共查询到20条相似文献，搜索用时 157 毫秒
1.
本文通过对有丝分裂实验材料的改进,将人教版教材中洋葱或大蒜的根尖改为葱或大蒜的茎尖进行实验。实验发现,葱的茎尖及大蒜鳞芽形成期前的茎尖均可作为实验材料且分裂相明显。结果表明,葱或大蒜的茎尖比根尖易获取,且制成的装片可观察到更多分裂相。 相似文献
2.
王小利 《实验室研究与探索》2012,31(10)
利用具有优良抗逆性状基因的中国野生葡萄与品质好的栽培品种杂交培育优质、抗逆性强的综合性新品种,是解决现有品种存在抗性差问题的有效途径,而染色体鉴定是葡萄多倍体诱导和杂交育种的基础.分别以葡萄的幼芽、茎尖、幼叶、卷须和根尖为材料,利用去壁低渗-压片法和改良苯酚品红染色法探讨葡萄染色体鉴定最适合的材料和方法.结果显示,幼芽和根尖在有丝分裂中期的细胞数最多,最适合做染色体制片的材料,其次为卷须、茎尖和幼叶组织;综合取材难易、试剂及程序方法复杂的程度,去壁低渗-压片法适合取材比较容易的幼芽组织;改良苯酚品红染色法程序适合根尖细胞.为葡萄染色体鉴定提供了最有效的借鉴方法. 相似文献
3.
植物组织培养中用到的实验材料主要是离体的植物器官、组织或细胞,其中的组织可以是芽、茎尖、根尖或者是花药,根据细胞的全能性,实验材料通过脱分化、再分化得到的根、芽,最后培养成植物体。实验中用到的芽、茎尖、花药在培养前细胞中是有叶绿体,但是在培育成的植物体的根等后 相似文献
4.
欧洲大黄茎尖组织培养与快速繁殖 总被引：1，自引：0，他引：1
就四个欧洲大黄品种的的茎尖组织培养与快速繁殖技术进行了比较研究。结果表明欧洲大黄可用茎尖作为外植体进行离体室内人工快繁。茎尖在MS诱导培养基上培养4周后衍生幼苗。幼苗在MS生根培养基上培养4周可发育出完整的根系。不同品种之间在离体繁殖条件下的衍生能力有较大差异。 相似文献
5.
就四个欧洲大黄品种的的茎尖组织培养与快速繁殖技术进行了比较研究.结果表明欧洲大黄可用茎尖作为外植体进行离体室内人工快繁.茎尖在MS诱导培养基上培养4周后衍生幼苗.幼苗在MS生根培养基上培养4周可发育出完整的根系.不同品种之间在离体繁殖条件下的衍生能力有较大差异. 相似文献
6.
利用组织培养可以得到无病毒植株 ,但必须选取去病毒的无性繁殖材料。White早在 1 943年就发现植物生长点附近的病毒很少甚至无病毒 ,因此 ,茎尖、根尖等可作为组织培养天然的无病毒材料 ,无需复杂的脱病毒处理过程。今天茎尖培养已成为获得无病毒植株的最好途径 ,得到了多种植物如菊花、百合、马铃薯、草莓的无病毒植株 ,取得了可观的经济效益。那么根尖无病毒的原因是什么呢 ?目前认为可能的原因有以下几种 :首先 ,许多科学家研究认为 ,造成这种现象的原因与病毒质粒在植物体内的运输和分布的特点有关。病毒在植物体的运输方式概括有两种… 相似文献
7.
观察植物细胞有丝分裂的实验,是高中生物第二章细胞增殖中一个很重要的实验,同时也是本教材中的重难实验。原理是利用茎尖或根尖分生区的细胞正处于分裂的特点,观察分裂间期和分裂期细胞中染色体的形态和数目。目的是进一步理解有丝分裂过程中 相似文献
8.
文章探讨了如何建立马铃薯茎尖分生组织试管苗的再生体系, 包括外植体的获得、分生组织的切取和培养、茎尖分生组织诱导成苗以及快速繁殖等研究。实验共切取和培养110 多个马铃薯茎尖。实验结果表明, (1) 切取的茎尖当直径在013 - 016mm 之间, 并带有2 - 4 个叶原基时成活率较高。(2) 培养马铃薯茎尖分生组织的适宜培养基为MS + 015mg/L IAA + 011mg/L GA + 0104mg/L KT , 茎尖易成活, 也易分化出苗。(3) 茎尖培养在温度为24 - 26 ℃, 光照2000 - 2500 lx , 每天光照12 - 15h 的培养条件下, 将生长得更好。 相似文献
9.
