Science Homework Help

You buy a new house and the front yard has some really nice rose bushes, but they are surrounded by lots of weeds! You don’t really want to try and dig them out by hand and your nice new neighbor comes over with a bottle of weed killer.  He says it shouldn’t kill your roses, but you, knowing that weeds and rose are pretty similar physiologically decide to do some research.  You find out the active ingredient in the weed killer causes the stomata close when in contact with the chemical.    What would be the results?  Explain which parts of photosynthesis would be effected and what those effects would be, how would the plant be effected?  Would it be likely to hurt your roses?