Species-specific regulatory pathways of small RNAs play sophisticated roles in flower development in Dimocarpus longan Lour.

Flower development plays vital role in horticultural plants.Post-transcriptional regulation via small RNAs is important for plant flower development.To uncover post-transcriptional regulatory networks during the flower development in Dimocarpus longan Lour.‘Shixia’,an economically important fruit crop in subtropical regions,we collected and analyzed sRNA deep-sequencing datasets and degradome libraries Apart from identifying miRNAs and phased siRNA generating loci(PHAS loci),120 hairpin loci,producing abundant sRNAs,were identified by in-house protocols.Our results suggested that 56 miRNA-target pairs,2221-nt-PHAS loci,and 111 hairpin loci are involved in posttranscriptional gene silencing during longan reproductive development.Lineage-specific or species-specific post-transcriptional regulatory modules have been unveiled,including miR482-PHAS and miRN15.miR482-PHAS might be involved in longan flower development beyond their conserved roles in plant defense,and miRN15 is a novel miRNA likely associated with a hairpin locus(HPL-056)to regulate strigolactone receptor gene DWARF14(D14)and the biogenesis of phasiRNAs from D14.These small RNAs are enriched in flower buds,suggesting they are likely involved in post-transcriptional regulatory networks essential for longan flower development via the strigolactone signaling pathway.

Phytochemical constituents and biological activities of longan (Dimocarpus longan Lour.) fruit: a review

Longan(Dimocarpus longan Lour.),as an edible fruit and traditional Chinese medicine,has been consumed for thousands of years.Longan pulp has abundant nutritional phytochemicals such as protein,carbohydrate,vitamin C,polysaccharides,polyphenols,which shows multiple biological activities including antioxidant,immunomodulatory and antitumor effects.Longan pericarp also demonstrates biological activities because of its rich content of polysaccharides and polyphenols.This review summarizes the bioactive compounds and bioactivities of longan pulp and aims to provide comprehensive information for future development of longan as a functional health food.

Genome-wide analysis of the CCCH zinc finger family in longan:Characteristic identification and expression profiles in Dimocarpus longan Lour

CCCH(C3 H) Zinc finger(Znf) transcription factors(TFs), as a novel type of Znf gene, regulate the expression of genes by binding to their mRNAs and play important roles in plant growth and development and abiotic stress resistance.Longan(Dimocarpous longan) is a tropical/subtropical fruit tree of great economic importance in Southeast Asia.However, genomic information on C3 H and their functions in longan are still unknown. In this study, a comprehensive analysis of the longan C3 H(DlC3 H) gene family was carried out. A total of 49 DlC3 H genes in three clades were identified from the longan genome database. Characteristics of the genes were analyzed with respect to gene structure,motif composition, phylogenetic tree and potential functions. The analysis of alternative splicing(AS) events suggested that AS events in DlC3 H genes were related to the transformation from longan non-embryonic to embryonic cultures.Promoter analysis indicated that most of the DlC3 H genes included cis-acting elements associated with hormones and stresses responses. Quantitative real-time PCR(qRT-PCR) analysis indicated that 26 of the 49 DlC3 Hs, which possess methyl jasmonate(MeJA) and abscisic acid(ABA) responsive cis-acting elements, showed differential expression patterns under treatment with ABA, MeJA and their endogenous inhibitors, suggesting that DlC3 Hs might be involved in the ABA and MeJA signaling pathways. The expression profiles of 17 of the 49 DlC3 Hs in non-embryonic callus and three tissues of embryonic cultures showed that only five of the 17 DlC3 Hs had the same expression trends as the FPKM trends in transcriptome data;the expression levels of DlC3 H07/14/16/36/49 in embryogenic callus and DlC3 H04/38 in globular embryos were high, suggesting that they have different functions in embryonic development. Further, we verified that DlC3 H01/03/05/11/19/39 were regulated by sRNAs by a modified 5’ RLM-RACE method. This study provides the first systematic analysis of C3 H genes in longan, and found that C3 H genes may be involved in hormone and stress responses, and somatic embryogenesis. Our preliminary investigation may provide clues to further studies on the characteristics and functions of this family in longan.

