Plants infected with genetically-modified (GM) viruses could become industrious factories for medicines and vaccines. The viruses would be engineered to produce useful proteins and the key, said Professor Michael Wilson of Horticulture Research International in Warwick, England, is the prodigious rate at which viruses can replicate themselves. Plant virus can make a million copies of itself in a single cell and each can have 2,000 coat proteins. This huge rate of reproduction means that 50% of the total mass of the plant could be the desired protein. Using plants in this way as sunlight-driven factories could produce cheap, edible medicines and vaccines for livestock or people. It is also possible to alter biological pathways in the plants so that the virus-manufactured proteins are used to create secondary products. Melanin, which could be used in sunscreen products has already been produced in this way.
I think this is better to have a plant factories, than humans going around to collect herbs to make into medicines. As factories could produce cheap, edible medicines and vaccines for livestock or people. To my opinion, having a plant factories is better and can produce own medicines.