The present invention provides a method of producing a plant which exhibits improved growth and/or yield under reduced nitrogen conditions, that is, under cultivation conditions where nitrogen is limited as compared to ordinary cultivation conditions, by increasing 2-OG content in plants. Particularly, the present invention provides a method of producing a plant which exhibits improved growth and/or yield under conditions where nitrogen is reduced, that is, under cultivation conditions where nitrogen is limited as compared to ordinary cultivation conditions, by introducing a GDH gene or ECASPC gene into plants and expressing the transgene GDH or ECAPS in the plants, which results in increased 2-OG, or by spraying proline on the leaves of plants to increase the 2-OG content, thereby enhancing the incorporation of nitrogen or metabolic activity of plants. Also provided is a method of cultivating such plants under nitrogen-limited conditions.