In their study published online in The Plant Journal, the researchers have described 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.
"Vitamin C is the most abundant antioxidant in plants and yet its functions are poorly understood. By discovering that the new enzyme is encoded by two genes, we were able to engineer vitamin C-free plants and found that they were unable to grow," said lead author, Prof. Nicholas Smirnoff of the University of Exeter.
He said the discovery could have implications for agriculture and for the production of vitamin C dietary supplements.
Prof. Smirnoff said the discovery has also identified the new enzyme as a key player in controlling vitamin C accumulation in response to light.
Vitamin C provides protection against the harmful side-effects of light during photosynthesis, the process by which light energy is used to convert carbon dioxide into plant matter.
"The discovery is exciting for me because it is the culmination of a long-term research programme on vitamin C in plants at the University of Exeter. It opens new opportunities to understand fundamental growth processes in plants and to improve plant resistance to stresses in a changing climate.
In the longer term I hope that it will contribute to the efforts of plant scientists to improve crop yield in a sustainable manner," Prof. Smirnoff added.