Effects of Neodymium on the Activity of the Nitrogen Metabolism Related Enzyme in Seedless Watermelon Leaves

Purpose In order to provide theoretical basis of the appropriate application of Nd³⁺, the effects of different concentrations of Nd³⁺ on the nitrogen metabolism of leaves in seedless watermelon were analyzed, and the interrelationships between the contents of the total nitrogen and the activities of the metabolism related enzymes were also probed.Method On the foliage of seedless watermelon at straw period, incipient blooming period and fruit expansion period were sprayed with 0,5,10,25,50,100 mg/L Nd³⁺ solution, the contents of the nitrogen and the soluble protein, and the activities of nitrate reductase(NR), glutamine synthase(GS) and glutamate dehydrogenase(GDH) were determined.Results (1) Treating with 10 mg/L Nd³⁺ solution had the most significant effect among all treatments, while the contents of the nitrogen and the soluble protein, and the activities of NR, GS and GDH of leaves were all the highest and extremely significantly higher than CK. (2) In the fruit expansion period, the values of the treatment with 10 mg/L Nd³⁺ solution were all extremely significantly lower than CK, which meant that treating with the high concentration of Nd³⁺ solution would inhibit the activities of the metabolism related enzymes in the later period. (3) Correlation analysis showed that the contents of the total nitrogen of leaves all had extremely significant positive correlations with the activity of NR, GS and GDH.Conclusion According to the comprehensive nitrogen metabolism related indicators, 10 mg/L Nd³⁺ would be considered as the suitable concentration for seedless watermelon on the production.