植物器官脱落的机制及其研究进展

对植物器官脱落的机制及研究进展情况进行了综述,其中包括脱落的几种研究方法,脱落时离区的解剖学和细胞学特征,离层细胞的生理生化特征。重点对激素在脱落过程中的调节作用进行了综述。     

影响加拿大一枝黄花种子非随机脱落的因素

为揭示加拿大一枝黄花(Solidago canadensis)种群扩散机制, 明确种子的脱落及风传扩散在其种群蔓延中的作用, 在人工环境下测定了不同湍流强度、风速和湿度处理下种子脱落的差异, 并对脱落种子与未脱落种子进行形态学特征对比。结果表明: 加拿大一枝黄花的种子脱落受湍流、风速和湿度等因素的共同影响。水平气流下种子的脱落阈值为5.1 m·s^-1, 并随着风速增加, 种子的脱落率增加。与模拟水平气流相比, 模拟垂直气流下种子的脱落阈值显著偏小。相对于层流状态, 湍流的存在显著提高了种子的脱落率, 平均增幅超过300%; 但单纯提高湍流强度对种子脱落率的影响不显著。增加湿度则显著降低种子的脱落率。种子形态学特征对比结果表明, 脱落种子的冠毛数量和冠毛夹角显著高于未脱落种子。该研究结果为研究加拿大一枝黄花种子脱落规律和风传扩散机制提供了科学依据, 也为其他入侵性杂草种子的扩散机制及入侵过程提供了 借鉴。     

Factors influencing the nonrandom abscission of Solidago canadensis seeds

 为揭示加拿大一枝黄花(Solidago canadensis)种群扩散机制, 明确种子的脱落及风传扩散在其种群蔓延中的作用, 在人工环境下测定了不同湍流强度、风速和湿度处理下种子脱落的差异, 并对脱落种子与未脱落种子进行形态学特征对比。结果表明: 加拿大一枝黄花的种子脱落受湍流、风速和湿度等因素的共同影响。水平气流下种子的脱落阈值为5.1 m·s^–1, 并随着风速增加, 种子的脱落率增加。与模拟水平气流相比, 模拟垂直气流下种子的脱落阈值显著偏小。相对于层流状态, 湍流的存在显著提高了种子的脱落率, 平均增幅超过300%; 但单纯提高湍流强度对种子脱落率的影响不显著。增加湿度则显著降低种子的脱落率。种子形态学特征对比结果表明, 脱落种子的冠毛数量和冠毛夹角显著高于未脱落种子。该研究结果为研究加拿大一枝黄花种子脱落规律和风传扩散机制提供了科学依据, 也为其他入侵性杂草种子的扩散机制及入侵过程提供了借鉴。     

脱落调节物质对植物器官脱落的调控

器官脱落是植物生命过程中重要的生理现象.植物体内的许多激素和非激素类物质(扩展蛋白、H_2O_2、细胞壁水解酶等)都参与脱落过程的调控,而且是相互协同配合,共同发挥作用.本文综述了生长素、乙烯、脱落酸、赤霉素和茉莉酸等植物激素,以及非激素类物质扩展蛋白、H_2O_2和两种主要的细胞壁水解酶(纤维素酶和多聚半乳糖醛酸酶)在植物器官脱落过程中的调控作用,并对它们在植物器官脱落调控中的相互作用进行分析,以期为相关研究提供信息.     

藏药独一味的微性状与显微鉴别研究

采用体视显微镜对藏药独一味的根、茎、叶和果实微性状进行观察，利用生物显微镜观察切片组织构造及粉末显微鉴别特征，扫描电镜进一步观察叶片表面结构特征。藏药独一味药材的微性状特征包括根、茎、叶、果实，而茎粗短，果实细小且易脱落，地上部分鉴定特征主要为叶片和果序，叶片表皮细胞中可见气孔、非腺毛和腺鳞等。地上部分粉末鉴定特征包括非腺毛、叶肉细胞、气孔和纤维等，根的鉴别特征包括针晶和导管等。本研究通过对独一味药材不同部位微性状和显微进行系统研究，归纳了独一味药材性状和显微的鉴别要点，可以为独一味药材鉴别提供参考依据。     

人类子宫颈脱落细胞的数学处理及其应用探讨

本文对十二例宫颈脱落细胞的形态和特征进行了数学分类判别,以便早期发现宫颈癌的可疑病例.此外,还探讨了三种病例分类方法的应用前景.     

