Abstract: The present invention relates generally to the use of plants as bioreactors for the production of molecules having useful properties such as inter alia polymers, metabolites, proteins, pharmaceuticals and nutraceuticals. More particularly, the present invention contemplates the use of grasses, and even more particularly C4 grasses, such as sugar-cane, for the production of a range of compounds such as, for example, polyhydroxyalkanoates, pHBA, vanillin, indigo, adipic acid, 2-phenylethanol, 1,3-propane-diol, sorbitol, fructan polymers and lactic acid as well as other products including, inter alia, other plastics, silks, carbohydrates, therapeutic and nutraceutic proteins and antibodies. The present invention further extends to transgenic plants and, in particular, transgenic C4 grass plants, capable of producing the compounds noted above and other products, and to methods for generating such plants.