Allometric co-variation of xylem and stomata across diverse woody seedlings

Leaf stomatal density is known to co-vary with leaf vein density. However, the functional underpinning of this relation, and how it scales to whole-plant water transport anatomy, is still unresolved. We hypothesized that the balance of water exchange between the vapour phase (in stomata) and liquid phase (in vessels) depends on the consistent scaling between the summed stomatal areas and xylem cross-sectional areas, both at the whole-plant and single-leaf level. This predicted size co-variation should be driven by the co-variation of numbers of stomata and terminal vessels. We examined the relationships of stomatal traits and xylem anatomical traits from the entire plant to individual leaves across seedlings of 53 European woody angiosperm species. There was strong and convergent scaling between total stomatal area and stem xylem area per plant and between leaf total stomatal area and midvein xylem area per leaf across all the species, irrespective of variation in leaf habit, growth-form or relative growth rate. Moreover, strong scaling was found between stomatal number and terminal vessel number, whereas not in their respective average areas. Our findings have broad implications for integrating xylem architecture and stomatal distribution and deepen our understanding of the design rules of plants' water transport network.     

A comparison of two methods for measuring vessel length in woody plants

Vessel lengths are important to plant hydraulic studies, but are not often reported because of the time required to obtain measurements. This paper compares the fast dynamic method (air injection method) with the slower but traditional static method (rubber injection method). Our hypothesis was that the dynamic method should yield a larger mean vessel length than the static method. Vessel length was measured by both methods in current year stems of Acer, Populus, Vitis and Quercus representing short‐ to long‐vessel species. The hypothesis was verified. The reason for the consistently larger values of vessel length is because the dynamic method measures air flow rates in cut open vessels. The Hagen–Poiseuille law predicts that the air flow rate should depend on the product of number of cut open vessels times the fourth power of vessel diameter. An argument is advanced that the dynamic method is more appropriate because it measures the length of the vessels that contribute most to hydraulic flow. If all vessels had the same vessel length distribution regardless of diameter, then both methods should yield the same average length. This supports the hypothesis that large‐diameter vessels might be longer than short‐diameter vessels in most species.     

正廿面体病毒的三角形剖分数和壳粒数公式的推导

本文对p=h~2+hk+k~2,T=pf~2,C=10T+2和C=10p(n-1)~2+2几个公式进行了新的推导和计算,并对其公式间的关系和每个参数的数学含义作了说明,进而澄清了一些模糊认识,加深了对公式的理解和运用。     

磁共振血管造影对颈部静脉系统疾病诊断的应用价值

目的：探讨三维动态增强磁共振血管成像（30 DCE MRA）对于颈部静脉系统疾病的临床应用价值。方法：对7例疑有颈部静脉病变的病人进行了3D DCE MRA检查,观察对病变血管及正常血管显示情况。结果：7例检查图像都能清晰显示正常血管结构及病变情况。其中2例正常,2例颈静脉血栓,1例颈静脉癌栓,1例颈静脉扩张,2例动静脉瘘。所有病例均经手术及（或）DSA证实。结论：3D DCE MRA是一种简便,易行,有效的血管检查方法,分辨率高,假阳性率低,在临床上已广泛应用,但临床上多限于动脉系统疾病的诊断。只要选择合适的序列、扫描时间及对比剂的剂量就能较好显示静脉血管情况。此项技术的应用,在颈部静脉病变诊断中有很大的实用价值。     

Structural determinants of increased susceptibility to dehydration‐induced cavitation in post‐fire resprouting chaparral shrubs

It is well established that transpiration and photosynthetic rates generally increase in resprouting shoots after fire in chaparral shrublands. By contrast, little is known about how plant hydraulic function varies during this same recovery period. We hypothesized that vascular traits, both functional and structural, would also shift in order to support this heightened level of gas exchange and growth. We examined stem xylem‐specific hydraulic conductivity (K_s) and resistance to cavitation (P₅₀) for eight chaparral shrub species as well as several potential xylem structural determinants of hydraulic function and compared established unburned plants and co‐occurring post‐fire resprouting plants. Unburned plants were generally more resistant to cavitation than resprouting plants, but the two groups did not differ in K_s. Resprouting plants had altered vessel structure compared with unburned plants, with resprouting plants having both wider diameter vessels and higher inter‐vessel pit density. For biomechanics, unburned plants had both stronger and denser stem xylem tissue than resprouting plants. Shifts in hydraulic structure and function resulted in resprouting plants being more vulnerable to dehydration. The interaction between time since disturbance (i.e. resprouting versus established stands) and drought may complicate attempts to predict mortality risk of resprouting plants.     

