Biomechanics of Isolated Plant Cuticles

The mechanical properties of isolated cuticles of leaves (Yucca aloifolia, Clusia fluminensis, Nerium oleander, Hedera helix) and one fruit (Lycopersicon esculentum) were investigated by means of a tensile test. Samples of the leaves and the fruit were cut to identical size (12.5 × 50 mm) and the cuticles were enzymatically isolated, cleaned, and air dried. The morphology of the isolated cuticular membranes (CM) was investigated by scanning electron microscopy (SEM) and showed considerable differences. The thickness of the CM was determined by a digital image analysis system and ranged between 2.4 and 13.4 μm. The CM were subjected to a tensile test and the results are presented as stress-strain diagrams. From the latter, Young's moduli were calculated, a measure for the stiffness which allows the direct comparison of different materials. The obtained values ranged between 0.1 and 1.3 CPa. Hydration of CM caused a decrease of Young's moduli of about 35–50%. A possible role of the cuticle as a factor for the stabilization of plant organs is discussed.     

一种新型生物聚合物Ss的流变学性质及成胶特性

本文对一种新型生物聚合物Ss的流变学性质及成胶特性进行了研究。该聚合物的流变学性质与黄原胶类似, 具有高粘性、假塑性及耐盐性。0.6％以上的Ss溶液加热(≥75℃)并冷却至室温可形成凝胶, 加入金属离子可以改变其成胶所需的最低聚合物浓度及所成凝胶的性质。利用质构分析(TPA)方法, 研究了不同聚合物浓度和钙离子浓度下凝胶的质构性质。钙离子的加入能促进凝胶的形成, 凝胶的硬度、弹性、内聚性随聚合物浓度及钙离子浓度的增加而增大, 但大于最适钙离子浓度时, 硬度、弹性及内聚性均有所下降。     

一种新型生物聚合物Ss的流变学性质及成胶特性

本文对一种新型生物聚合物ss的流变学性质及成胶特性进行了研究.该聚合物的流变学 性质与黄原胶类似,具有高粘性、假塑性及耐盐性.0.6%以上的Ss溶液加热(≥75℃)并冷却至室温可形成凝胶,加入金属离子可以改变其成胶所需的最低聚合物浓度及所成凝胶的性质.利用质构分析(TPA)方法,研究了不同聚合物浓度和钙离子浓度下凝胶的质构性质.钙离子的加入能促进凝胶的形成,凝胶的硬度、弹性、内聚性随聚合物浓度及钙离子浓度的增加而增大,但大于最适钙离子浓度时,硬度、弹性及内聚性均有所下降.     

中国华夏植物区二叠纪几种科达植物分散角质层及其意义

中国华夏植物区科达植物的研究历史虽然最早可上溯至1883年,但直到1991年才首次报道其角质层构造。到目前为止,中国华夏植物区总共描述了4种科达植物原位角质层和3种分散角质层。但与欧美植物区相比,有关中国华夏植物区科达植物角质层的研究工作还较薄弱。本文较详细地描述了3种产自中国华夏植物区二叠纪煤系地层中的科达植物分散角质层。其中2种采自华北亚区南缘的安徽淮南新庄孜矿山西组A1煤顶板,地质时代为早二叠世;另一种采自华南亚区的贵州水城矿区大河边矿龙潭组顶部的11号煤层,地质时代为晚二叠世早期。将这3种科达植物分散角质层与已知的欧美植物区和中国华夏植物区的种类进行了对比,认为它们都是新的类型。讨论了这3种新的科达植物分散角质层所具有的古植物学意义。     

中国华夏植物区二叠纪几种科达植物分散角质层及其意义

中国华夏植物区科达植物的研究历史虽然最早可上溯至1883年,但直到1991年才首次报道其角质层构造.到目前为止,中国华夏植物区总共描述了4种科达植物原位角质层和3种分散角质层.但与欧美植物区相比,有关中国华夏植物区科达植物角质层的研究工作还较薄弱.本文较详细地描述了3种产自中国华夏植物区二叠纪煤系地层中的科达植物分散角质层.其中2种采自华北亚区南缘的安徽淮南新庄孜矿山西组A1煤顶板,地质时代为早二叠世;另一种采自华南亚区的贵州水城矿区大河边矿龙潭组顶部的11号煤层,地质时代为晚二叠世早期.将这3种科达植物分散角质层与已知的欧美植物区和中国华夏植物区的种类进行了对比,认为它们都是新的类型.讨论了这3种新的科达植物分散角质层所具有的古植物学意义.     

