repair and replacement, and because it's absence is very obvious, the loss of chlorophyll may just be the thing that we see first. I haven't been able to find confirmation of this online. Mysterious! I will keep looking.