How weak twining lianas adapt to competition with host tree trunks: Case of Merremia boisiana

Fierce competition exists between most stem‐twining lianas and the trunks of host trees. However, Merremia boisiana, a vigorous invasive twining liana, never strangles the host tree. Here, we investigated how M. boisiana stems adjust their twining growth to avoid intense competition with host trees, and how hydraulic conductivity is maintained for rapid asexual reproduction. We evaluated the effects of competition on twining M. boisiana stems (E_m) and host tree trunks (E_h), compared differences in secondary growth between twining and creeping M. boisiana stems, calculated the total number of vessels (N_t), vessel density (Vmm⁻²), average vessel diameter (VD_ave), and percentage of vessels wider than 300 μm in diameter (P₃₀₀) in the secondary xylem, and traced how these parameters change with increasing cross‐sectional area of stem (SA). The results showed that twining M. boisiana stems were competitively weaker, and mean E_m (14.3%) was 21 times greater than that of E_h (0.7%). Secondary growth along the normal direction of the contact surface was significantly inhibited in stems twining on host trees. The lateral secondary growth of these stems was active, forming secondary vascular rings and/or arcs with abundant large vessels. Secondary growth in the central vascular cylinder was also significantly limited in extremely flat twining stems. N_t was positively and linearly correlated with SA. Vmm⁻² and VD_ave fluctuated greatly in younger stems and tended to be stable in older stems. N_t and Vmm⁻² did not significantly differ between twining and creeping stems, while VD_ave and P₃₀₀ were both higher in twining stems compared to creeping stems of the same size. In conclusion, well‐developed lateral anomalous secondary growth prevents twining M. boisiana stems from fiercely competing with their host trees, while stable vessel density and wider, newly formed, vessels ensured sufficient hydraulic conductivity for the rapid asexual reproduction of twining M. boisiana stems.     

血管内皮生长因子受体3在大鼠胚胎皮肤淋巴管和血管内皮的表达及意义

目的观察血管内皮生长因子受体3(vascular endothelial growth factor receptor-3, VEGFR-3)蛋白在大鼠第15d胚胎和第21d胚胎皮肤淋巴管和血管内皮的表达水平,探讨VEGFR-3在胚胎淋巴管和血管发生发育中的生物功能.方法应用免疫组织化学技术(SABC法)对大鼠第15d和第21d胚胎共61例皮肤样本进行抗鼠VEGFR-3免疫组织化学染色,观察VEGFR-3在皮肤淋巴管和血管内皮细胞的表达情况.结果大鼠胚胎皮肤淋巴管和血管内皮细胞均阳性表达VEGFR-3蛋白,VEGFR-3蛋白在大鼠胚胎第15d、胚胎第21d皮肤淋巴管内皮细胞的阳性表达率分别是38.71%(12/31)和73.33%(22/30),第21d胚胎皮肤淋巴管VEGFR-3蛋白的表达水平明显高于第15d胚胎皮肤淋巴管VEGFR-3蛋白的表达水平(P<0.01).VEGFR-3蛋白在大鼠胚胎第15d、胚胎第21d皮肤血管内皮细胞的阳性表达率分别是48.39%(15/31)和46.67%(14/30),第15d和第 21d胚胎皮肤血管VEGFR-3蛋白的表达水平之间无明显差异(P>0.05).结论随着大鼠胚胎的发育,VEGFR-3蛋白在皮肤淋巴管的表达水平表现为明显上升的趋势,提示VEGFR-3在淋巴管发生发育中的作用逐渐增强.     

Prevention of Vessel-Source Marine Pollution: A Note on the Challenges and Prospects for Chinese Practice Under International Law

This article examines China's domestic legal regime for the prevention of vessel source pollution. It pays special attention to the recently adopted Regulation on Prevention and Control of Marine Pollution from Vessels. Potential challenges and emerging issues that China has to confront are addressed, including: application of the legislation to disputed sea areas between China and its neighbors, freedom of navigation in the exclusive economic zone, reduction of emission from ships, and prevention of invasive species from ballast water.     

氨基酸对心血管功能的影响

介绍了氨基酸对心血管功能的保护作用,氨基酸不仅可减轻心肌在缺血再灌注、心力衰竭和心肌梗塞中的损伤,而且对血压、血脂和心律失常也有一定的调节作用。     

6种1变种猕猴桃植物染色体数目的研究

报道了猕猴桃属６种１变种细胞染色体数目,表明湖北猕猴桃、激光猕猴桃、黄毛猕猴桃为二倍体,２ｎ＝２ｘ＝５８;大花猕猴桃为四倍体,２ｎ＝４ｘ－１１６,绿果猕猴桃（美味猕猴桃的１个变种）为种倍体,染色体数目２ｎ＝４ｘ－１１６,以上均为首次报道。并再次证实ｘ＝２９应是本属染色体数目的基础,狗枣猕猴桃和阔叶猕猴桃二倍体类型２＝５８。     

“x” is not a bias,but a number with real biological significance

Recent literature criticized the use of the symbol “x” to denote basic chromosome number in cytotaxonomy. I show here that this criticism is superfluous and is based on historical confusion between the concepts of basic chromosome number (or monoploid chromosome number), which is objective, and ancestral basic chromosome number, which is always inferred, by means of several – more or less reliable – methods. The most relevant literature is discussed and, in the end, I propose the use of x for basic chromosome number and p for (hypothetical) ancestral basic chromosome number.     

