Effect Of Different Agronomic Measures On Carbon-Nitrogen Metabolism And Oil Accumulation In Rapeseed Pod

Oil content in seeds is not only controlled by multiple genes,but also affected by non-genetic factors such as environment and cultivation measures.In this experiment,different varieties were used to study the relationship between the growth and decline of carbon and nitrogen and the accumulation of oil in rapeseed pods by setting different sowing date,density and fertilization.Ten rapeseed varieties with different oil content were used in the experiment.Four sowing dates,five densities,seven nitrogen levels,and different combinations of chemical nitrogen,phosphorus,potassium and organic fertilizers were set.Physiological indices of oil content,protein content,pod biomass,soluble sugar content in seeds and pericarps,total nitrogen content and chlorophyll content in rapeseed at different stages of pod development were systematically determined.The results are as follows:1.Developmental regularity of pod in rapeseedWithin 20-50 days after flowering,the dry matter weight per pod increased continuously,and the range of variation was 0.013-0.119 g under different cultivars and cultivation conditions.Within 20-35 days after flowering,the dry matter weight per pod increased gradually,and then decreased gradually.The ratio of seed to shell was positively correlated with oil content in the same variety.2 Basic Rules of Carbon and Nitrogen Metabolism in Rapeseed(1)Soluble sugar content of podA trend of increasing first and thendecreasing was showed on the soluble sugar content in seeds.Generally,the highest value was appeared at 20-30 days after flower reaching 15-28%,then the soluble sugar content quickly dropped below 10%,and not more than 5%untill harvest.The soluble sugar content in pod wall was higher than that of seeds at 20-25 days after flower with the highest content 15-38%,it decreased to less than10%after 30-40 days(the actual date is greatly affected by climatic conditions),and not more than 5%untill harvest.During the 20th to 25th day of pod growth,the soluble sugar content in seeds ranged from 10%to 20%and in pod wall from 15%to 30%.The higher content likely to contribute to fat accumulation.The sugar content in high oil content varieties was relatively high.However,the soluble sugar content of pod exceeds 35%may mean to meet stresses?(2)Total nitrogen content of podTotal nitrogen content of seeds increased or tended to be stable with the development of seeds.The maximum total nitrogen content in seeds of different varieties and cultivation measures appeared at maturity,range from 2.46%to 5.39%.The total nitrogen content in pod wall showed a trend of first high and then low,the maximum value appeared at 20-25 days after flower ranged from 1.49 to 3.07%,and thendecreased to0.64-1.95%at maturity.(3)Carbon-nitrogen ratio of podThe C/N ratio of seeds was first high and then low with pod development.Underdifferent varieties and cultivation measures,the maximum value of pod seeds was3.8-9.13 in 20-25 days after flower and rapidly decreased to less than 3 after 30th day.The C/N value of pod wall was the highest at 20-25 days after flower,ranging from 12.52to 35.60,which was much higher than the C/N value of seeds.The C/N value of seeds and pod wall of strong plants with high oil content should be 5-8 and 10-15 at 20-25 days after flower,and thendecrease rapidly.3.Accumulation and Change of Oil and Protein in seedsDuring the 25-50 days of pod development,the oil content of different varieties increased from 5%to about 50%.The seed protein content can reach 15-25%at 20-25days after flowering and 20-30%at maturity.The average daily temperature of pod stage is 16-20?.Increasing density properly,reducing nitrogen and topdressing,increasing phosphorus and potassium fertilizers are conducive to increasing oil content.4.Different sowing dates are mainly due to the difference of temperature during pod stage,which results in different oil content.Different sowing dates affect the process of oil accumulation because of the difference of temperature caused by different maturity time.Among the four sowing dates from September 15 to October 30,the suitable daily average temperatures of early-maturing variety Hunan 1358,Mid-late-maturing variety Zhongshuang 11 and late-maturing variety Zheshuang 8 for obtaining high oil content of pod were 17.7,17.9and 18.9?,respectively,and the suitable accumulated temperatures were 887,895 and946?,respectively.5.Suitable planting density can coordinate light and nitrogen level to increase oil content.In the range of 15-75*10~4/ha density,the final oil content of seeds with medium and low density(45-60*10~4/ha)was the highest.Under the medium density of 75*10~4/ha,the nitrogen level of a single plant was lower than that of a sparse plant,and the soluble sugar content,maximum chlorophyll content and C/N of seeds and pericarps maintained a higher level at 25 days after flowering.6.Effects of inorganic nitrogen,phosphorus,potassium fertilizer and organic cake fertilizer on oil accumulationThe inorganic nitrogen,phosphorus and potassium combined application was beneficial to the accumulation of oil content,which was 2.5,3.0 and 3.8%higher