If all plants on earth went extinct except for grasses would the human race die out?

Eventually we would most likely die out. Other plants are very important to the food chain. If the producers of the food chain (plants) were to become extinct, those organisms higher on the food chain that rely on plants other than grass would become extinct. Eventually, humans, being the top of the food chain, would not have any organisms to consume for energy (other than grass). Therefore, we would die out. One might argue that humans could simply only consume grass; however, grass doesn't not provide enough nutrients for the human body.