Abstract: Plants, particularly cereal plants, which have improved ability to synthesise starch at elevated or lowered temperatures and/or to synthesise starch with an altered fine structure are produced by inserting into the genome of the plant (i) a gene(s) encoding a form of an enzyme of the starch or glycogen biosynthetic pathway, particularly soluble starch synthase and/or branching enzyme and/or glycogen synthase, which display an activity which continues to increase over a temperature range over which the activity would normally be expected to decrease, and/or (ii) a gene(s) encoding sense and anti-sense constructs of enzymes of the starch biosynthetic pathway, particularly soluble starch synthase and/or branching enzyme and/or glycogen synthase, which alters the natural ratios of expression of the said enzymes or inserts enzymes with special structural characteristics which alter the natural branching pattern in starch.

Abstract: A plant which produces polyhydroxyalkanoate polymer has a recombinant genome which contains one or more than one of the genes specifying enzymes critical to the polyhydroxyalkanoate biosynthetic pathway which occurs in certain micro-organisms such as Alcaligenes eutrophus which naturally produce same. The plant species is preferably an oil-producing plant.