Optimization of Extraction Process for Longan(Dimocarpus longan Lour.)Leaves Using Multi-indicator Comprehensive Evaluation Method

[Objectives]This study aimed to optimize the extraction process of longan(Dimocarpus longan Lour.)leaves by multi-indicator comprehensive evaluation method.[Methods]The contents of gallic acid ethyl ester,astragalin,quercetin,luteolin and kaempferol in longan leaves were determined simultaneously by HPLC.Using the multi-indicator comprehensive evaluation method,the methanol concentration,solid to liquid ratio and extraction time for extraction of longan leaves were optimized by orthogonal test.[Results]The optimal extraction process of longan leaves are as follows:methanol concentration of 100%,solid to liquid ratio of 1∶5,and extraction time of 50 min.[Conclusions]The optimized process is simple and feasible,and it can be used to determine the contents of different ingredients in longan leaves.

龙眼拟茎点霉(Phomopsis longanae Chi)的生物学特性研究

龙眼拟茎点霉（Phomopsis longanae Chi）是导致采后龙眼果实腐烂的主要病原菌,研究了温度、湿度、pH值、光照、营养、越冬越夏等条件对龙眼拟茎点霉菌丝生长、产孢和孢子萌发的影响。结果表明：龙眼拟茎点霉生长适温为25℃,最适pH6~7;产生子座的最适温度为22~25℃,最适pH6,还需要一定的光照;以蔗糖、葡萄糖、可溶性淀粉和D-果糖为碳源和以蛋白胨、硫酸铵和硝酸铵为氮源的培养基最有利于龙眼拟茎点霉的生长发育;分生孢子的大量萌发要求高湿度和营养刺激,最适萌发温度25~28℃,最适pH6~7,在分生孢子器中,分生孢子的存活时间长于1年;该菌菌丝的致死温度为59℃（10 min）,分生孢子为50℃（10 min）。

A Preliminary Analysis of the Relationship between Longan Canopy Temperature and Air Temperature during Overwintering Period

[Objective] The study aimed to provide supports for developing chilling and freezing injury monitoring and disaster damage assessment of longan(Dimocarpus Longan Lour.).[Method] Based on field observation data,the relationships between longan canopy temperature and air temperature under different weather types(sunny,cloudy to sunny,cloudy,rainy,radiation chilling injury and advection chilling injury)in 2007-2008 winter were analyzed.[Result] Diurnal variations of longan canopy temperature under sunny and radiation chilling injury weather conditions were most dramatic,followed with those under cloudy to sunny condition,while variations under cloudy,rainy and advection chilling injury conditions were mild.Diurnal variations of orchard air temperature were also closely related to weather types.By using linear and curvilinear regression methods,the relationship models between longan canopy temperature and observation station air temperature were established.The models for cloudy,rainy and advection chilling injury had better effects than those for sunny,cloudy to sunny and radiation chilling injury;the models for night were better than those for daytime and the whole day.[Conclusion] To some extent,applying the relationship models between longan canopy temperature and observation station air temperature could make up the shortcoming of meteorological data which were higher than the real values.

Indicator Analysis of Off-season Longan Flower Reversal

[Objectives] This study was conducted to analyze the internal causes of flower reversal in Longan （ Dimocarpus longan Lour.） trees. [Methods] With flowering trees and flower reversal trees as experimental materials, the variations in sugar and starch in mature leaves, tender leaves, mature branches, twigs and terminal buds after flower forcing were analyzed. [Results] During flowering process, sugar content showed the greatest difference between flowering and flower reversal trees, and the difference was the greatest in mature leaves. Trees with mature leaves having a sugar content above 44.71 mg/g were found to be more prone to flowering, while those with leaf sugar content lower than 27.80 mg/g were susceptible to flower reversal. In addition, longan trees with a higher sugar content in tender leaves were not prone to flower reversal. [Conclusions] In future, whether off-season flower forcing can be performed on longan trees could be judged through the detection of tree leaves, which is of great significance to prevention of flower reversal in off-season longan production.

