how do herbicides that only kill a certain plant work.

Question

I’ve been using a weed spray at work that only kills gorse and tobacco trees. How does this work and why don’t other plants die?

In:

Answer 1

Because it targets molecular mechanisms that only exists in some plants. It is unlikely to attack only one single plant species but rather a group of plants, e.g. all grasses. There are however herbicides targeting basic plant mechanisms like glyphosate, which kills all plants, but not animals, since the targeted enzyme does not exist in animals.