Elucidating comportment of the glutamate and ornithine pathway on proline accumulation in rice under different nitrogenous nutrition

Proline is a multifunctional amino acid in plant cells known to be involved in growth and development, particularly under various environmental abuses. In this study, the contribution of the glutamate and ornithine pathway on proline accumulation in rice seedlings (Oryza sativa L. cv. XZX 45) under different nitrogenous nutrition was investigated. The main findings include the following: (1) the dynamic changes of free proline pool in studied seedlings parts were highly linked to the nitrogenous species during 48-h exposure, whereas ammonium treatments caused more proline accumulation than nitrate treatments, and the change in free proline in rice seedlings without nitrogen supply was identical to nitrate fertilization; (2) application of external arginine and glutamate caused over accretion of free proline in rice seedlings, amidst them arginine was more efficient than glutamate related to proline synthesis; (3) proline content in both rice tissues is linearly increased with external ammonium applied, while employment of nitrate did not change proline content. The maximum nitrogen fertilization of nitrate and ammonium caused significant decrease of proline in rice tissues when arginine and glutamate were used, and other doses of nitrogen fertilization did not change proline content significantly. Results presented here indicated that the ornithine pathway played notable role in the proline accumulation in rice seedlings than the glutamate pathway under different nitrogenous nutrition.