Study On The Development Of Litsea Cubeba Fruit And The Change Of Its Essential Oil

Litsea cubeba is a kind of Cinnamomum,deciduous shrub or small tree.It has many advantages,such as large biomass,strong adaptability,fast-growing and barren tolerance.It is an important spice and oil resource plant in South China.The fruit,flower,leaf and root of Litsea cubeba can be used as raw materials to extract Litsea cubeba essential oil,and the content of essential oil in fruit is the highest.Citral is the main component of Litsea cubeba essential oil,with the content up to 70%.It is an important raw material used to make ionone series spices.Citral is widely used in food,pesticide,medicine,cosmetics,washing and many other fields.At present,the development and utilization of Litsea cubeba is still in the stage of using wild resources,and there are few reports.In this study,Litsea cubeba was used as the research object.By means of field investigation,microscopic observation,physiological and biochemical determination and gas chromatography-mass spectrometry,the morphological structure changes,oil drop changes in tissue cells and the accumulation characteristics of essential oil components of Litsea cubeba fruit in the whole development stage were studied.The photosynthetic efficiency related parameters of the plant were measured and analyzed In order to improve the utilization efficiency of Litsea cubeba fruit and determine the best harvest time.The results are as follows:1.Fruit Morphological Development and essential oil changeThe fruit development of Litsea cubeba can be roughly divided into three periods:rapid growth period,slow growth period and fruit color change period.In the period of rapid growth,the volume of fruit increases rapidly,while the accumulation of essential oil is relatively slow;in the period of slow growth,the volume growth rate of fruit decreases,while the accumulation of essential oil is rapid;in the period of fruit color change,the fruit develops gradually and matures,and the skin color becomes darker in the later period.In the process of fruit development,the water content gradually decreased and the content of essential oil gradually increased.In August,the content of essential oil reached the highest value of 4.96%.There was a significant positive correlation between the content of essential oil and the 1000 grain weight of fruit.2.Changes of fruit contentsThe change trend of starch and soluble sugar was similar,which showed a downward trend in the fast growth period of fruit,and the lowest value(soluble sugar content:8.91 mg·g-1;starch content:7.97 mg·g-1)appeared at 33d after anthesis.After entering the slow growth period,the content began to rise,gradually reached the level of the early development stage,and after entering the fruit color change period,the content decreased again.The protein content was rapid in the fruit During the growth period,the protein content increased rapidly,reaching 26.24 mg·g-1 at the maximum.The peak concentration was about 2 times of that at the early stage of development.After the fruit color changed,the content decreased rapidly.According to the correlation analysis,soluble sugar and starch have no significant correlation with the changes of fruit external morphology and the accumulation of essential oil,while protein content has correlation,but it is still not significant.In the second rapid growth period of fruit,the content of soluble sugar and starch slightly decreased but not obvious,while the content of protein is rapidly decreased,which is the period of rapid increase of fruit essential oil content,It may be that protein is transformed into oil in large quantity.3.Changes of oil droplets in fruit cellsIn May,there were a few oil droplets in the fruit cells.With the development of the fruit,the number of oil droplets increased rapidly,the volume increased rapidly,the shape of oil droplets became round,and gradually spread from the nucleus and cell membrane to the cytoplasm.4.Changes of photosynthetic efficiency of Litsea cubebaFrom May to August,the net photosynthetic rate,transpiration rate,stomatal conductance and intercellular CO2 concentration of Litsea cubeba were measured.It was found that there was "noon break" in the change of net photosynthetic rate,among which the average daily change of net photosynthetic rate in May was 10.84 ?mol·m-2·S-1,the lowest in May to August,the average daily change of net photosynthetic rate in June to August was similar,and the highest in June,The daily change of transpiration rate showed a continuous upward trend from May to August,with the lowest value of 6.56 mmol·m-2·s-1 in May and the highest value of 8.31 mmol·m-2·s-1 in August.The stomatal conductance did not change significantly from May to August,and kept a level of about 0.4?mol·m-2·s-1,with the lowest value of 0.377 ?mol·m-2·s-1 in May and the highest value of 0.424 ?mol·m-2·s-1 in August:in the change of intercellular CO2 concentration,the CO2 concentration of Litsea cubeba is higher in the morning and evening of a day,and there will be obvious valley value in the afternoon.The average value of intercellular CO2 does not change significantly in the middle of May August,the lowest value is 269 ?mol·mol-1 in May,and the highest value is 278.3 ?mol·mol-1 in June.In conclusion,the four indexes in May are the lowest,and the net photosynthetic rate,transpiration rate and stomatal conductance in June,July and August are the lowest Degree and intercellular CO2 concentration were almost the same,which indicated that photosynthesis of Litsea cubeba kept high efficiency in other months except may.5.Changes of main components of essential oil during Fruit DevelopmentThe essential oil of Litsea cubeba fruit in different development stages was analyzed by gas chromatography.The results showed that there were 20 components in the essential oil from May to September,among which 19,20,20,1 7 and 16 were detected respectively from May to September,and there were 15 components in the essential oil from May to September.The main components of the essential oil were:d-limonene,eucalyptus oil alcohol,verbenol,citral and vanillin.With the development of fruit,the content of d-limonene and Eucalyptus oleanol decreased significantly.The content of d-limonene reached 39.92%in May,2.31%in September,11.40%in May,0.73%in September.The content of citral(citral+vanillin)increased significantly.In May,the content of citral was 12.05%,and the content of vanillin was 17.44%.In September,the content of citral increased To 31.14%,the content of vanillin increased to 40.49%,while the content of verbenol did not change regularly,and remained relatively stable.Although the citral content in September is slightly higher than that in August,the optimum harvest time of Litsea cubeba fruit can be determined as the last ten days of August due to the obvious decrease of essential oil content in September.The contents of d-limonene,Eucalyptus 1.98%,verbenol 7.41%,citral 25.56%and vanillin 31.82%,respectively.There was significant correlation between the content of citral and the content of essential oil.