反季节龙眼不同发育时期果实脱落响应差异与果实呼吸耗氧量的关系

反季节龙眼在果实发育过程中落果现象非常严重。前期的研究表明,果实中碳水化合物水平的下降与果实脱落密切相关。为了进一步了解不同发育时期果实的碳水化合物代谢变化与脱落差异的关系,以反季节储良龙眼为试材,果穗从树上剪下后迅速插入清水中并去除叶片诱发果实脱落,通过测定胁迫处理下3个发育时期果实落果率、呼吸耗氧量、果柄分离力变化,检测不同光强对3个时期果实呼吸的影响,发现不同发育时期龙眼果实对脱落的敏感性不同。饥饿胁迫迅速启动了各发育时期果实的脱落响应,但3个时期果实脱落响应差异较大,幼果期果实对饥饿胁迫的响应较中期和后期延后2 d,果实发育中期和后期脱落响应更剧烈;幼果期果实呼吸耗氧量较低,而果实发育中期和后期呼吸耗氧量较高;随着光强的增加,仅幼果期果实呼吸作用未造成氧气的下降,还出现了氧气的释放。幼果期果柄分离力下降也较果实发育中期和后期缓慢。因此,本研究结果表明,在胁迫条件下果实呼吸作用与果实脱落密切相关,果实呼吸强度越强;在饥饿胁迫条件下果柄分离力下降越快,果实脱落越快。龙眼幼果期可通过果皮进行光合作用部分代偿呼吸对碳水化合物的消耗。幼果期饥饿胁迫下落果慢的主要原因是低的呼吸消耗和具有一定的光合能力,因此,龙眼幼果是一个部分自养的器官。

大果龙眼新品种良圆龙眼的选育

良圆龙眼是以大乌圆为母本、储良为父本杂交选育的大果龙眼新品种。果实大小均匀,单果质量13~18 g;果皮黄褐色,果实外观较好;果肉乳白色,稍透明,果肉表面纵纹明显,表面不流汁,汁液中多,肉离核、韧脆化渣,味甜;可食率64%~69%,可溶性固形物含量(w)19%~21%。树势强,树姿直立,树冠圆形,1年生枝条较粗,优于两亲本。在广州地区成熟期7月底至8月上中旬;丰产性中等,高接后第5年平均株产为22.5 kg,每666.7 m^(2)产量可达724.5 kg;适宜广东省各产区栽培。

龙眼DlSWC5基因克隆、亚细胞定位及表达特性分析

【目的】克隆龙眼ATP依赖的染色质重塑相关基因DlSWC5,并分析其亚细胞定位及表达特性,为研究该基因在龙眼生长发育及早期体胚发生过程中的调控功能提供理论依据。【方法】以龙眼品种红核子体胚发生早期胚性愈伤组织(Embryogenic callus,EC)为试验材料,结合龙眼三代基因组数据,采用RT-PCR克隆DlSWC5基因cDNA序列,对其进行生物信息学分析,基于STRING数据库预测DlSWC5蛋白互作调控网络,并通过激光扫描共聚焦试验验证蛋白亚细胞定位情况。分别利用转录组测序技术和实时荧光定量PCR检测DlSWC5基因在体胚发生早期和不同组织及不同浓度吲哚乙酸(IAA)处理下EC中的表达情况。【结果】成功克隆出DlSWC5基因的cDNA序列,与基因组中DlSWC5基因CDS序列相似性达99.80%,共编码340个氨基酸残基,该蛋白不含信号肽和跨膜结构,共含有44个磷酸化位点,分子式为C_(1622)H_(2599)N_(459)O_(542)S_(8),相对分子质量为37458.71 Da,理论等电点(pI)为5.74。DlSWC5蛋白结构的预测结果显示,其二级结构包含48.53%的α-螺旋、40.29%的无规则卷曲、6.47%的延伸链、4.71%的β-转角,其三级结构与漾濞槭同源蛋白高度一致。蛋白互作预测结果显示,DlSWC5蛋白与PIE1、SWC2、SWC4等10个蛋白互作。亚细胞定位显示DlSWC5蛋白定位于细胞核中。DlSWC5基因的相对表达量在早期体细胞胚胎发生中无明显差异。DlSWC5基因在体胚发生早期及种子、根、茎、叶、花蕾、花、果皮、果肉、幼果等组织中均检测到表达,与对照组(0 mg/L)相比,DlSWC5基因的相对表达量在0.5、1.0、1.5和2.0 mg/L IAA处理24 h后均显著降低(P<0.05)。【结论】成功克隆了DlSWC5基因,其编码蛋白为不稳定的亲水性蛋白,呈酸性,定位于细胞核;DlSWC5基因在龙眼体胚发生早期EC阶段被IAA诱导下调表达。