Impact of the extrusion process on xanthan gum behaviour

Processing xanthan gum by extrusion and subsequent drying produces a biopolymer showing particulate, rather than molecular behaviour in aqueous solution. This form of xanthan disperses very readily to give a viscosity that is strongly dependent on salt concentration. On heating above the temperature of the order-disorder transition as determined by calorimetry, there is a viscosity transition that is indicative of the irreversible loss of the particulate structure. It is suggested that the extrusion process melts and aligns xanthan macromolecules. On cooling reordering will occur but in the highly concentrated environment in the extruder ( approximately 45% water w/w), inter-molecular association between neighbouring macromolecules cannot proceed to completion due to kinetic trapping. As a consequence a network structure is created maintained by associations involving ordered regions. A xanthan solution can be prepared from this particulate material by dispersing and subsequent heating far more readily than can be achieved with non-processed xanthan.     

SEM Observation on the Structure of Cuticles on Leaf Inner Surface of Abies (Pinaceae) and Its Significance in Systematics

Comparative investigation of the inner surface of the needle cuticle of 36 species and 2 varieties of Abies under SEM has revealed that the characteristics of the intercellular flanges are rather distinct and four types can be distinguished: (1) Straight and developed single flange. This type is only represented by Abies bracteata D. Don. Morphologically, this species is also quite unique in the genus Abies and was once treated as a subgenus by Franco and Liu. Its special structure of the leaf cuticle observed here seems to support their treatment. (2) Double flanges. This type was first discovered in a leaf fossil of Abies from England. In modern plants of Abies, it is found only in the species from Central America. (3) Undeveloped single flange. This type is represented by a small group of Abies from the west and east coastal area of the Pacific Ocean. (4) Undulate and developed single flange. This type is represented by most of the species of Abies, including all the species in Europe and most species in Asia and North America. The flange types mentioned above seem to have some relationships with the geographical distribution of the species in the genus Abies, and their occurrence might have not been completely influenced by the habitats, hence the features of the intercellular flanges may provide good evidence for the subgeneric division of Abies. Based on our results and those from the previously published literature about the infrageneric treatments of Abies and the distribution of the fossils, we consider that western North America might be the diversity center of modern Abies. Florin once pointed out that the characters of the leaf cuticle in gymnosperms are of great significance for the generic andinfrageneric division. This viewpoint is strongly supported by our study on modern Abies.     

植物器官大小相关基因研究进展

器官大小是植物形态的一个重要特征,而且具有严格的种属特异性。植物器官大小虽然受到外在的环境因素（如光照、营养等）的影响,但它由内在特有的细胞数目和细胞大小决定。许多通过转录调节、蛋白合成、激素调节或松弛细胞壁等途径作用于植物细胞繁殖和/或细胞扩张的基因已经被鉴定,它们的过表达或缺失表达能促进植物器官大小和加快植物生长。尽管如此,这些基因通过相对独立的途径起作用,在植物中难以阐明一个相对整合的器官大小基因调控网络,这也是该研究领域的亟待需要解决的问题。目前,一些器官大小相关基因已经应用农作物育种,并培育出显著增大的农作物品种,这也证实了利用器官大小基因进行植物品种选育的可行性。因此,通过研究药用植物器官大小的基因,人为地在分子水平上有目的的调控器官的大小和形态,是缓解当前许多药用植物面临的资源紧缺、枯竭濒危困境的可考虑途径之一。     

Temperature and the Growth of Plant Cells

In cell elongation, the juvenile cell vacuolates, takes up water, and expands by irreversible extension of the growth-limiting primary walls. This process was elaborated analytically by Lockhart in the mid-1960s. His growth equation does not, however, include the influence of the environmental temperature at which cell growth takes place. In this article we consider a phenomenological model including temperature in the equation of growth. Also, by introducing the possible influence of growth regulators treated here as external perturbations, linear and nonlinear solutions are found. A comparison of experimental and theoretical results permits qualitative and quantitative conclusions concerning change in the magnitude of the cell wall yielding coefficient Φ as a function of both time and temperature (with or without external perturbations), which has acquired reasonable values throughout.     

