When you buy a birthday cake, the goods and services tax (GST) makes the cost of the cake bigger.  If only Mr Hewson could have explained it so succinctly he may have been Prime Minister! There’s another type of GST in plants that do the same thing to herbicide molecules. It makes them bigger and then the whole thing gets smashed to pieces. The GST in plants are enzymes called glutathione-S-transferase.  In other words, they join or transfer the big molecule glutathione onto other molecules. Click through to learn more!