散发性大肠癌组织及粪便脱落细胞p53蛋白的检测

为了解大肠癌组织及粪便脱落细胞中 p5 3蛋白表达对大肠癌诊断的临床意义 ,采用 S- P法对 38例大肠癌患者的癌组织及其中的 30例患者的粪便脱落细胞 p5 3蛋白进行检测。大肠癌组织中 p5 3蛋白阳性表达率为 39.47% (15 / 38) ,p5 3蛋白阳性与癌组织的分化程度及是否存在淋巴结转移均无相关性 (P>0 .0 5 )。粪便脱落细胞 p5 3蛋白阳性表达率为 36 .6 7%(11/ 30 ) ,脱落细胞与相应患者的癌组织中的 p5 3表达一致率为 83.33% (2 5 / 30 )。表明粪便中脱落细胞 p5 3蛋白的表达忠实反映了相应癌组织的 p5 3突变情况 ,对其检测有望成为大肠癌诊断及筛查的无创分子途径。同时表明粪便中脱落细胞核保持了肿瘤抗原决定簇的主要结构及生物特征 ,进行免疫细胞化学检测是可行的 ,为进行脱落细胞核其它肿瘤标志物或其它生物研究奠定了可行性的基础     

金沙江干热河谷滇榄仁种子扩散与种子库特征研究

采用随机取样和跟踪调查的方法对滇榄仁(Terminalia franchetii)种子扩散规律、空间分布特征以及种子库动态进行了系统研究。结果表明,滇榄仁种子扩散受到较强的风力作用影响,具有明显的方向性,扩散距离是其树高的1.6倍以上。不同群落类型中,滇榄仁的土壤种子库存在较大差异,但不同时间段的变化趋势基本一致,即在雨季(6月、8月和10月)数量相对较少,12月到翌年4月,数量逐渐增加。滇榄仁植冠种子库从当年10月开始缓慢脱落,到翌年3月达到脱落高峰(15%以上种子此时脱落),然后再次进入缓慢脱落期,翌年6、7月的种子脱落速率最低,但直到翌年10月仍有部分种子(约15%左右)存在于植株冠层。总体来说,不同类型群落中,滇榄仁幼苗更新不良的原因不应是缺乏种源,可能与种子质量以及群落环境等影响群落天然更新的其它因子存在较大关联。同时,滇榄仁土壤种子库数量与植冠种子库的脱落过程存在紧密联系,而植冠种子脱落可能与该区域气候因子存在着较大依存关系,其中,与风力可能存在着正相关,与降雨量和空气相对湿度存在着负相关,这可能是滇榄仁长期以来对干热河谷环境的一种适应特征。     

基于免疫磁珠富集粪便脱落细胞的大肠癌筛选法

大肠癌是目前发病率、致死率均较高的恶性肿瘤,严重危害人民健康生活.现有的临床检测技术均存在一定的局限性,因而限制了其临床应用的范围.与常规临床大肠癌检测相比,粪便脱落细胞检测法具有高特异性、高灵敏性且容易被受试者接受等显著优点.作为最新型的脱落细胞检测法一免疫磁珠富集粪便脱落细胞检测法除具有一般脱落细胞检测法的优点外,还具有细胞回收效率高、肿瘤细胞特异性高等优点.本文阐述了脱落细胞检测大肠癌的原理和基本方法,着重介绍了免疫磁珠富集脱落细胞的原理和操作过程以及针对脱落细胞进行大肠癌检测的多种方法,并对全自动、快速、高通量的自动化脱落细胞检测仪器应用于脱落细胞检测进行了展望.     

子宫颈癌细胞学新型生物标志、诊断标志物的筛选和开发现状

子宫颈癌至今仍是全球范围内一个重要的公共卫生问题，是妇女疾病死亡的主要原因之一。因此，子宫颈癌细胞学的筛查、早期诊断和治疗越来越受到重视，虽然新的技术不断推出使子宫颈癌的早期筛查及诊治水平有了很大提高，但仍缺乏新型的特异性生物学标志物。本文从新的子宫颈癌相关蛋白生物标志物和诊断靶标的发现，治疗子宫颈癌的药物作用、治疗靶标和作用机制的评估，子宫颈癌相关微小核糖核酸作为诊断和治疗靶标的筛选等方面对子宫颈脱落细胞筛查方法的开发和研究进展进行综述，为子宫颈癌的早期筛查和诊断寻找新的生物学标志物。     

Cytokinetic abscission in animal cells

Cytokinesis leads to the separation of dividing cells, which in animal cells involves the contraction of an actin–myosin ring and subsequent fission during abscission. Abscission requires a series of dynamic events, including midbody-targeted vesicle secretion, specialization of plasma membrane domains, disassembly of midbody-associated microtubule bundles and plasma membrane fission. A large number of molecular factors required for abscission have been identified through localization, loss-of-function and proteomics studies, but their coordinate function in abscission is still poorly understood. Here, we review the structural elements and molecular factors known to contribute to abscission, and discuss their potential role in the context of proposed models for the abscission mechanism.     