than the treatment of phosphorus,potassium and phosphorus deficiency,respectively.On the basis of the same application amount of N,P and K,increasing cake fertilizer(100kg/667m2)reduced oil content of mature seeds by 2.9%.The difference of soluble sugar content in pericarp and seed was the greatest in 20-30 days after flowering.The highest soluble sugar content in pericarp and seed was 22.4%and 22.7%in nitrogen deficiency treatment,and the highest C/N value was 17.2 and 10.1,respectively.Compared with P deficiency treatment,P deficiency treatment significantly reduced the soluble sugar content in pericarp and seed by 13.2%and 4.4%respectively,and C/N values by 12.8 and 2.2,respectively.Potassium deficiency reduced the soluble sugar content of pericarp and seed by 6.8%and 6.3%,respectively,while C/N decreased by 9.1 and 3.2.7.Effects of different nitrogen application rates and modes on oil accumulation(1)Suitable nitrogen application is beneficial to oil accumulation.Extreme nitrogen deficiency affects the normal physiological metabolism of plants,and the oil content will decrease.Increasing the amount of nitrogen fertilizer in the range of N5-N25 shows that the oil content of seeds decreases.The duration of higher soluble sugar content in Pericarp of Zhongyou 36 with high oil content was longer than that of Huayou Za 9 with medium oil content.The soluble sugar content and C/N value of seeds and pericarps at different nitrogen levels were significantly different at the early stage of seed development.The soluble sugar content and C/N in pericarp decreased with the increase of nitrogen application.The effects of different nitrogen application rates on soluble sugar content and C/N in pericarp were greater than that in seed.(2)Effects of different basal and topdressing methods of nitrogen fertilizer on oil accumulation.Under the same topdressing level of 10 kg/667 m2 and 0.5-10 kg/667 m2of base fertilizer application,the oil content of seeds decreased with the increase of base fertilizer application,and the highest was N10.5-N12.5 of base fertilizer application.The seed yield and protein content per plant increased with the increase of base fertilizer application,respectively,in N20 treatment.Maximum.Under the same total fertilizer application,the oil content of seed decreased with the increase of topdressing times.The highest oil content was 40.49%in all base fertilizer treatments.Compared with the whole basal fertilizer treatment,the oil content of seeds decreased by 1.58%and 2.31%respectively in one and four topdressing treatments.However,seed yield and protein content increased,and the highest yield was obtained by four topdressing treatments.8.Correlation Analysis of Oil Content and Indicators in Seeds(1)Effect of sowing date on oil contentThe soluble sugar content in seeds,total nitrogen content in seeds,soluble sugar content in pericarp and C/N content in pericarp were negatively correlated with oil content in mature seeds 25 days after flowering,with correlation coefficients of 0.81,0.83,0.67 and 0.60,respectively.The chlorophyll content in seeds and pericarps was negatively correlated with oil content in mature seeds 45-50 days after flowering,and the correlation coefficient was above 0.9.(2)Effect of Nitrogen Level on Oil ContentOil content in mature seeds was positively or significantly correlated with soluble sugar content in seeds and pericarps at the early stage of pod development.Zhongyou 36still had high soluble sugar content for oil synthesis 40 days after flowering.The oil content of mature seeds was negatively correlated with the total nitrogen content of seeds and pericarps at the later stage of pod development,and positively correlated with C/N of seeds and pericarps at the whole seed filling stage.The correlation coefficient was above0.6,and above 0.7 with C/N of pericarps.C/N in pericarp is more correlated with oil content,which may be a key index for predicting oil content.9.Agronomic Measures for Increasing Oil ContentFirst of all,we should select the good varieties with high oil content suitable for cultivation in this area.Zhongyou 36,high oil hybrid lines,Zheshuang 8 and Zhongshuang 11 all show high oil content traits(45-53%)in the middle and lower reaches of the Yangtze River.Secondly,we should adopt reasonable and effective cultivation measures suitable for this variety.Early and middle maturity varieties can be sown late and late maturity varieties can be sown early,which will not affect the oil content of rapeseed,but also ease the problem of stubble tension.Under medium density conditions,the population had good ventilation and light transmission,and individual plant carbon and nitrogen metabolism was coordinated,which was more conducive to the accumulation of oil content in rapeseed.Increasing the application rate of P and K fertilizer was beneficial to the accumulation of rapeseed oil.When the soil fertility is too low,appropriate application of nitrogen fertilizer can increase the oil content of rapeseed;when the soil fertility is high,appropriate reduction of nitrogen fertilizer application is an effective cultivation measure to coordinate the quality and yield of rapeseed without significantly reducing the yield.