柑橘果皮油胞发育与精油积累的相关性及品种差异OA

[Objective]Citrus essential oils are commercially valuable secondary metabolites synthe-sized and stored in specialized secretory structures called oil glands within the fruit flavedo.The accu-mulation patterns of these oils show considerable diversity among citrus species,but the underlying reg-ulatory mechanisms connecting gland development with oil deposition remain inadequately character-ized.This research aimed to systematically investigate the relationship between oil gland morphogene-sis and essential oil accumulation by examining three representative citrus cultivars:Gaoban pummelo(Citrus grandis),Hamlin sweet orange(C.sinensis),and Ponkan mandarin(C.reticulata).Through comprehensive analysis of the developmental dynamics of oil glands and their correlation with essential oil content,this study sought to provide crucial insights into the species-specific regulation of essential oil accumulation and establish a theoretical foundation for targeted genetic improvement of citrus germ-plasm.[Methods]The study employed a systematic approach to analyze oil gland development and es-sential oil accumulation patterns.Fruits were sampled at seven developmental stages:50,90,120,150,180,210,and 240 days after flowering(DAF).For morphological analysis,we integrated fruit mor-phometry with advanced microscopic imaging techniques.High-resolution images of peel surfaces were captured using stereomicroscopy and processed with ImageJ software for quantitative assessment of oil gland number,density and volume.Total oil gland number per fruit was determined by direct counting,while density was calculated as glands per unit area.Individual gland volumes were estimated from cross-sectional measurements using geometric models.Essential oil content was quantified through standardized solvent extraction with n-hexane,followed by volumetric measurement of the extracted oil.Statistical analysis included Pearson correlation to evaluate relationships between morphological pa-rameters and oil content.[Results]The investigation revealed distinct patterns in oil gland develop-ment across the three cultivars.All of the species showed a rapid increase in total oil gland number dur-ing early developmental stages(50-150 DAF),followed by stabilization as the fruits approached maturi-ty.This pattern indicated that oil gland initiation is primarily confined to the first half of fruit develop-ment.In contrast,oil gland density demonstrated a consistent decline throughout development in all cul-tivars,reflecting the diluting effect of fruit surface expansion.Volumetric development displayed signifi-cant interspecific variation.Gaoban pummelo exhibited progressive volume increase throughout devel-opment,with glands expanding continuously from 50 DAF until maturity.Hamlin sweet orange showed delayed volumetric growth,maintaining minimal size increase until 120 DAF followed by active expan-sion thereafter.Technical constraints prevented reliable volume measurement in Ponkan mandarin due to its irregular peel morphology.Essential oil accumulation patterns correlated with gland development strategies.Gaoban pummelo displayed rapid oil accumulation after 180 DAF,coinciding with its pro-gressive gland expansion.Hamlin sweet orange entered rapid accumulation phase earlier,from 90 DAF onward,while Ponkan mandarin initiated substantial accumulation after 150 DAF.Correlation analysis identified species-specific determinants of oil content.In Gaoban pummelo,oil gland volume showed the strongest correlation with essential oil content,indicating a volume-dominant strategy.Hamlin sweet orange demonstrated stronger dependence on oil gland number,suggesting a number-dominant approach.Ponkan mandarin showed weaker correlation with gland number,implying involvement of ad-ditional regulatory factors beyond those measured.[Conclusion]This study demonstrated that citrus va-rieties employ distinct oil gland development strategies to regulate essential oil accumulation.The rela-tionship between gland morphology and oil content is conserved across varieties,but the relative impor-tance of different morphological parameters varied significantly.Gaoban pummelo utilizes continuous gland expansion to enhance storage capacity,while Hamlin sweet orange relies more on maintaining nu-merous glands.Ponkan mandarin appears to employ an alternative strategy that may involve additional physiological or biochemical regulation.These findings highlight the diversity of essential oil accumula-tion mechanisms in citrus and provide valuable insights for future research on metabolic regulation in oil glands.The identification of varieties-specific strategies offers practical guidance for breeding pro-grams aimed at modifying essential oil characteristics in different citrus types.