Spatial and temporal aspects of cell separation in the foliar abscission zones ofImpatiens sultani Hook

Summary The abscission of leaves fromImpatiens sultani Hook. occurs as the direct result of the weakening of a narrow band of cells running transversely across the base of the petiole. This loss of strength of the abscission zone is due to the breakdown of the central cell wall in two or three layers of cells. The process of wall degeneration is first visible 13 hours after the induction of abscission in a small group of cells found just below the concave groove on the adaxial side of the petiole. As the abscission zone gets progressively weaker the area of cells showing wall breakdown expands, spreading through the parenchyma to the lower side of the stele. The walls of the collenchyma and epidermis along the sides and base of the petiole and the central vascular tissues are the last to break down. Experiments in which the abscission zone was dissected into small pieces were undertaken to investigate whether cell wall hydrolysis was a contagious phenomenon, spreading from cell to cell by direct contact. The results of these investigations indicated that there was little requirement for cell to cell contact in either the temporal or spatial integration of cell wall breakdown.     

A novel mechanism of abscission in fronds of Lemna minor L. and the effect of silver ions

Lemna minor L. (duckweed) forms colonies through vegetative propagation because mother fronds remain connected for some time with their daughter fronds by stipes. The colony size is controlled by abscission of stipes at a specific preformed abscission zone. Application of silver ions (Ag(+) ) enhances the rate of frond abscission, thus resulting in smaller colonies. The mechanism behind this process has not yet been identified. Silver caused an abscission response that saturated after 7 h of treatment. The half-maximal effective concentration was 0.72 μm Ag(+) for the standard clone, L. minor St. Other clones of the same species show sensitivities that differ by one order of magnitude. Transmission electron microscopy revealed: (i) large numbers of vesicles close to the plasmalemma in cells adjacent to the abscission zone, which proves a vesicular type secretory activity; and (ii) a moderately electron-dense secretion accumulated in the enlarging intercellular spaces, and seemed to flow from the adjacent cells towards the abscission zone. We assume that increasing pressure causes this material to push apart the cells, thereby causing the break in the abscission zone of the stipe. This is a novel mechanism of abscission that has not previously been described. The same mechanism occurs in stipes of both control and Ag(+) -treated samples. Silver ions only accelerate the process leading to abscission of stipes, without affecting the mechanism involved.     

The influence of Salix leaf abscission on leaf-miner survival and life history

Abstract. 1. Early abscission of mined leaves was an important mortality factor of a Phyllonorycter species (Lepidoptera: Gracillariidae) on Salix lasiolepis Benth. (Salicaceae). A larger percentage of mined leaves abscised early (34.4% in 1990; 24.5% in 1991), and Phyllonorycter survival was greatly reduced in these abscised leaves.
2. Leaf-mining by Phyllonorycter was associated with increased early leaf abscission. An egg removal experiment demonstrated that leaf mining induced this increase in leaf abscission.
3. The induction of early leaf abscission was dependent upon the timing of herbivory and simulated herbivory (mechanical damage). Early mechanical damage induced leaf abscission, late mechanical damage did not. Mines which expanded early were more likely to induce leaf abscission than mines which expanded more slowly.     

Optimal and Spatial Analysis of Hormones,Degrading Enzymes and Isozyme Profiles in Tomato Pedicel Explants During Ethylene-Induced Abscission

Activities of degrading enzymes, hormones concentration and zymogram patterns were investigated during control and ethylene-induced abscission of tomato pedicel explants. Exogenous ethylene accelerated abscission of pedicel explants. It was showed that IAA concentration in abscission zone tended to decline at first and then was reduced before separation in control and ethylene-treatment. Moreover, IAA (indole acetic acid) and ABA (abscise acid) concentrations were elevated in each segment when exposing to ethylene, but GA_{1 + 3} (gibberellin1 + gibberellin3) concentration was decreased in abscission zone and the proximal side. Activities of cellulase, polygalacturonase and pectinesterase in the explants were induced in the separating process and strengthened by ethylene. However, comparing with the proximal side, cellulase and polygalacturonase activities in abscission zone and distal side were higher. Electrophoresis of isozymes revealed that at least three peroxidase and three superoxidase isozymes appeared in the explants, respectively. One peroxidase isozyme exhibited differentially among the three positions in control and ethylene-treatment. One esterase isozyme weakened or disappeared in the following hours, but three novel esterase isozymes were detectable from beginning of the process. The data presented support the hypothesis that the distal side, together with abscission zone of explants plays a more important role in separation than does the proximal side. The possible roles of degrading enzymes, hormones and isozymes in three segments during ethylene-induced abscission of tomato pedicel explants are discussed.     