外源甜菜碱与褪黑素复合处理对龙眼果实贮藏性能的影响

目的研究不同浓度甜菜碱与褪黑素复合处理对采后龙眼果实冷藏的保鲜效果,以期为龙眼贮藏保鲜新技术提供理论参考。方法以‘储良’龙眼为实验材料,分别采用0、5、10、15 mmol/L的甜菜碱与300 mmol/L的褪黑素复配制成保鲜剂处理果实。在温度为4℃、相对湿度为85%条件下贮藏,研究其冷藏期间质量损失率及可溶性固形物(TSS)、可滴定酸(TA)、抗坏血酸(VC)、丙二醛(MDA)、游离脯氨酸含量和过氧化氢酶(CAT)、过氧化物酶(POD)、超氧化物歧化酶(SOD)活性的变化。结果与300 mmol/L褪黑素对照组相比,复合保鲜剂能有效减少龙眼果实水分、TSS、TA、VC和游离脯氨酸含量的损失,使龙眼果肉保持较高的SOD、CAT活性(P<0.05),而POD活性和MDA含量维持在较低水平。结论300mmol/L褪黑素+10 mmol/L甜菜碱处理对龙眼的冷藏保鲜效果最佳。

基于HPLC指纹图谱和多组分含量测定结合化学模式识别研究的龙眼核质量评价

目的 建立龙眼Dimocarpus longan Lour.核HPLC指纹图谱及含量测定方法。方法 建立13批龙眼核指纹图谱,结合指纹图谱相似度评价及化学模式识别研究对龙眼核质量进行分析,并测定其中没食子酸、柯里拉京、鞣花酸的含量。结果 13批龙眼核样品相似度在0.919~0.999,标定共有峰11个,并指认出3种成分;聚类分析(HCA)将13批龙眼核聚为3类,主成分分析(PCA)提取到3个主成分,正交偏最小二乘判别分析(OPLS-DA)筛选出5个差异性成分;定量分析得到13批龙眼核中没食子酸、柯里拉京金、鞣花酸的含量范围依次为0.65~1.8 mg·g^(-1)、3.02~5.46 mg·g^(-1)、3.18~4.49 mg·g^(-1)。结论 建立的HPLC指纹图谱及含量测定方法重复性、稳定性良好,能够为龙眼核质量评价提供参考。

龙眼DlSWEET1基因的克隆、表达及功能分析

【目的】SWEET(sugars will eventually be exported transporters)是一类参与植物生长发育多个过程的糖转运蛋白,分析DlSWEET1基因在龙眼不同组织和处理下的表达,探究其在果实糖积累中的功能。【方法】以龙眼松风本果实为材料,克隆DlSWEET1基因,采用实时荧光定量PCR分析DlSWEET1在龙眼不同组织器官的表达以及在激素、冷、热、干旱胁迫下的表达模式。通过亚细胞定位、糖转运活性分析及草莓瞬时转化研究DlSWEET1基因的功能。【结果】DlSWEET1基因开放阅读框(ORF)全长为750 bp,编码249个氨基酸,包含一个PQ-loop保守结构域和蛋白典型保守结构域MtN3_slv。DlSWEET1在龙眼根、茎、叶、果肉等组织中均有不同程度的表达,在叶中的表达量较高,在果肉中的表达量次之,而在茎和根中表达量较低;不同浓度的蔗糖、葡萄糖和果糖处理龙眼叶片后,DlSWEET1在叶片中的表达量均有显著升高;低温、干旱及MeJA(茉莉酸甲酯)处理可显著提高DlSWEET1的表达。农杆菌侵染本氏烟草发现DlSWEET1蛋白定位在细胞膜和细胞核。糖转运活性分析证明DlSWEET1蛋白可以转运葡萄糖、果糖、蔗糖和甘露糖。草莓中瞬时转化DlSWEET1可以显著提升果实中的可溶性糖含量。【结论】瞬时过表达DlSWEET1导致转基因草莓果实的可溶性糖含量增加,为进一步解析DlSWEET1在龙眼果实糖积累中的作用提供理论依据。

