Abstract: The invention relates to a process for developing plants of novel type being capable of nitrogen-fixation also in their leaves. The process of the invention comprises inoculating plant protoplasts, cells, tissues, embryos or organs grown and/or treated under in vitro conditions with bacteria belonging to the family of Azotobacteraceae, then cocultivating the thus-obtained culture at a temperature of 15.degree. to 35.degree. C. and, if desired, propagating and/or regenerating the whole plant under in vitro conditions on or in a culture medium containing nitrogen and main carbon source(s) utilizable only by the plant cells as well as optionally other additives. The process of the invention ensures a well-balanced growth of the plant together with the bacteria.