若干植物分类学术语介绍及中译名商榷

为便于国内外植物分类学同行的交流,本文介绍了48个国内尚未收入的植物分类学术语,提出了建议的中译名,并对10个巳有术语的定义和中译名等问题进行了讨论。     

安徽蔷薇属植物资源及其开发利用

通过大量的实地调查、查阅文献和腊叶标本,初步查清了安徽蔷薇属植物资源,约有13种,9变种和2型.同时,列出了其主要分布地;阐述了其生物学特性、经济价值及开发利用的现状和途径.     

Plant development scores from fixed-date photographs: the influence of weather variables and recorder experience

In 1944, John Willis produced a summary of his meticulous record keeping of weather and plants over the 30 years 1913–1942. This publication contains fixed-date, fixed-subject photography taken on the 1st of each month from January to May, using as subjects snowdrop Galanthus nivalis, daffodil Narcissus pseudo-narcissus, horse chestnut Aesculus hippocastanum and beech Fagus sylvatica. We asked 38 colleagues to assess rapidly the plant development in each of these photographs according to a supplied five-point score. The mean scores from this exercise were assessed in relation to mean monthly weather variables preceding the date of the photograph and the consistency of scoring was examined according to the experience of the recorders. Plant development was more strongly correlated with mean temperature than with minimum or maximum temperatures or sunshine. No significant correlations with rainfall were detected. Whilst mean scores were very similar, botanists were more consistent in their scoring of developmental stages than non-botanists. However, there was no overall pattern for senior staff to be more consistent in scoring than junior staff. These results suggest that scoring of plant development stages on fixed dates could be a viable method of assessing the progress of the season. We discuss whether such recording could be more efficient than traditional phenology, especially in those sites that are not visited regularly and hence are less amenable to frequent or continuous observation to assess when a plant reaches a particular growth stage.     

Hydration and tissue solid content of the lean body on prolonged exposure to altitude

Using densitometric, hydrometric and anthropometric techniques, body fat, tissue solids, water and mineral content were quantitatively measured on two groups each of 26 young and healthy Indian soldiers of mixed ethnic composition. The experimental group was exposed to 3500 m altitude for 2 years and the experiments were carried out after 48 h and 3 weeks rehabilitation in Delhi (300 m). The control group was never exposed to high altidues. Inspite of the experimental group being fed with superior rations at high altitude, this group showed significantly hyperhydrated lean body with reduced tissue solids in comparison to the control group which was fed with identical rations in Delhi. The calculated mean density of the fat free body had declined to 0.092×10³ kg/m³. The 3 week stay at low altitude had little influence on body composition. Hyperhydration, with reduced tissue solids, would cause reduction in the density of fat free body, and would thus interfere with the estimates of total body fat based on densitometric procedures alone. In the hyperhydrated state, Siri's formula overestimated fat by 22.8% of the true value.This paper was presented in part at the National Symposium on Stress Physiology held in New Delhi during Oct. 23–25, 1986.     

