Abstract: A comparison experiment with one non aromatic and three aromatic varieties of rice under no nitrogen and nitrogen application showed that nitrogen application increased photosynthesis and respiration rates and nitrogen content of rice plant. However, the increase of photosynthesis rate was not very significant. In comparison, the promotion of leaf respiration by nitrogen application of Ratna, a non aromatic rice, was significantly larger tnan that of HKR228, an aromatic rice variety. Respiration rate and nitrogen content of rice plant dropped remarkably during panicle initiation and heading periods. After heading the nitrogen contents of various parts of rice plant were arranged as follows: blade>panicle>sheath>culm. Basmati 370 had a small culm and a relatively higher plant height. The increase of plant height of this variety by the application of nitrogen was significantly larger than that of the other three varieties. This was one of the major physiological causes difficult for a further increase of the yield of scented rice of Basmati type.