Responses of Growth, Enzyme Activity, and Flower Bud Differentiation of Pepper Seedlings to Nitrogen Concentration at Different Growth Stages

Abstract

The concentration of nitrogen fertilizer is matched with the nutrient requirements in different growth stages of plants, which coordinates their vegetative and reproductive growth. In this study, the influences of nitrogen concentration before and after initiation of flower bud differentiation (first and second stage, respectively) on pepper seedling quality were studied. The chlorophyll a content, sucrose synthase activity, and sucrose phosphate synthase activity of pepper seedlings grown under moderate nitrogen (15 mmol L−1) in the first stage combined with high nitrogen (25.61 mmol L−1) in the second stage were 15.7%, 39.3%, and 34.6% higher than those of the same nitrogen concentration (15 mmol L−1) in the first and second stages treatment, respectively. The regression model also showed that the values of flower bud diameter, shoot fresh weight, root fresh weight, and glutamine synthetase activity of pepper were high under the condition of moderate nitrogen in the first stage and higher nitrogen in the second stage. In addition, the results of comprehensive evaluation showed that moderate nitrogen (15 mmol L−1) in the first stage and high nitrogen (25.61 mmol L−1) in the second stage treatment ranked first, which improved carbon and nitrogen metabolism, increased biomass accumulation, and promoted the flower bud differentiation and flowering of pepper seedlings.