Effects of environmental stress on the relationship of free amino‐N to fresh weight of rice plants

Abstract

A study was made on the effects of light and temperature combinations, nitrogen (N) carriers, and N levels on the growth and free amino‐N pool size of rice plants. The experiment was conducted in a growth chamber in nutrient solution. Combinations of high light supply (40,000 lux), or high temperature (35°C), or both, resulted in accumulation of large amino‐N pools. There were negative relationships between free amino‐N pool sizes and the fresh weight of plants. These negative relationships could be best described by decay curves. On the other hand, in plants under the low light (17,280 lux) and low temperature (24°C) combination, the amino‐N to fresh weight relationship was positive, and fitted to a straight line. The amino‐N to free sugars relationship fitted decay curves, irrespective of light and temperature combinations. The ammonium‐N to amino‐N relationship under high light and/or high temperature combinations showed a quadratic response. Analysis of these curves suggests that deamination takes place as free NH₄‐N increases in plants. The results show a strong effect of the free sugar pools on the N‐metabolism of plants under stress. We suggest the decay type curves are a characteristic of the amino‐N versus fresh weight relationships of plants under environmental stress.