基于核磁共振技术的合欢种子吸水特性_杜恬恬.pdf

第 58 卷 第 4 期2 0 2 2 年 4 月林业科学SCIENTIASILVAESINICAEVol.58,No.4Apr.,2 0 2 2doi:10.11707/j.1001-7488.20220403收稿日期:2021-01-27;修回日期:2021-12-30。基金项目:江苏高校优势学科建设(PAPD)。李淑娴为通讯作者。基于核磁共振技术的合欢种子吸水特性杜恬恬1 代松2钱滕3朱铭玮1陈丽1张中会4李淑娴1(1.南京林业大学南方现代林业协同创新中心南京 210037;2.铜仁科学院铜仁 554300;3.安徽林业职业技术学院合肥 230031;4.苏州泰纽测试服务有限公司苏州 215163)摘要:【目的】采用核磁共振技术,从时间、空间角度探究热水处理后合欢种子的初始吸水位点及水分的动态移动过程,揭示其内部水分相态的变化,为合欢种子吸水特性研究提供一种全新的技术手段。【方法】对始温80 热水处理后的合欢种子,用称重法确定种子吸水曲线,用核磁共振成像技术(MRI)观察初始吸水位点及水分在种子体内的移动规律,同时结合横向弛豫时间 T2,探究吸水过程中水分相态及其含量、比例的动态变化。【结果】1)合欢种子吸水曲线呈“S”型变化,吸水前期(04 h)种子吸水率缓慢增加;412 h 进入快速吸水阶段,吸水率增幅较大;吸水 12 h 后进入缓慢吸水期。核磁共振成像结果表明,水分最初从种孔进入种子,然后通过 3条路线移动:沿着种皮两侧的维管束向合点端移动;通过种皮与子叶的缝隙向下(合点端)移动,同时进入子叶的外侧;水分通过胚根进入胚轴,由胚轴进入子叶并向合点端移动,但其移动速度明显慢于第二条。吸水初期(0 6 h),右侧种皮的吸胀面积明显大于左侧,之后随浸种时间延长,左侧吸水速度较快,吸胀面积与右侧无明显差异。2)核磁共振波谱图表明,合欢种子水分质量(X)与核磁共振弛豫图谱峰面积(S)呈显著线性关系:S=21 132X+695.05,R2=0.999 6。3)核磁共振驰豫图谱结果表明,合欢种子内主要存在 3 种状态的水,分别是结合水、胞内水和胞外自由水。4)在 0 h 时,结合水占 45.13%,胞外自由水占 53.51%,几乎没有胞内水。在吸水过程中,结合水含量明显减少,比例持续降低,在 48 h 时仅占 2.08%;胞内水比例呈先迅速增加后逐渐减小的变化趋势,胞外自由水的比例一直呈上升趋势,在 48 h 时二者分别为 29.12%、68.80%。整个吸水过程中 3 种状态水分含量的比例始终处于动态变化中,并且胞外自由水的含量远高于其他状态的水。吸水过程中结合水与胞外自由水的峰顶点呈现左移现象(即流动性在减弱)。【结论】种孔是合欢种子的最初吸水位点,水分进入后通过两侧种皮、种皮与子叶缝隙以及胚轴向合点端移动。吸水过程中,合欢种子中始终存在结合水、胞内水、胞外自由水这 3 种相态的水,且在整个吸胀过程中相互转化,为种子萌发提供前期准备。关键词:合欢;吸水;核磁共振技术;水分相态中图分类号:S718.43文献标识码:A文章编号:1001-7488(2022)04-0022-10Water Absorption Characteristics of Albizzia julibrissin Seeds by Nuclear Magnetic Resonance TechniqueDu Tiantian1Dai Song2Qian Teng3 Zhu Mingwei1Chen Li1Zhang Zhonghui4Li Shuxian1(1.Co-Innovation Center for the Sustainable Forestry in Southern ChinaNanjing 210037;2.Tongren Academy of SciencesTongren 554300;3.Anhui Vocational&Technicial College of ForestryHefei 230031;4.Suzhou Tainew Test Service Co.LtdSuzhou 215163)Abstract:【Objective】Imbibition is the initial and most important stage of seed germination.Nuclear magnetic resonance(NMR)technology was used to explore the initial water absorption site and the spatial and temporal movement of water throughout the seed after hot water treatment from the perspective of time and space,revealing the changes of water phase in seeds.Thisprovides a new method for the study of water absorption in seeds.【Method】The seeds of A.julibrissin were treated with hot water at an initial temperature of 80 .The water absorption was calculated by the increase in weight after soaking divided by the initial weight.MRI technology was used to observe the initial water absorption location and the movement of water in the seeds after water absorption,combined with T2 relaxation detection 第 4 期杜恬恬等:基于核磁共振技术的合欢种子吸水特性technology to explore the dynamic changes in phase and state of the water.【Result】1)The water absorption curve of A.julibrissin seeds exhibited an“S”type behavior,where the water absorption of seeds increased slowly in the early stage(0-4 h);the seeds entered the rapid water absorption stage during 4-12 h,where the water absorption increased greatly;finally the seeds entered the slow water absorption stage at 12 h.During the process of water absorption,the MRI result of the seeds showed that the water initially entered the seeds from the micropyle,then migrated inside the seed through three paths,namely:The water moved along the vascular bundle at the seed coat toward the chalazal;The water moved down towards the chalazal through the gap between the seed coat and cotyledons,entering the lateral side of cotyledons;The water entered the hypocotyl through the radicle,then entered the cotyledons and moved to the chalazal,but its moving speed was noticeably slower than that of the second path.At the initial stage of water absorption(0-6 h),the imbibition area of the right seed coat was significantly larger than that of the left.Later,with the extension of soaking time,the imbibition speed of the left seed coat was faster,and there was no significant difference between the imbibition area of the left seed coat and that of the right seed coat.2)The NMR spectrum showed that the water content(X)of A.julibrissin and the peak area(S)had a linear relationship,and the linear regression equation was:S=21 132X+695.05,R2=0.999 6.3)There were three main states of water in A.julibrissin seeds,namely bound water,cytoplasmic bulk water,and extra-cellular free water.4)At 0 h,bound water accounted for 45.13%of the water in the cell,extracellular free water accounted for 53.51%,and cytoplasmic bulk water was almost absent.During the process of water absorption,the content of bound water decreased significantly,which continued to decrease,accounting for only 2.08%by 48 h;the content of cytoplasmic bulk water increased rapidly at first and then decreased gradually.The content of extra-cellular free water increased continuously.At 48 h,the percentages of cytoplasmic bulk water and extra-cellular free water were 29.12%and 68.80%,respectively.During the whole process of water absorption,the percentages of water phases in three states was always in dynamic change,and the content of extracellular free water was much high