Smith's research is directed towards understanding plant growth and development at the molecular level, and seeking ways to improve plant productivity and value. During his PhD studies Smith collaborated with John Bedbrook at the Plant Breeding Institute to clone the first
cDNA encoding a plant enzyme. This enzyme is ribulose-1,5-
bisphosphate carboxylase/oxygenase, abbreviated to
RuBisCO, which is responsible for carbon dioxide fixation by plants. In Edinburgh in the pre-genomics era, he collaborated with
Chris Leaver and cloned several key enzymes of plant metabolism, including malate synthase, isocitrate lyase and PEP carboxykinase. He conceived an idea with
Anthony Trewavas of creating transgenic plants expressing the calcium-sensitive luminous jellyfish protein,
aequorin, to report calcium signalling in plants. Together they obtained funding, created the plants and showed that they could report rapid calcium signalling in response to cold, fungi, touch and wind. This work predated similar research using
green fluorescent protein from the same jellyfish. In 1996 Smith and his PhD student Takeshi Takaha reported the discovery of cyclic glucans containing up to 200 glucose residues, which they named
cycloamylose. Cycloamylose and related cycloglucans are now used extensively in food and biotechnology industries. Further research on starch metabolism with Alison Smith and Sam Zeeman at the John Innes Centre led to the discovery of a novel pathway of starch breakdown in leaves. Smith was also instrumental in defining pathways of energy metabolism involving peroxisomes, particularly fatty acid
beta-oxidation and the
glyoxylate cycle. == Karrikins: a new family of plant growth regulators ==