Answered Dec 18, 2017
I am guessing that you mean, “If all the plants disappeared right now”(?)
All humans and other terrestrial animals (e.g. livestock like cattle and chickens) would starve to death. Most people would be dead within a year, from immediate shortages, and competition/conflict over dwindling resources.
Anyone living longer would need to have stockpiles of grains, rice, canned goods, or other long-shelf-life food. They would still die when that ran out.
On a very long-term scale, the atmosphere would change, due to the lack of CO2 uptake, and the lack of O2 being pumped out.
All animals (including carnivores) are directly or indirectly dependent on plants.
On a more positive note, many of the bacteria, archaea, and fungi would still survive, although the balance of particular species would gradually change with the new environmental conditions.