| During the process of heartwood formation,a series of physiological and biochemical changes occur in the trees,resulting in changes in the chemical composition of the heartwood.In order to clarify the chemical composition variation of sapwood-transitional wood-heartwood and its relationship with the formation of heartwood,this paper uses Dalbergia odorifera as the research object.The variation of the chemical composition of the extract was analyzed by gas chromatography-mass spectrometry(GC-MS),ultra-high performance liquid chromatography-mass spectrometry(UPLC-MS)and time-of-flight secondary ion mass spectrometry(TOF-SIMS).The variation of lignin was analyzed by Fourier transform infrared spectrometry(FTIR)and ultraviolet-visible spectrophotometry(UV),and the variation of mineral elements were analyzed by the atomic absorption spectrophotometer.The main conclusions are as follows:(1)There were differences in the chemical composition of three different regions of the sapwood,transition wood and heartwood.The content of extractions in heartwood was 6.4% and 9.31% higher than that of transition wood and sapwood respectively,the content of lignin is 4.77% and 5.65%respectively,and the content of ash was 0.72% and 0.77%.The highest content of extraction and lignin was the result of the continuous accumulation of characteristic components of the heartwood in the process of heartwood and the continuous lignification of cells in the process of heartwood.The above chemical compositions were very close to each other in the transition and sapwood,and were only 1/10 th of the content of the heartwood,indicating that the changes in these compositions during the formation of the heartwood occur mainly at the junction of the transition and heartwood.(2)There was an overall increase in the content of the flavonoids and volatile oils from the bark towards the pith.The radial variation law of the five heartwood components of T-Nerolidol,isoliquiritigenin,naringenin,daerlin,andformononetin was consistent,with a tendency to increase from the bark to the pith,and 10-150 times higher in the darker part of the 4th growth ring.For example,naringenin,the darker part and lighter colored part of the fourth growth ring were 0.61 mg / g and 0.0044 mg / g,respectively,which were about140 times higher.Macrostructural pictures showed that the darker part of the fourth growth ring was the junction of the transitional wood and the heartwood,indicating that these heartwood components were heavily synthesized at the junction of the transition material and the heartwood.(3)The lignin of Dalbergia odorifera ground wood gradually deepens in color from the bark toward the pith.The lignin color of the 10 th to 5th growth ring and the lighter part of the 4th growth ring was a cheese color,and from the darker part of the 4th growth ring the lignin color began to darken due to the more benzene ring and conjugated C==O group structure.The color of ground lignin began to change significantly in the darker parts of the fourth growth ring,indicating that the change of lignin also occurred primarily at the junction of transition wood and heartwood.(4)There are three main types of radial variation of Dalbergia odorifera mineral elements.The concentration of K element gradually decreased from the bark to the pith,Ca and Mg elements were opposite,while the concentration of Na element increased first and then decreased.However,the concentration of these elements were significantly changed in the darker part of the fourth growth ring,indicating that the elemental concentration changes at the junction of the heartwood and the transition wood were closely related to the formation of the heart material.This study clarified the chemical composition variation of sapwood-transition wood-heartwood of Dalbergia odorifera,and illustrated that the composition of heartwood was generated at the junction of heartwood and transitional wood,which would provide a scientific basis for artificially regulating heartwood formation of Dalbergia odorifera. |
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