| At present,the research on Phoebe zhennan mainly focuses on the wood characteristics and growth and cultivation.There are few studies on the leaves of Phoebe zhennan.In this paper,the seasonal variation of leaf morphology and anatomical structure,the seasonal variation of the contents of N,P and K elements,total flavonoids and total polysaccharides in leaves,and the seasonal variation of chemical composition and antioxidant activity of essential oils in leaves of two types of Phoebe zhennan(large-leaf and small-leaf)were systematically studied.The main results are as follows:The morphological characteristics and anatomical structure of leaves of Phoebe zhennan showed an increasing trend with seasonal changes.From spring to autumn,the growth rate is faster,and the indexes in autumn and winter do not change significantly.In the same season,the quantitative indexes of leaf morphological characteristics and anatomical structure of large-leaf were larger than those of small-leaf.The contents of N,P and K in leaves of Phoebe zhennan showed a downward trend with seasonal variation.The contents of N,P and K in leaves ranged from 6.19 g/kg to 12.42 g/kg,3.14 g/kg to 4.41 g/kg and 12.61 g/kg to 18.21 g/kg respectively.There were some differences in the variation range of nutrient elements between the two types of Phoebe zhennan.The contents of nutrient elements in leaves of two types were K > N > P.With the change of season,the total flavonoids content in the leaves of Phoebe zhennan was between 15.01 mg/g and 22.80 mg/g,showing a downward trend,while the total polysaccharides content was between 23.93 mg/g and 50.54 mg/g,showing a first increase and then a downward trend.There was no significant difference in the total flavonoids content between the two types.The total polysaccharides content in the small-leaf was higher than that of large-leaf.The content of N,P,K elements and total flavonoids in different seasons of Phoebe zhennan leaves showed a significant positive correlation,and a significant correlation,and a certain negative correlation with total polysaccharide content,in which P element content and total polysaccharide content had a significant negative correlation.The extraction yield of essential oil from leaves of two leaf types of Phoebe zhennan increased first and then decreased with seasonal variation.The yield of essential oils from large-leaf was 2.27 mL/kg~3.13 mL/kg,and that from small-leaf was 3.27 mL/kg~4.97 mL/kg.In the same season,the extraction rate of essential oil from small-leaf was higher than that of large-leaf.The chemical constituents of the essential oil from the leaves of Phoebe zhennan are mainly aromatic hydrocarbons,alkenes and alcohols.The relative contents of aromatic hydrocarbons,olefins and alcohols in leaf essential oil of large-leaf in different seasons accounted for 25.28%~40.15%,26.87%~51.14% and 17.40%~30.36% of the total components,while the relative contents of aromatic hydrocarbons,olefins and alcohols in leaf essential oil of small-leaf in different seasons accounted for 35.57%~47.53%,34.90%~39.10% and 11.70%~20.77%.In the same season,the species and relative content of essential oil compounds in leaves of two types of Phoebe zhennan differed greatly.The contents of the same compounds in the essential oils of leaves of the same leaf type in different seasons are not significantly different,but the kinds and contents of different compounds are quite different.The essential oil of Phoebe zhennan leaves has certain scavenging ability to DPPH free radicals.In summer and autumn,the DPPH free radical scavenging ability of leaf essential oil of the same leaf type Phoebe zhennan was stronger than that of the large leaf type Phoebe zhennan was weaker in spring,and the DPPH free radical scavenging ability of leaf essential oil of small-leafwas higher than that of large-leaf in the same season. |
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