目的:评价与比较iRoot SP配合单尖充填技术与AH plus配合连续波热牙胶充填技术、超声辅助iRoot SP糊剂导入根管加单尖充填技术对根尖封闭效果的影响。方法:收集下颌前磨牙30颗,行根管预备后随机分为3个实验组,分别为iRoot SP加单尖充填技术组、A H plus加连续波充填技术组、iRoot SP配合超声辅助导入根管加单尖充填技术组。选择细菌渗透法——粪肠球菌来评估iRoot SP单尖法根管充填、超声辅助iRoot SP单尖法根管充填以及AH Plus配合热牙胶充填后的根尖封闭性能。结果:三组根尖微渗漏组间比较无统计学差异,但超声辅助iRoot SP单尖法充填组微渗漏时间要晚于其他两组。结论:iRoot SP根管封闭剂加单尖充填技术的根尖封闭效果与AH plus根管封闭剂加连续波热牙胶充填技术的根尖封闭效果相似;超声辅助根充糊剂导入根管有助于提高根管充填质量。 相似文献
10.
问题1：植物组织培养是无性生殖吗？
在高中生物教材中，常把植物组织培养看成是“一项无性繁殖的新技术”，笔者认为这种说法不妥。植物组织培养的生殖类型，应根据植物组织培养所用的培养材料而定，如果所用培养材料是体细胞，如根尖、茎尖等，则属于无性生殖，若是花药离体培养则应属于有性生殖。 相似文献
11.
Disparity in the root morphology of six rice (Oryza sativa L.) genotypes varying in potassium (K) efficiency was studied with three K levels: 5 mg/L (low),10 mg/L (moderate) and 40 mg/L (adequate) in hydroponic culture.Morphological parameters included root length,surface area,volume and count of lateral roots,as well as fine (diameter<0.2 mm) and thick (diameter>0.2 mm) roots.The results indicate that the root growth of all genotypes was reduced under low K,but moderate K deficiency increased the root length of the efficient genotypes.At deficient and moderate K levels,all the efficient rice genotypes developed more fine roots (diameter<0.2 mm) than the inefficient ones.Both fine root count and root surface area were found to be the best parameters to portray K stress in rice.In accordance with the root morphology,higher K concentrations were noted in shoots of the efficient genotypes when grown at moderate and deficient K levels,indicating that root morphology parameters are involved in root uptake for K and in the translocation of K up to shoots.K deficiency affected not only the root morphology,but also the root ultra-structure.The roots of high-efficient genotypes had stronger tolerance to K deficient stress for root membrane damage,and could maintain the developed root architecture to adapt to the low K growth medium. 相似文献
12.
史建红 《吕梁高等专科学校学报》1999,15(4):22-26
本文提出了约束线性模型下回归系统的条件根方估计和广义条件根方估计,证明了在一定的条件下,两者在均方误差意义都能很好地改进回归系数的约束最小二乘估计,并讨论了它们的可容许性及广义条件根方估计中未知参数的选取方法。 相似文献
13.
伯乐树种子萌发与根组织分化规律的研究 总被引：1，自引：0，他引：1
伯乐树（Bretschneidera sinensis Hemsl.）为我国特有,分布稀少,是国家重点保护的二级濒危树种.本文阐述了伯乐树种子萌发的基本参数及根的组织分化过程,包括根尖和初生结构的形成.通过根尖的连续纵切片观察到伯乐树根尖的根冠、分生区、伸长区及成熟区四个部分的细胞形态结构,通过根的横切片,观察根的初生结构的形成过程,初生结构由外至内包括表皮、皮层和维管柱三部分. 相似文献
14.
Effect of seedling age and water depth on morphological and physiological aspects of transplanted rice under high temperature 总被引：2，自引：0，他引：2
Khakwani AA Shiraishi M Zubair M Baloch MS Naveed K Awan I 《Journal of Zhejiang University. Science. B》2005,6(5):389-395
INTRODUCTION Rice (Oryza sativa L.) is one of the most im-portant crops in Pakistan. It is the third largest crop interms of area and production after wheat and cotton.Although rice in Pakistan is consuming large acreage,Pakistan is still far behind other rice producingcountries. The average yield is very low (2 t/ha) ascompared to Egypt (8.4 t/ha) and USA (6.6 t/ha).There are many reasons for this low yield. The mostimportant are high temperature (40?50 °C), low hu-midity at … 相似文献
15.
