【作者】 宋平；

【导师】 杨涛；

【作者基本信息】 沈阳农业大学 ， 农业电气化及自动化， 2016， 博士

【摘要】 为研究水稻浸种过程中种子的水分相态、分布特征及其流动规律,应用低场核磁共振原位无损检测技术,采用连续浸种、间歇浸种、药剂浸种及温汤浸种等常见处理方法,对不同品种的水稻种子的浸种过程开展了研究。根据横向弛豫时间乃呈现的多组份特征,区分种子内部的水分相态；通过T2弛豫谱信号幅值的差异,分析水稻种子水变化和流动规律；构建横向弛豫时间与水分相态、水分分层及弛豫谱信号幅值与水分含量的关系模型,实现对水稻浸种过程中种子吸水的定量化研究。利用低场核磁共振成像技术,间歇获取质子密度加权像,研究浸种过程对水稻种子水分分布及流动过程的影响,实现水稻种子浸种过程内部水分传递的动态可视化研究。本研究提出了一种无损的水分检测方法,能够更加直接准确地揭示水稻种子在浸种过程中的水分变化规律,更加直观地揭示了水稻浸种过程种子内部的水分传递过程,为探求水稻种子的最佳浸泡条件以及浸种过程中的水分传递理论模型构建提供数据支持和理论依据。本论文的主要研究内容、试验过程、试验结果及结论总结如下：(1)为研究水稻浸种过程中种子的水分相态及其分布特征,利用低场核磁共振快速、无损、准确的检测技术,通过硬脉冲回波序列(carr-purcell-meiboom-gill sequence,CPMG)测量水稻种子横向弛豫时间T2,根据横向弛豫时间T2的差异区分种子内部的水分相态及其变化规律。试验结果表明：通过乃反演谱横向弛豫时间T2长短的差异,发现水稻浸种过程中种子内部水分存在结合水、自由水2独水分状态,同时可区分出内层水、中层水、外层水3种水分分层；二者均能通过回归方程合理地估测水稻在浸种过程中种子的吸水率情况；通过T2反演谱信号幅值大小的差异,发现水稻浸种过程中的种子总体水分含量不断上升,但由于判定依据及划分方式的不同,二者在水分的流动方式上略显差异。低场核磁共振技术直观地揭示了水稻浸种过程中种子内部的水分变化,试验证明这是一种具有很高效率的水分检测方式。(2)为研究水稻种子在浸泡过程中的水分变化情况,应用核磁共振无损、非侵入的技术优势,根据弛豫时间呈现的多组份特征,通过弛豫谱分析水稻种子不同相态水分的变化和流动过程,确定弛豫谱峰值总面积与水稻种子吸水率的回归方程,研究了水稻浸种过程中吸水量的变化情况。利用低场核磁共振技术,监测沈农9816号、七山占及秀子糯3个品种水稻种子48h浸种过程。每6h时间间隔利用硬脉冲自旋回波CPMG序列获取样品的横向弛豫时间T2反演谱,从而分析浸种过程对水稻种子内部水分分布的影响。试验结果表明：通过弛豫谱峰值总面积可以合理估测水稻种子的吸水率；水稻种子在6h浸种过程中,随着浸泡时间的增加结合水及总水含量变化趋势为不断上升,自由水则呈现不规则的反复变化态势。根据T2反演谱信号幅值计算得到的水稻种子吸水率,发现3个品种在相同浸种时间的各个监测点均反映出秀子糯吸水率最高,沈农9816号吸水率最低,试验结果验证了支链淀粉的吸水性优于直链淀粉。(3)应用低场核磁共振原位无损检测技术,采用间歇浸种、连续浸种、药剂浸种及温汤浸种等处理方法,对水稻种子在浸种过程中的吸水量变化开展了研究。利用横向弛豫时间乃反演谱分析了水稻种子在浸种过程中的水分状态变化及吸水特性。试验结果表明：浸种过程改变了水稻种子内部的水分分布情况,水稻种子吸水量对各种浸种方法均高度敏感,对初始含水量不敏感。采用浸种2h,晾干1h,浸种2h的间歇浸种方式,40%福尔马林50倍液药剂及提高浸种温度均可增加水稻种子浸种过程的吸水量；采用浸种3h,晾干1h,浸种1h的间歇浸种方法式及饱和澄清石灰水、强氯精300倍液均将降低水稻种子浸种过程的吸水量。试验为水稻种子浸种过程中吸水量的测定提供了一种有效的方法,为寻求最佳浸种条件提供了数据支持和理论依据。(4)为研究水稻种子浸种过程中内部水分流动情况,可视化内部水分传递过程,利用低场核磁共振及其成像技术,监测沈农9816号、七山占及秀子糯3个品种水稻种子48h浸种过程。每6h时间间隔利用自旋回波(spin echo,SE)脉冲序列获取样品的质子密度加权像,从而分析浸种过程对水稻种子内部水分分布的影响。试验结果表明：核磁共振是一种有效的水分检测技术,利用水稻种子的质子密度加权像,能够直观检测到种子内部水分分布情况,动态的监测到种子内部水分流动过程,分析发现水分最初是从胚进入种子内部,继而通过种皮的渗透,最后到达胚乳部分。研究结果可以为水稻种子浸种过程中水分传递的理论模型构建提供数据支持。更多还原

