Volatile components in flowers of 5 rare and endangered orchids
In order to evaluate and screen out valuable aromatic germplasm resources,the flowers of rare and endan-gered orchids,namely,Dendrobium crystallinum,D.moschatum,D.thyrsiflorum,Bulbophyllum phalaenopsis and B.echinolabium were used as materials,and the similarities and differences of volatile components,contents and key aroma compounds were compared between the"fragrant flower"and"smelly flower".Solid-phase microextraction ar-row combined with gas chromatography-mass spectrometry(SPME Arrow-GC-MS)and relative odor activity(rOAV)were used for identification and analysis.A total of 675 volatile compounds were identified,including terpenoids,heterocyclic compound,esters,hydrocarbons,ketones,alcohols,aldehydes and aromaticity.Terpenoids were the highest in relative content and the most abundant in volatile substances,followed by heterocyclic compound and es-ters.The volatile components of the five rare and endangered orchids were species-specific,yet terpenoids,heterocy-clic compound,esters,hydrocarbons,ketones,alcohols and aldehydes were the major constituents,which accounted for more than 90％in total.The quantity of volatile components in the flowers of the five orchids decreased in the or-der of D.crystallinum＞D.moschatum＞B.echinolabium＞B.phalaenopsis＞D.thyrsiflorum.There were 104,87,72,90 and 77 key aroma compounds in the flowers of D.crystallinum,D.moschatum,D.thyrsiflorum,B.phalae-nopsis and B.echinolabium,respectively,Aldehydes were the main contributors to the overall aroma of orchids.Di-ethyl disulfide compounds and dimethyl trisulfur compounds in B.phalaenopsis,and indole,3-methyl and dimethyl trisulfide in B.echinolabium were the main contributors for their unique odor formation.The volatile components of the 5 species of orchids were valuable for resource utilization.The volatile components in the flowers of D.crystalli-num and D.moschatum might contain cyclamen aldehyde.
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