作物生长温度效应的非线性模型及其比较研究

通过严密的数学证明,发现了前人关于作物生长温度效应非线性模型之间的内在联系,修正了有关学者对模型参数定义的局限性,提出了一个通用的作物生长温度效应非线性模型,本研究还将该模型与笔者最近提出的基于高斯方程的非线性模型进行了比较研究,介绍了应用SAS软件求取两个模型相关参数的方法,并以马铃薯生育期模拟为例进行了实证研究,表明这两个模型均有良好的适用性。     

植物反转录转座子及其在功能基因组学中的应用

高等植物中的反转录转座子是构成植物基因组的重要成分之一.它分病毒家族和非病毒家族两类,病毒家族包括反转录病毒和类似于反转录病毒的非病毒转座子,病毒家族中的反转录转座子可再细分为Ty3-gypsy类和Ty1-copia类;非病毒家族可细分为LINE类和SINE类.正常情况下大部分反转录转座子不具有活性,某些生物或非生物因素胁迫可激活部分反转录转座子转座.反转录转座子自身编码反转录酶进行转录,以"拷贝-粘贴"的转座模式导致基因组扩增和进化.具有活性的反转录转座子通过插入产生新的突变,可作为一种基因标签技术,应用于功能基因组学研究,并成为研究植物基因功能和表达的重要技术平台.本文综述了近几年来在植物反转录转座子方面的研究进展,主要包括植物反转录转座子的结构、特征、活性及其对基因组的影响和它们在功能基因组学中的应用.     

温度对草鱼出血病影响的初步探讨

将鱼呼肠孤病毒(FRV)感染的草鱼饲养在人工控温的水族箱内,水温在24—30℃恒温时其死亡率无显著差异(P>0.05),而在20℃和33℃恒温时死亡率则明显降低,与24℃—30℃恒温相比死亡率有非常显著差异(P<0.01)。人工感染恒温饲养期间,死亡高峰期随水温降低而推迟,缓慢改变水温能降低死亡率,在低于20℃攻毒并维持一星期左右,即使逐步升温至30℃也不会导致感染鱼的大批死亡。     

Hydration valve controlled non-selective conduction of Na and K in the NaK channel

The Na⁺ and K⁺ channels are essential to neural signaling, but our current knowledge at the atomic level is mainly limited to the conducting mechanism of K⁺. Unlike a K⁺ channel having four equivalent K⁺-binding sites in its selectivity filter, a NaK channel has a vestibule in the middle part of its selectivity filter, and can conduct both Na⁺ and K⁺ ions. However, the underlying mechanism for non-selective ion conduction in NaK remains elusive. Here we find four small grottos connecting with the vestibule of the NaK selectivity filter, which form a vestibule-grotto complex perpendicular to the filter pore with a few water molecules within it. It is shown that two or more of the water molecules coming to the vestibule to coordinate the cation are necessary for conducting both Na⁺ and K⁺ ions, while only one water molecule in the vestibule will obstruct ion permeation. Thus, the complex with the aid of interior water movement forms a dynamic hydration valve which is flexible in conveying different cations through the vestibule. Similar exquisite hydration valve mechanisms are expected to be utilized by other non-selective cation channels, and the results should shed new light on the importance of water in neural signaling.     

Effects of Hydration Level and Heat Stress on Thermoregulatory Responses,Hematological and Blood Rheological Properties in Growing Pigs

Heat stress is one of the major limiting factors of production efficiency in the swine industry. The aims of the present study were 1) to observe if hemorheological and hematological parameters could be associated to physiological acclimation during the first days of heat stress exposure and 2) to determine if water restriction could modulate the effect of thermal heat stress on physiological, hematological and hemorheological parameters. Twelve Large White male pigs were divided into an ad libitum and a water restricted group. All pigs were submitted to one week at 24°C (D-7 to D-1). Then, at D0, temperature was progressively increased until 32°C and maintained during one week (D1 to D7). We performed daily measurements of water and feed intake. Physiological (i.e., skin temperature, rectal temperature, respiratory rate), hematological and hemorheological parameters were measured on D-6, D-5, D0, D1, D2 and D7. Water restriction had no effect on physiological, hematological and hemorheological parameters. The first days of heat stress caused an increase in the three physiological parameters followed by a reduction of these parameters suggesting a successful acclimation of pigs to heat stress. We showed an increase in hematocrit, red blood cell aggregation and red blood cell aggregation strength during heat stress. Further, we observed an important release of reticulocytes, an increase of red blood cell deformability and a reduction of feed intake and blood viscosity under heat stress. This study suggests that physiological acute adaptation to heat stress is accompanied by large hematological and hemorheological changes.