【Abstract】 To study the water phase state, distribution characteristics, and flow rules of rice seed during the soaking process, the technology of low field nuclear magnetic resonance in-situ nondestructive testing and the method of continuous soaking, intermittent soaking, medical soaking and hot water treatment were used to research the soaking process of different varieties rice seeds.The water phase inside of the seed was distinguished by the characteristics of multiple components of the transverse relaxation time T2;The moisture change and flow pattern of rice seed were analyzed by the difference of the amplitude of T2 relaxation spectrum;The quantitative research on rice seed soaking was studied by the relational model of transverse relaxation time, water phase, water stratification and relaxation spectrum signal amplitude with the moisture content. This study presents a nondestructive method of moisture detection, the change and transfer of rice seed moisture can be more directly and accurately revealed the in the soaking process, it provides data support and theoretical basis for the best soaking conditions of rice seeds and the model construction of water transfer in the process of seed soaking.The research contents, results and conclusions of this paper are summarized as follows:(1) To study the water phase and distribution characteristics of rice seed in soaking process, the detection technology of low field nuclear magnetic resonance was used which was fast, nondestructive and accurate. The transverse relaxation time T2 of rice seed was measured through the Carr-Purcell-Meiboom-Gill sequence (CPMG), the inner water phase and its change rules were distinguished according to the difference transverse relaxation time T2.Test results show that:it found that the internal moisture of rice seeds in soaking process exists two states, bound water and free water, and presents three water stratification, inner, middle and outer water by different length T2 spectrum inversion of transverse relaxation time T2;Both water state and stratification can estimate water absorption rate through the regression equation; it also found that the total water content of rice seed continues to rise in the process of soaking by the difference of T2 inversion spectrum signal amplitude, but because of the different ways of judgment and classification, there was a slightly different in the way of water flow. Low field NMR intuitively reveals the changes of water inside the rice during seed soaking process, and also provides an efficient seed moisture detection method.(2)The technology of nuclear magnetic resonance which has the advantage of non-destructive, non-invasive was used to study the change of rice seed moisture during soaking. The change and flow process of different moisture state was analyzed by the multi-component characteristics of relaxation time and relaxation spectrum. The change of water content in seed soaking process was studied by the regression equation of total peak area and water absorption rate. Shennong No.9816、Qishanzhan and Xiuzinuo were soaked 48 hours monitored by using low field nuclear magnetic resonance. Transverse relaxation time T2 inversion spectrum was collected by CPMG sequence each 6h, so as to analyze the effects of soaking process on moisture distribution of internal rice seed. The results show that the water absorption rate of rice seeds can be reasonably estimated by the peak area of the relaxation spectrum; In the 6h seed soaking process, the content of bound water and total water were increasing with the immersion time but free water showed irregular changes.It found that the highest water absorption rate was Xuizinuo and the lowest is Shennong 9816 according to the T2 spectrum inversion signal amplitude, during the same soaking time. The test results show that the water absorption of amylopectin is better than amylose.(3) The changes of water absorption during soaking process was studied by using the technology of low field nuclear magnetic resonance in-situ nondestructive testing and the method of continuous soaking, intermittent soaking, medical soaking and hot water treatment.The changes of water state and absorption characteristics were analyzed by the transverse relaxation time T2 inversion in the soaking process. The test results showed that the internal moisture distribution of rice seeds was changed by soaking process, the water absorption of rice seed was highly sensitive to various water soaking method, but not to the initial moisture. By the intermittent soaking methods of soaking 2h, dry 1h, soaking 2h,40% formalin and 50 times medicament liquid and improving the soaking temperature could increase the water absorption of rice seed in soaking process; By the intermittent soaking methods of soaking 3h, dry 1h, soaking 1h, saturated lime water and 300 times strong chlorine liquid could reduce the water absorption; With the increasing temperature of seed soaking, the water absorption was significantly enhanced. The test provides an effective method for the determination of water content in rice seed soaking process, also provides data support and theoretical basis for seeking the best soaking condition.(4) To study the internal moisture flow of rice seed in soaking process and visualize the internal moisture transfer process, the low field NMR and MRI techniques were used to monitor the soaking process of Shennong No.9816, Qishanzhan and Xiuzinuo in 48h. Spin echo, (SE) pulse sequence was used to obtain the proton density weighted image each 6h, so as to analyze the effects of soaking process on rice seed internal moisture distribution. The test results show that NMR is an effective moisture detection technology, the internal moisture distribution and dynamic flow of seeds can be directly detected by the proton density weighted image. It found that water entered the seed originally from the embryo, and finally reached the endosperm by the permeability of seed coat. The research results can provide data support for the theoretical model construction of water transmission of rice seed during the process of soaking.更多还原