中国鲤形目鱼类的中轴骨骼数及其生态适应性

为探讨中国鲤形目鱼类中轴骨骼数及其与系统发育和生态习性的相关性,采用X光透视照相法对157种鲤科(Cyprinidae)、鳅科(Cobitidae)、平鳍鳅科(Balitoridae)鱼类的脊椎骨数、肋骨数、尾椎数进行了比较分析。结果显示,中国鲤形目鱼类的脊椎骨数在30-52枚之间,均值39.45?4.44;肋骨数在8-28对之间,均值15.27?3.08;尾椎数在14-34枚之间,均值21.08?2.89。依据脊椎骨数、肋骨数、尾椎数对鲤科各亚科进行聚类,显示鲤科12个亚科分为2大类：雅罗鱼类,包括雅罗鱼亚科、鲌亚科、鲴亚科、裂腹鱼亚科等4亚科;鲃类,包括鲢亚科、鮈亚科、鱼丹亚科、鲃亚科、野鲮亚科、鳅鮀亚科、鲤亚科、鱊亚科等8亚科。单因素方差分析显示,鲤科肉食性鱼类的肋骨数与脊椎骨数的比值显著少于植食性鱼类(P＜0.05),而脊椎骨数、尾椎数则显著多于植食性鱼类(P＜0.05)。中上层鱼类的脊椎骨数、尾椎数显著多于下层鱼类(P＜0.05)。极小型鱼类的脊椎骨数、肋骨数,以及肋骨数与脊椎骨数之比显著少于大型鱼类(P＜0.05)。表明鲤科鱼类的中轴骨骼数与其系统发育和生态习性及体型具有明显的相关性。     

国产十四种苋属植物的染色体数目

报道了国产14种苋属植物的染色体数目。部分种的染色体数目为2n=34,即反枝苋Amaranthus retroflexus,刺苋A．spinosus,红苋A．cruentus,腋花苋A．roxburghianus,合被苋A．polygonoides,皱果苋A． viridis,凹头苋A．lividus,苋A．tricolor。其他种的染色体数目为2n=32,即尾穗苋A．caudatus,绿穗苋A． hybridus,千穗谷A．hypochendriacus,繁穗苋A．paniculatus,北美苋A．blitoides,白苋A．albus。其中腋花 苋的染色体数目为首次报道。该属染色体基数为x=16,17。两种染色体基数在苋属2个组(sect．Ama- ranthus和sect．Blitopsis)中均存在。由于苋属植物染色体大多为小型染色体,因此对苋属植物目前尚不 能进行详尽的核型分析。     

黑龙江槭树属植物导管分子解剖学研究

利用扫描电子显微镜,通过管道铸型技术,对黑龙江槭树科（Aceraceae）槭树属（Acer Linn.）中8种植物导管分子的微形态结构进行了比较研究。结果表明：该属植物导管分子长度,除白牛槭 （Acer mandshurica Maxim.）较长外,其余植物种类导管分子长度在133.00～187.50 μm;导管管腔宽度,在17.06～28.00 μm之间;纹孔排列方式以对列式、互列式单独存在,或以两者形式并存;管间纹孔成群分布且大部分呈现一定形状;讨论了导管分子管腔的主要特征及其与生境的关系。     

Carbon dioxide and ethylene evolution in the culture atmosphere of Magnolia cultured in vitro

Subcultured explants of Magnolia soulangeana Soul, were incubated in tissue culture containers fitted with different types of closures. Type of closure affected the CO₂ concentration, with levels as high as 14% CO₂ being detected. The ethylene concentration increased gradually with time, to as much as 2–3 ppm after 9 weeks. There was a large variation in the composition of the atmosphere within the containers of any one type. The way by which a container was closed influenced exchange of the inner gas phase with the surrounding atmosphere and was important in determining the development of the cultured tissues.     

