Effects Of Foliar-applied Four Trace Elements On The Photosynthetic Characteristics,Yield And Quality Of Paeonia Ostii ‘Fengdan’

Oil peony is an emerging woody oil crop.In recent years,the planting area of oil peony has been continuously expanded in China.However,little research has been done on the cultivation of oil peony.In this study,Paeonia ostii‘FengDan’was used as the experimental material.We explored the effects of foliar spraying of iron,molybdenum,boron and zinc on photosynthetic characteristics,yield and seed oil quality of oil peony in order to provide a theoretical basis for rational,high-yield oil cultivation and fertilization techniques.The main findings are as follows:1.The results of spraying iron fertilizer test showed that the foliar application of iron fertilizer could effectively change the average daily net photosynthetic rate（Pn）and stomatal conductance（Gs）of’Fengdan’,and Pn was the highest in 0.8%iron fertilizer treatment,which was 16.11%higher than that of the control group.and increased the accumulation of photosynthetic products.Through the model-fitting analysis of the light response curve and CO₂ response curve,it was concluded that the appropriate concentration of iron fertilizer could significantly increase the Pnmax and Amax value of’Fengdan’,which characterize the potential photosynthetic capacity,the maximum value can reach 12.98μmol·m^-2·s^-1 and 33.51μmol·m^-2·s^-1respectively.At the same time,the apparent quantum efficiency（AQY）,initial carboxylation efficiency（ACE）,light saturation point（LSP）and CO₂ saturation point（CSP）of‘Fengdan’were also significantly affected,and suitable concentration application enables‘Fengdan’to adapt to a wider range of light intensity and CO₂concentration.The chlorophyll content（Chl）of leaves was significantly changed by iron application,the value of Chl a+b at 0.8%iron fertilizer’s concentration increased significantly,reaching 2.70 mg g^-1.Different concentrations of iron fertilizer affected the yield of Fengdan by affecting agronomic traits.Grain yield increased when the iron fertilizer’s concentration was 0.8%,which was 16.80%higher than that of the control group.The results of GC-MS analysis showed that the content of unsaturated fatty acids of‘Fengdan’was increased by applying appropriate concentration of iron fertilizer,and the nutritional value of‘Fengdan’seed oil was increased to a certain extent.All the above results showed that 0.8%ferrous sulfate had the best effect.2.The results of spraying molybdenum fertilizer showed that with the increase of molybdenum fertilizer concentration,the Pn,Gs and Tr values all increased first and then decreased.The treatment group with 0.08%molybdenum fertilizer concentration had the highest Pn value,which was 19.27%higher than that of the control group.The results of light response curve and CO₂ response curve fitting show that the appropriate concentration of molybdenum fertilizer could increase the Pnmax and Amax value of’Fengdan’,which characterize the potential photosynthetic capacity,the maximum value can reach 14.52μmol·m^-2·s^-11 and 33.47μmol·m^-2·s^-1respectively.At the same time,its AQY,ACE,LSP and CSP values were also affected to varying degrees.The chlorophyll content（Chl）of leaves was significantly changed by molybdenum application,the value of Chl a+b at 0.8%molybdenum fertilizer concentration increased significantly,reaching 2.772 mg g^-1.Different concentrations of molybdenum fertilizer treatment had significant effects on the agronomic traits and yield of’Fengdan’,and the grain yield increased when molybdenum fertilizer concentration was 0.08%,which was 19.42%higher than that of the control group.The analysis results of GC/MS showed that the application of molybdenum fertilizer had little effect on oleic acid but had a significant effect on linolenic acid.Pearson correlation analysis showed that stearic acid and linolenic acid,oleic acid and linoleic acid were significantly negatively correlated（P<0.01）.3.The results of spraying zinc fertilizer showed that with the increase of zinc fertilizer concentration,the Pn,Gs and Tr values all increased first and then decreased.,and Pn was the highest in 1.5%zinc fertilizer treatment,which was14.88%higher than that of the control group.The results of light response curve and CO₂ response curve fitting show that the appropriate concentration of zinc fertilizer could significantly increase the Pnmax and Amax values of’Fengdan’,which characterize the potential photosynthetic capacity,the maximum value can reach14.12μmol·m^-2·s^-11 and 37.67μmol·m^-2·s^-1 respectively.At the same time,the AQY and ACE values of‘Fengdan’were also significantly affected.The chlorophyll content（Chl）of leaves was significantly changed by zinc application,the value of Chl a+b at 1.5%zinc fertilizer concentration increased significantly,reaching 2.67 mg g^-1.Zinc fertilizer treatment significantly changed the yield of‘Fengdan’,and the grain yield increased when the concentration of zinc fertilizer was 1.5%,which was 19.49%higher than that of the control group.The analysis results of GC/MS showed that zinc application had a significant effect on the content of five major fatty acids,especially linolenic acid.Pearson correlation analysis showed that oleic acid and linolenic acid were significantly negatively correlated（P<0.01）.4.The results of spraying test of boron fertilizer and zinc fertilizer showed that The average daily net photosynthetic rate（Pn）of single application of boron fertilizer,zinc fertilizer and combined application of boron and zinc was 16.46%,19.35%and37.43%higher than that of control group,respectively,which increased the accumulation of photosynthetic products of‘Fengdan’.The fitting of light response curve and CO₂ response curve showed that spraying boron fertilizer and zinc fertilizer could significantly increase the Pnmax and Amax value of’Fengdan’,which characterize the potential photosynthetic capacity,and also increased the AQY,ACE,LSP and CSP values of‘Fengdan’.The application of boron and zinc increased the Chla/Chlb value of leaves of Fengdan,and had a great influence on the contents of nitrogen,phosphorus,iron,manganese,boron and zinc in leaves.The application of boron alone,single application of zinc and boron and zinc resulted in higher Fengdan’s grain yields of 11.93%,10.04%and 25.08%respectively than that of the control group.The analysis results of GC/MS showed that different fertilization treatment had little effect on oleic acid but had significant effect on linoleic acid.All the above results showed that the effect of combined application of boron and zinc fertilizer was the best.