Ethylene responsiveness changes in Pelargonium×domesticum florets

Florets of Pelargonium x domesticum L. H. Bailey respond to ethylene with rapid petal abscission. Florets become increasingly responsive to ethylene with age, with the greatest change in responsiveness occurring between the day of anthesis and 2 days later. The ethylene responsiveness coefficient (the ratio of the concentrations of ethylene giving 90% and 10% abscission) declined from 21 in 1-day-old florets to slightly greater than 1 in older florets; therefore abscission was ultraresponsive (responsiveness coefficient <81) even in 1-day old florets. Younger florets required a higher concentration of ethylene and longer duration of ethylene exposure to induce the abscission response. Even florets aged 2–3 days after anthesis required at least 40 min of exposure to ethylene for the abscission response to occur, irrespective of the concentration.     

Acclimation of crown structure to drought in Quercus robur L.—intra- and inter-annual variation of abscission and traits of shed twigs

In pedunculate oak (Quercus robur L.) the architecture of the crown is strongly influenced by age and vigour of the tree. In old oak trees cladoptosis is a major mechanism on the transformation of crown architecture. Although it can be seen quite regularly, the causes and timing of shedding of twigs as well as the quantity of affected branches remain unclear. Because abscission is often used as an indicator of reduced vigour or stress in the assessment of stand and ornamental tree health, it deserves detailed investigation, especially in the context of oak decline. We studied the inter- and intra-annual variation of abscission in six stands across the eastern part of Germany in order to identify possible triggering events and controlling factors of abscission.On average, the number of twigs abscised per year increased from 1999 to 2001. While in 1999 approximately 100 abscised twigs per m² per year were shed, this number increased to 250 per m² in 2001. The majority of twigs was actively shed, a significant proportion of the remaining twigs was partly abscised. Only a small part of the abscised twigs had leaves attached to them. From June to September 20 per cent of the twigs had leaves, in the remaining months of the year less than 10 per cent.The analysis of almost 30,000 twig fragments over the course of 3 years demonstrated at least partial control by the tree of the process of abscission. The loss of the terminal bud and the formation of a male flower are traits correlated with abscission.Our data do not support the widely held belief that cladoptosis is mainly an immediate reaction to drought stress that reduces transpiring leaf area. The proportion of leafy twigs was quite low and the main peak of abscission occurred in late autumn, thus having little immediate effect on transpiration. In addition, we observed a time lag of 3 weeks between the onset of drought stress and increased levels of abscission.     

Relationship between petal abscission and programmed cell death in <Emphasis Type="Italic">Prunus yedoensis</Emphasis> and <Emphasis Type="Italic">Delphinium belladonna</Emphasis>

Depending on the species, the end of flower life span is characterized by petal wilting or by abscission of petals that are still fully turgid. Wilting at the end of petal life is due to programmed cell death (PCD). It is not known whether the abscission of turgid petals is preceded by PCD. We studied some parameters that indicate PCD: chromatin condensation, a decrease in nuclear diameter, DNA fragmentation, and DNA content per nucleus, using Prunus yedoensis and Delphinium belladonna which both show abscission of turgid petals at the end of floral life. No DNA degradation, no chromatin condensation, and no change in nuclear volume was observed in P. yedoensis petals, prior to abscission. In abscising D. belladonna petals, in contrast, considerable DNA degradation was found, chromatin was condensed and the nuclear volume considerably reduced. Following abscission, the nuclear area in both species drastically increased, and the chromatin became unevenly distributed. Similar chromatin changes were observed after dehydration (24 h at 60°C) of petals severed at the time of flower opening, and in dehydrated petals of Ipomoea nil and Petunia hybrida, severed at the time of flower opening. In these flowers the petal life span is terminated by wilting rather than abscission. It is concluded that the abscission of turgid petals in D. belladonna was preceded by a number of PCD indicators, whereas no such evidence for PCD was found at the time of P. yedoensis petal abscission. Dehydration of the petal cells, after abscission, was associated with a remarkable nuclear morphology which was also found in younger petals subjected to dehydration. This nuclear morphology has apparently not been described previously, for any organism.