The composition, in accordance with the present invention, for producing a plant body having an improved sugar content includes glutathione, a polynucleotide encoding a y-glutamylcysteine synthetase, or a polynucleotide encoding a glutathione-binding plastid-type fructose-1,6-bisphosphate aldolase. The composition preferably includes oxidized glutathione. This allows the provision of a composition for easily producing a plant body having an improved sugar content.
