| In order to explore regulating effect of PP333 on yield and quality formation of sweet potato under different nitrogen rate, studies on absorption of nitrogen and potassium elements, nitrogen metabolism, photosynthetic products production, starch formation of Beijing 553 were conducted on the experimental field of Shandong Agricultural University. An experiment included treatment of 0mg.kg-1(M0),100mg.kg-1(M1),200mg.kg-1(M2)respectively under N120kg.hm-2 and N240kg.hm-2. Growth and development and physiological and biochemical research and enzymology were analyzed. The main results were as follows.1 The effect of PP333 on the growth and development of sweet potato under different nitrogen rateUnder the same nitrogen rate, PP333 effectively suppressed the growth of the sweet potato plant, shortened the stem length and internode length, reduced the leaf area index, but increased the specific leaf weight and the stem width and the number of branches per plant. It also reduced the T / R value, increased harvest index.2 The effect of PP333 on yield and yield components of sweet potato under different nitrogen rateUnder the condition of the N120kg.hm-2,The root number after PP333 spraying increased with the concentration increasing, which was no significant difference.While the fresh weight was significantly increased. The yield was the highest in 100 mg.kg-1 concentrations.Under the condition of the N240kg.hm-2.The fresh weight and yield after PP333 spraying were significantly increased. The yield was the highest in 200 mg.kg-1 concentrations.3 The effect of PP333 on the root quality of the sweet potato under different nitrogen rateUnder the same nitrogen rate, the starch content and soluble sugar content of the root under suitable concentration of PP333 spraying were significantly increased. Under the condition of the N120kg.hm-2, PP333 has a small effect on the protein content. Under the condition of the N240kg.hm-2, the protein content was decreased after PP333 spraying.4 The effect of PP333 on N, K elements absorption, and the accumulation of nitrogen metabolism of the sweet potato under different nitrogen rate4.1 The effect of PP333 on N, K elements absorption and the accumulation Under the condition of the N120kg.hm-2, PP333 has a small effect on the nitrogen content and improved the potassium content of the leaves. The nitrogen content of the petiole was significantly were decreased and the potassium content were increased. The nitrogen content of the storage root was increased during the expansion prometaphase, but decreased during the expansion anaphase. The potassium content of the storage root and stem was increased during all sweet potato's life. The nitrogend accumulation and potassium accumulation per plant was increased during all sweet potato's life.Under the condition of the N240kg.hm-2, except the nitrogen content of the leaves, the nitrogen content of the petiole, storage root, stem and the nitrogend accumulation were decreased. The potassium content of all of the organ and potassium accumulation were increased.4.2 The effect of PP333 on nitrogen metabolism characteristics Under the condition of the N120kg.hm-2, PP333 improved the soluble protein content and nitrate reductase activity of the functional blade. GS activity decreased during the expansion prometaphase of root tuber while increased during the expansion anaphasetuber. The soluble protein content increased in big root tuber while decreased in small storage root.The GS activity of big storage root increased during the expansion anaphase tuber while decreased at the harvest.Under the condition of the N240kg.hm-2, the soluble protein content and nitrate reductase activity of the functional blade decreased after PP333 spraying. GS activity increased during the expansion prometaphase.The soluble protein content of the big root tuber and small root tuber were decreased.The GS activity of tuber increased during the expansion anaphase and decreased at the harvest.5 The effect of PP333 on dry matter accumulation and starch formation under different nitrogen rate5.1 Dry matter accumulationUnder the same nitrogen rate, PP333 increased the chlorophyll content of functional leaves, improved the photosynthetic rate and the net assimilation rate and storage root thickening rate of sweet potato, and significantly increased the dry matter accumulation of single plant.5.2 The starch compositions and their content of the root tuberUnder the condition of the N120kg.hm-2, PP333 significantly increased amylose content, amylopectin content and the total starch content of the small root tuber, and had no significant effect on big root tuber. Under the condition of the N240kg.hm-2, PP333 significantly increased amylose content, amylopectin content and the total starch content of the small root tuber and big root tuber.Therefore, PP333 was more beneficial to improve the starch content of the root tube under the N240kg.hm-2. Under the same nitrogen rate, PP333 had a significant effect on starch content of the small root tube.5.3Starch synthaseUnder the condition of the N240kg.hm-2, PP333 increased SS,SSS and ADPGPPase activity, but decreased GBSS activity of the big root tuber 88-108d after planting.Meanwhile, SS,GBSS and ADPGPPase activity of the small root tuber increased and SSS activity decreased.5.4AmylaseUnder the condition of the N120kg.hm-2, PP333 increasedα-amylase andβ-amylase activity of the big root tuber, but decreasedα-amylase andβ-amylase activity of the small root tuber.Under the condition of the N240kg.hm-2, PP333 increasedα-amylase andβ-amylase activity of the big root tuber 88-108d after planting.However PP333 decreasedα-amylase activity of the small root tuber and increasedβ-amylase activity.
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