Effect of Nitrogen Stress on Physiological and Biochemical Properties of Different Types of Rice

The compact rice with erect panicles, Shennong 07425, and the loose rice with curved panicles, Akihikari, were used to study the effect of nitrogen applications on thephysiological and biochemical properties of the different types of rice plants.Activities of antioxidant enzymes and damages occurred to thecell membranes of the plants were the criteria used for the evaluation.It was found that MDA inthe leaves of both varieties elevated as the plants aged, and it was more apparent on Akihikari.In addition, either low or high nitrogenlevel resulted in a higher MDA content than those in between.Both varieties, especially Shennong 07425, exhibited a downward trend on CAT and SOD activities with increasingnitrogenapplications.The leaf POD activityrose slightly as theplant grew, reached a peak 15 days after grouting, andended with a gradual decline.The enzymatic activities were more significantly affected by high than low nitrogenlevels.Consequently, it was concluded that a nitrogen fertilization in the range of N 0.1-0.2 g·kg^-1 would enhancethe activities of the protective enzymesin scavenging free radicals delaying senescence of leaves on the plants.Furthermore, theMDA content and POD activity of a rice variety could be used as an indicator in selecting and/or breeding a high-yieldcultivar with an efficient nitrogen utilization capability.