Study On The Nutritional Effect And Mechanism Of Pepper Under The Supply Of Amino Acid Nitrogen And Inorganic Nitrogen

Plants can directly absorb inorganic nitrogen and amino acid nitrogen from the outside world.When amino acid nitrogen partially replaces inorganic nitrogen,it is beneficial to promote plant growth and nutrient absorption,and improve plant quality.In this paper under the condition of equal nitrogen,aspartic acid and glutamic acid were used to replace inorganic nitrogen at 10%,20%,30%,40%and 50%for the pepper（Zunla NO.9）pot experiments.Based on the isotope tracer technique,¹⁵N-labeled aspartic acid and ¹⁵N-labeled glutamic acid were applied to study the nitrogen contribution of amino acid nitrogen to pepper under different substitution ratios in the solution culture experiment.At the same time,the effects of amino acid nitrogen on pepper growth,nitrogen metabolism,fruit quality and capsaicin synthesis under different substitution ratios were investigated in the sand culture experiment.The main conclusions of this paper are as follows:（1）The contribution of different substitution ratios of amino acid nitrogen to pepper nitrogen nutrition was different.The results of ¹⁵N tracer analysis showed that with the increase of the substitution ratio of aspartic acid or glutamic acid,the contribution rate of aspartic acid nitrogen(NDff _Asp-N),the contribution rate of glutamic acid nitrogen(NDff _Glu-N),the absorption of ¹⁵N and the distribution rate of¹⁵N in the shoots and roots of pepper increased continuously,with the maximum at50%amino acid substitution ratio,which was 4.64 times and 4.69 times higher than that of NDff _Asp-Nand NDff _Glu-Nin the whole plant of pepper treated with 10%amino acid,respectively.The absorption of ¹⁵N in aspartic acid treatment was higher than that in glutamic acid treatment.（2）Amino acid nitrogen can promote the growth,nutrient accumulation and dry matter increase of pepper plants by replacing inorganic nitrogen with appropriate proportion.At the harvest stage（150d）,the whole plant dry matter weight of pepper treated with aspartic acid or glutamic acid substitution increased by 3.55%～27.05%and 1.72%～28.88%,respectively,compared with inorganic nitrogen treatment.The20%amino acid substitution ratio was beneficial to the increase of plant height,stem diameter,total root length,root surface area,root volume and the accumulation of nitrogen,phosphorus,potassium and dry matter.Among them,aspartic acid significantly increased the plant height of pepper,and glutamic acid was beneficial to the increase of total root length,root surface area and root volume of pepper.（3）Partial substitution of inorganic nitrogen by amino acid nitrogen could increase the activity of nitrogen metabolism enzymes in pepper leaves.The replacement of inorganic nitrogen by 20%aspartic acid or glutamic acid was beneficial to the increase of GOT,GPT and GS activities in pepper leaves.The activities of GOT,GPT and GS were 101.59 umol·g^-1·h^-1,29.55 umol·g^-1·h^-1,1.07A·mg^-1·h^-1under 20%aspartic acid treatment,and 90.56 umol·g^-1·h^-1,29.99 umol·g^-1·h^-1,1.30 A·mg^-1·h^-1under 20%glutamic acid treatment,respectively.Glutamate is beneficial to the increase of GS activity.（4）Partial substitution of amino acid nitrogen for inorganic nitrogen can improve pepper quality and promote capsaicin synthesis.When 20%aspartic acid or glutamic acid partially replaced inorganic nitrogen,the content of soluble sugar,soluble protein,vitamin C and the yield per plant of pepper were significantly increased,and the nitrate content of pepper was significantly reduced.At the same time,the activity of phenylalanine ammonia lyase,capsaicin synthase and capsaicin synthesis intermediate were significantly increased,which ultimately promoted the accumulation of capsaicin.The content of capsaicin in placenta treated with 20%aspartic acid/glutamic acid was 19.80 mg/g DW and 19.04 mg/g DW,respectively.Aspartic acid can promote the improvement of pepper yield and quality more than glutamic acid,while amino acid types have little effect on capsaicin synthesis.In summary,pepper can utilize amino acid nitrogen.Amino acid nitrogen contributes the most to nitrogen nutrition of pepper under 50%aspartic acid or glutamic acid substitution ratio,but 20%amino acid substitution ratio is the most suitable ratio for pepper growth,nitrogen metabolism and capsaicin synthesis.The above research results can provide theoretical support and scientific basis for amino acid nitrogen formula fertilization to improve spicy quality.