龙眼叶黄酮类有效组分配伍体外降糖作用的研究

基于体外降糖活性优选龙眼(Dimocarpus longan Lour.)叶黄酮有效成分山柰酚、槲皮素、槲皮苷的配伍比例。建立HepG2细胞胰岛素抵抗模型,分别考察不同浓度的胰岛素及不同诱导时间对胰岛素抵抗模型的诱导情况,并以山柰酚、槲皮素、槲皮苷三者用量为考察因素,以对胰岛素抵抗的HepG2细胞葡萄糖消耗率为指标,运用星点设计-效应面法(CCD-RSM)优化三者配伍比例。结果表明,建立HepG2细胞胰岛素抵抗模型的最佳条件为1×10^(-7)mol/L胰岛素诱导24 h;山柰酚、槲皮素、槲皮苷体外降糖最佳配伍比例为山柰酚105.0μmol/L、槲皮素78.9μmol/L、槲皮苷194.0μmol/L,配伍比例优化试验拟合方程为Y=20.94+1.55×A-0.44×B-2.05×C-0.66×AB+1.68×AC-1.53×A^(2)-3.2×B^(2)-2.68×C^(2)。山柰酚、槲皮素、槲皮苷3种单体的联合使用对HepG2细胞的葡萄糖消耗率预测值是21.52%,实验值是(21.05±0.52)%。优选出的最佳配伍比例的龙眼叶黄酮类有效组分,对HepG2细胞的葡萄糖消耗率最高,降糖活性较好,可为龙眼叶治疗糖尿病的有效性提供科学方法与实验依据。

不同疏花方式对龙眼开花坐果及果实品质的影响

通过对龙眼不同疏花方式处理组和对照组的观察和数据分析,探究了疏花方式不同对开花坐果及果实品质的影响。结果显示:完全疏花组的开花数量和果实数量显著减少,坐果率降低,但果实品质较好;部分疏花组保留了适量的花蕾,开花数量相对较多,坐果率相对较高,保持一定的产量和较好的果实品质;延迟疏花组保留了所有花蕾,开花数量最多,但坐果率受到影响,果实品质相对较差。研究结果可为龙眼种植者提供一定的参考和指导,为龙眼品种改良和栽培技术的发展提供理论基础和实践指导。

A New Diol from Dimocarpus longan Seeds

Objective To investigate the chemical constituents of Dimocarpus longan seeds in Sapindaceae.Methods The chemical constituents were isolated from the ethanol extract of D.longan seeds by silica gel column chromatography.Their structures were identified on the basis of physical and chemical properties and spectral analysis.Results One compound was isolated and identified as 2-methyl-1,10-undecanediol,named longandiol(1).Conclusion Compound 1 is a new compound.

酸枣仁提取物、龙眼肉提取物、γ-氨基丁酸和酪蛋白水解物复配制剂改善睡眠功能

本文通过直接睡眠实验、延长戊巴比妥钠睡眠时间实验、戊巴比妥钠阈下剂量催眠实验以及巴比妥钠睡眠潜伏期实验,研究了酸枣仁提取物、龙眼肉提取物、γ-氨基丁酸和酪蛋白水解物复配制剂对小鼠睡眠的改善效果。实验选取48只小鼠作为研究对象,随机分成对照组、高、中、低剂量组,灌胃复配制剂4周后,测定相应指标。结果显示,该复配制剂在高、中、低三个剂量下均可显著延长戊巴比妥钠诱导的小鼠睡眠时间,高剂量组睡眠时间为3793±1100 s,中剂量组睡眠时间为3591±1589 s,低剂量组睡眠时间为3218±582 s,而对照组的睡眠时间仅为1556±686 s。复配制剂的高中低剂量组均可缩短巴比妥钠催眠小鼠的入睡潜伏期,入睡潜伏期分别为171±58 s、165±40 s和184±52 s,对照组的入睡潜伏期为300±155 s。复配制剂所有剂量组均对直接睡眠无明显作用,对小鼠体重均无显著性影响。

龙眼DlAGO4和DlAGO6启动子的克隆及活性分析

【目的】Argonaute(AGO)蛋白是RNA介导的沉默复合物RISC的核心成分,参与植物生长发育、组织形成、细胞增殖凋亡、病毒防御、逆境响应等多种生物过程。探究龙眼DlAGO4和DlAGO6基因启动子区域的顺式作用元件,以及重组表达载体在不同激素处理下的表达模式,可为进一步研究DlAGO4和DlAGO6基因的功能提供参考。【方法】使用常规PCR技术克隆龙眼DlAGO4和DlAGO6基因启动子序列,采用BPDG、PLACE和PlantCARE等生物信息学工具进行DlAGO4和DlAGO6基因启动子序列的生物信息学分析,并构建全长启动子与GUS基因融合表达载体,转化烟草叶片,进行瞬时表达,通过GUS组织化学染色分析启动子的活性。【结果】DlAGO4基因启动子片段长度1514 bp,DlAGO6基因启动子片段长度1784 bp。两个启动子序列均含有TATA-box和CAAT-box核心元件、茉莉酸甲酯、脱落酸和光响应元件;DlAGO4启动子序列还含有水杨酸、赤霉素响应元件和厌氧应答调控元件;DlAGO6启动子序列还含有生长素及昼夜节律调控元件。2个启动子片段均可驱动GUS基因表达,表达强度弱于CaMV35S。MeJA和ABA处理可显著提高转DlAGO6启动子烟草叶片中GUS基因的相对表达水平,SA和MeJA处理可提高转DlAGO4启动子烟草叶片GUS基因的相对表达水平。【结论】成功克隆了龙眼DlAGO4和DlAGO6基因启动子,二者为激素诱导型启动子,具有驱动下游GUS表达的活性,可能参与了植物体胚发育以及对激素的响应。

