Salt is applied to tennis lawns to kill weeds. How does salting tennis lawns help in killing of weeds without affecting the grass?

Salt solution being hypertonic, causes exo-osmosisin plants. 1 cup salt in 2 cup of water, fairly well dissolved when sprayed on weed plants, start killing them. This salt concentration is then increased in subsequent sprays, if the weedsarestill thriving in the field.