Scientists from the University of Exeter and Shimane University in Japan have proved for the first time that vitamin C is essential for plant growth. This discovery could have implications for agriculture and for the production of vitamin C dietary supplements.The study, which is now published online in The Plant Journal, describes the newly-identified enzyme, GDP-L-galactose phosphorylase, which produces vitamin C, or ascorbate, in plants. Vitamin C is already known to be an antioxidant, which helps plants deal with stresses from drought to ozone and UV radiation, but until now it was not known that plants could not grow without it. [ read more. . . Study shows vitamin C is essential for plant growth ]
The vitamin C was increased in plants by manipulating genes. I have no idea if giving your plant some vitamin C in plant food will make any difference. The difference in plants exposed to stresses like smog is very impressive. The ones able to produce more vitamin C thrive while the others shrivel.