龙眼蛋白对C57BL/6小鼠及RAW264.7巨噬细胞的炎症因子的影响研究

目的探讨龙眼蛋白对C57BL/6小鼠及RAW264.7巨噬细胞的炎症因子影响及作用机制。方法采用反向色谱-质谱法(reverse-phase liquid chromatography-mass spectrometry,RPLC-MS)鉴定龙眼蛋白的组成。采用100 mg/(kg·d)和200 mg/(kg·d)龙眼蛋白腹腔注射C57BL/6小鼠,酶联免疫吸附法(enzyme linked immunosorbent assay,ELISA)测定小鼠血液炎症因子的表达,苏木精-伊红(hematoxylin-eosin,HE)染色法染色分析肺部炎症病理反应;用0.2、0.4、0.6 mg/mL龙眼蛋白处理小鼠RAW264.7巨噬细胞,噻唑蓝[3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide,MTT]法测定细胞活力,实时荧光定量聚合酶链式反应法(real-time quantitative polymerase chain reaction,Q-PCR)和ELISA检测炎症因子表达,蛋白质免疫印迹法(western blot,WB)分析腺苷酸活化蛋白激酶(AMP-activatedprotein kinase,AMPK)/核因子κB(nuclear factor kappa-B,NF-κB)信号通路相关蛋白表达情况。结果通过RPLC-MS结合数据库检索,共鉴定到肽段覆盖率在30%以上的蛋白质25种。腹腔注射100 mg/(kg·d)龙眼蛋白使小鼠肺部产生炎症病理反应,小鼠血清中的炎症因子[血清淀粉样蛋白A(serum amyloid A,SSA)、超敏C反应蛋白(hypersensitive C-reactive protein,hs-CRP)、降钙素原(procalcitonin,PCT)、白细胞介素-6(interleukin-6,IL-6)]均显著升高。0.2 mg/mL龙眼蛋白处理使RAW264.7细胞IL-6、白细胞介素-8(interleukin-8,IL-8)、肿瘤坏死因子-α(tumor necrosis factorα,TNF-α)的m RNA和蛋白表达均呈剂量依赖式上升,AMPK磷酸化水平表达下调,p65磷酸化水平表达上调。结论龙眼蛋白能够促进小鼠和RAW264.7巨噬细胞的炎症反应,其作用机制可能是龙眼蛋白促进了AMPK/NF-κB信号通路相关炎症因子的表达。

茉莉酸甲酯处理对采后龙眼果皮褐变的影响

本实验以10、50、100μmol/L MeJA处理‘储良’龙眼(Dimocarpus longan Lour.)果实,研究其对(20±1)℃、85%相对湿度贮藏条件下的龙眼果皮褐变的影响。结果表明:与对照组相比,MeJA处理可有效降低‘储良’龙眼采后果皮褐变指数、果皮细胞膜透性和果肉自溶指数,而且MeJA浓度越高,抑制效果越明显。与对照组相比,100μmol/L MeJA处理龙眼果实能够保持较高的果皮总酚和类黄酮含量,降低果皮多酚氧化酶活力,有效提高果皮过氧化物酶和苯丙氨酸解氨酶活力;另一方面,MeJA处理可以有效降低超氧阴离子自由基产生速率以及H2O2含量,有效增强抗氧化酶(超氧化物歧化酶、过氧化氢酶)活力以及1,1-二苯基-2-三硝基苯肼自由基清除能力,提高果皮抗氧化能力。综上,100μmol/L MeJA处理可抑制龙眼果实采后部分酚类物质代谢,增强其抗氧化能力,从而延缓龙眼采后果皮褐变的发生,延长贮藏保鲜期。