Jia Y Tang SR Ju XH Shu LN Tu SX Feng RW Giusti L 《Journal of Zhejiang University. Science. B》2011,12(4):313-325
This study was conducted to investigate the combined effects of elevated CO2 levels and cadmium (Cd) on the root morphological traits and Cd accumulation in Lolium multiflorum Lam. and Lolium perenne L. exposed to two CO2 levels (360 and 1 000 μl/L) and three Cd levels (0, 4, and 16 mg/L) under hydroponic conditions. The results show that elevated
levels of CO2 increased shoot biomass more, compared to root biomass, but decreased Cd concentrations in all plant tissues. Cd exposure
caused toxicity to both Lolium species, as shown by the restrictions of the root morphological parameters including root length, surface area, volume, and
tip numbers. These parameters were significantly higher under elevated levels of CO2 than under ambient CO2, especially for the number of fine roots. The increases in magnitudes of those parameters triggered by elevated levels of
CO2 under Cd stress were more than those under non-Cd stress, suggesting an ameliorated Cd stress under elevated levels of CO2. The total Cd uptake per pot, calculated on the basis of biomass, was significantly greater under elevated levels of CO2 than under ambient CO2. Ameliorated Cd toxicity, decreased Cd concentration, and altered root morphological traits in both Lolium species under elevated levels of CO2 may have implications in food safety and phytoremediation. 相似文献
16.
以机械传动系统中的斜齿轮啮合为研究对象,在考虑时变刚度、齿侧间隙和啮合误差的情况下,建立了十自由度斜齿轮非线性振动数学模型。以斜齿轮结构参数作为灵敏度分析参数,采用数值分析方法分别研究了斜齿轮系统振动加速度均方根值对齿轮质量、支撑刚度和支撑阻尼的灵敏度。结果表明:主、被动轮横向（y向）振动对各参数敏感度较低,横向振动（x向）与被动轮扭转振动对质量参数、刚度参数、阻尼参数较为敏感,被动轮扭转振动受到阻尼的影响很大,灵敏度在扭转振动固有频率处变化较大。 相似文献
17.
Combustion kinetic parameters (i.e., activation energy and frequency factor) of coal have been proven to relate closely to
coal properties; however, the quantitative relationship between them still requires further study. This paper adopts a support
vector regression machine (SVR) to generate the models of the non-linear relationship between combustion kinetic parameters
and coal quality. Kinetic analyses on the thermo-gravimetry (TG) data of 80 coal samples were performed to prepare training
data and testing data for the SVR. The models developed were used in the estimation of the combustion kinetic parameters of
ten testing samples. The predicted results showed that the root mean square errors (RMSEs) were 2.571 for the activation energy
and 0.565 for the frequency factor in logarithmic form, respectively. TG curves defined by predicted kinetic parameters were
fitted to the experimental data with a high degree of precision. 相似文献
18.
A new approach to the calculation of the points at which the root locus crosses the imaginary axis is proposed and the corresponding parameters are given. Further, this method to analyze polynomial convexity is used. Examples are given for illustration. It is shown that this approach is simple and useful to determine the Hurwitz stable polynomial. 相似文献
19.
Esther Ulitzsch Jana Holtmann Martin Schultze Michael Eid 《Structural equation modeling》2017,24(1):80-103
This simulation study assesses the statistical performance of two mathematically equivalent parameterizations for multitrait–multimethod data with interchangeable raters—a multilevel confirmatory factor analysis (CFA) and a classical CFA parameterization. The sample sizes of targets and raters, the factorial structure of the trait factors, and rater missingness are varied. The classical CFA approach yields a high proportion of improper solutions under conditions with small sample sizes and indicator-specific trait factors. In general, trait factor related parameters are more sensitive to bias than other types of parameters. For multilevel CFAs, there is a drastic bias in fit statistics under conditions with unidimensional trait factors on the between level, where root mean square error of approximation (RMSEA) and χ2 distributions reveal a downward bias, whereas the between standardized root mean square residual is biased upwards. In contrast, RMSEA and χ2 for classical CFA models are severely upwardly biased in conditions with a high number of raters and a small number of targets. 相似文献
20.
动力电池的荷电状态(State of Charge,SOC)是预估电动汽车剩余有效行驶里程的重要参数之一。为提高锂电池SOC 的估算精度,考虑了温度对锂电池特性的影响。通过实验得到温度对电池容量的关系曲线,以及得到OCV-SOC-T 的函数映射关系,基于二阶RC 等效电路模型,利用带遗忘因子递推最小二乘法(Forgetting Factor Recursive Least Square, FFRLS)对模型进行实时在线参数辨识。在不同温度和工况条件下,采用扩展卡尔曼滤波(Extended Kalman filter,EKF)和无迹卡尔曼滤波( Un-scented Kalman filter, UKF)算法对锂电池的SOC 进行估算并对比验证,结果表明,EKF 在动态压力测试工况(DST)和美国联邦城市运行工况(FUDS) 的均方根误差分别在4.93%和4.69%以内,UKF 在DST 和FUDS 工况下的均方根误差分别在1.47%和1.49%以内。研究结果表明,FFRLS联合EKF和UKF都可以实时估算SOC,且在不同温度和不同工况条件下,UKF算法相较于EKF算法,抗干扰能力更强,估算精度更高,收敛性更好。 相似文献