中亚热带喀斯特常绿落叶阔叶混交林典型树种的木质部解剖与功能特征分析

树木木质部主要由导管、纤维和薄壁组织组成, 分别具有运输、支撑和贮存的生理功能。由于木质部空间限制, 一种组织比例的增加会导致其他组织比例的降低, 因而可能表现出权衡关系。分析木质部组织比例和权衡关系有助于了解植物的生理生态适应性。该研究选择中亚热带喀斯特常绿落叶阔叶混交林21种典型树种(10种落叶树种, 11种常绿树种), 测定枝条木质部各组织比例, 计算水力相关指标并分析性状之间的相关性。结果表明: (1)与全球木质部解剖数据对比分析, 喀斯特树种木质部趋向具有较高比例的薄壁组织; (2)喀斯特树种导管组织比例与薄壁和纤维组织比例之间没有显著的相关性, 但是薄壁和纤维组织比例之间有显著的权衡关系; (3)常绿和落叶树种的木质部水力运输安全性(导管壁加固系数)和效率性(理论导水率)均具有显著的权衡关系, 但是这两个类群线性回归的截距存在显著差异, 即在相同的理论导水率条件下, 落叶树种比常绿树种具有较高的导管壁加固系数(安全性), 可能与常绿树种具有更多的轴向薄壁组织有关。喀斯特树种木质部解剖特征表明薄壁组织的贮存功能对喀斯特树种(尤其是常绿树种)的干旱适应具有重要作用。     

余甘子次生木质部导管分子观察研究

运用细胞图象分析系统及显微照相的方法,对余甘子次生木质部导管分子进行观察研究.结果发现,余甘子次生木质部导管分子中存在着许多不同的样式,导管分子大多数具尾;其穿孔板存在着两种类型:(1)两端均为1个单穿孔板;(2)一端为1个单穿孔板另一端为2个单穿孔板;(3)极少数的导管分子具有特殊的内含物;(4)管间纹孔式为互列纹孔式;(5)导管射线间纹孔式为混合型纹孔与横列刻痕状纹孔以及梯状穿孔.     

三段移床法Smart——Prep CeMRA在下肢动脉血管病变中的应用

探讨三段移床法智能跟踪对比增强磁共振血管造影(Smart-prep contrast enhanced magnetic resonance angiography,简称Smart-Prep CeMRA)在检查下肢血管性病变的方法和效果。材料和方法采用GESignatwin exciteⅡ型1,5T磁共振扫描仪对46例临床怀疑下肢动脉及其分支血管疾病进行三段移床法Smart-PrepCeMRA检查。结果 全部病例均获得清晰的下肢动脉及其主要分支血管造影图像。结论 采用Smart-PrepCeMRA能清晰显示下肢动脉及其分支血管图像,具有很好的临床应用价值。     

用树脂铸型法研究4种植物木质部导管结构

导管的大小、形态和彼此连接方式的不同对水分运输和应力支撑有重要作用。本研究采用树脂铸型法对毛白杨(Populus tomentosa Carr)、旱柳(Salix matsudana)、榆树(Ulmus pumila L.)和紫藤(Wisteria sinensis)4个树种的导管分子三维结构进行比较研究,分析导管结构特征和其水分输运的关系。导管内壁结构被印在铸型的表面上,将铸型放在扫描电子显微镜下观察。结果表明：旱柳和毛白杨的导管分子特征较接近,与榆树和紫藤存在明显差异,相对于榆树和紫藤较原始。毛白杨和旱柳的导管分子长、侧壁纹孔少,有利于水分的输运。榆树和紫藤的导管分子相对宽,穿孔板几乎平直,更加利于水分的输运。榆树和紫藤的细导管分子有螺纹加厚,可增加导管的机械强度,减少管内产生空穴化的风险,从而保证水分更有效的运输。     

Microscopic anatomy of the thin-walled vessels leaving the heart of the lobster Homarus americanus: anterior median artery

Abstract. The anterior median artery is an unpaired vessel that leaves the anterior end of the lobster ( Homarus americanus ) heart and supplies hemolymph to the brain, the antennae, and the eyestalks. This vessel has a trilaminar organization, consisting of a tunica interna with elastic fibrils, a tunica intermedia represented by a bilayered cell mass, and a tunica externa with collagen fibrils. The exposed ends of the medial cells in the tunica intermedia exhibit small, diffuse bundles of microfilaments that are penetrated by microtubules. These bundles have a circumferential or a slightly oblique orientation relative to the lumen of the vessel. The precise role of the microfilaments is unresolved. If the irregularly shaped bundles are static structures, they might contribute to the non-linear elasticity of the artery. Alternatively, if they generate force, a coordinated contraction of the medial cells might reduce the luminal diameter of the artery and, thus, retard hemolymph flow. Microfilaments of the medial cells anchor to subplasmalemmal filamentous mats, some of which are integral to intermediate junctions and some of which are associated with unbounded cell membranes (hemi-intermediate junctions). Contraction of the microfilament-bearing cells would have to occur without the benefit of nervous innervation or the participation of communicating (gap) junctions. If cell contractility is confirmed, a reclassification of the anterior median artery, from capacitance vessel to resistance vessel, is in order, and the bilayered cell mass in the tunica intermedia would likely qualify as the first unstriated muscle found in crustaceans.