长白鱼鳞云杉木材纹孔塞不同位置对渗透性的影响

通过对长白鱼鳞云杉（Picea jezoensis var.komarovii(V.Vassi.)Cheng et L.K.Fu)生材分别进行气干处理和酒精置换处理以及对其气干材进行水浸后再用酒精置换处理,研究了此３种处理方法形成不同的纹孔塞位置对木材渗透性的影响。结果表明,为材和心材的生材经气干处理后,其中边材的早材和晚材纹孔闭塞率增加至９９％和８１％,而心材因为其纹孔塞在立木时就已发生偏移,其早材和晚材纹孔闭塞率亦高,分别为９７％和８６％;由于其绝大多数纹孔塞保持中央位置,其中边材的早材和晚材纹孔塞闭率低,分别为８％和１７％,而心材因为绝大部分纹孔在立木时即已为关闭状态,酒精置换处理以降低其闭塞率无效,故其纹孔闭塞率高,分别为９７％和８６％;此种状态下边材和心材的气体渗透性分别为１１．７１３和０．０７４darcy,比普通气干处理状态下的渗透性分别增加１０１．５倍和６２．０％,t检验表明,前差异非常显,但后差异不显,气干材经水浸处理后再用酒精置换处理,其边材的早材和晚材纹孔闭塞率分别降低了１８％和２２％,心材分别降低了０和１７％;其气体渗透性分别为０．４３９和０．０６０darcy,较处理前分别增 ８５％和４９％,t检验表明差异均显。     

Bordered pits in xylem of vesselless angiosperms and their possible misinterpretation as perforation plates

Vesselless wood represents a rare phenomenon within the angiosperms, characterizing Amborellaceae, Trochodendraceae and Winteraceae. Anatomical observations of bordered pits and their pit membranes based on light, scanning and transmission electron microscopy (SEM and TEM) are required to understand functional questions surrounding vesselless angiosperms and the potential occurrence of cryptic vessels. Interconduit pit membranes in 11 vesselless species showed a similar ultrastructure as mesophytic vessel‐bearing angiosperms, with a mean thickness of 245 nm (± 53, SD; n = six species). Shrunken, damaged and aspirated pit membranes, which were 52% thinner than pit membranes in fresh samples (n = four species), occurred in all dried‐and‐rehydrated samples, and in fresh latewood of Tetracentron sinense and Trochodendron aralioides. SEM demonstrated that shrunken pit membranes showed artificially enlarged, > 100 nm wide pores. Moreover, perfusion experiments with stem segments of Drimys winteri showed that 20 and 50 nm colloidal gold particles only passed through 2 cm long dried‐and‐rehydrated segments, but not through similar sized fresh ones. These results indicate that pit membrane shrinkage is irreversible and associated with a considerable increase in pore size. Moreover, our findings suggest that pit membrane damage, which may occur in planta, could explain earlier records of vessels in vesselless angiosperms.     

Mechanism of water‐stress induced cavitation in conifers: bordered pit structure and function support the hypothesis of seal capillary‐seeding

Resistance to water‐stress induced cavitation is an important indicator of drought tolerance in woody species and is known to be intimately linked to the anatomy of the xylem. However, the actual mechanical properties of the pit membrane are not well known and the exact mode of air‐seeding by which cavitation occurs is still uncertain. We examined the relationship between cavitation resistance and bordered pit structure and function in 40 coniferous species. Xylem pressure inducing 50% loss of hydraulic conductance (P₅₀, a proxy for cavitation resistance) varied widely among species, from ?2.9 to ?11.3 MPa. The valve effect of the pit membrane, measured as a function of margo flexibility and torus overlap, explained more variation in cavitation‐resistance than simple anatomical traits such as pit membrane, pit aperture or torus size. Highly cavitation resistant species exhibited both a high flexibility of the margo and a large overlap between the torus and the pit aperture, allowing the torus to tightly seal the pit aperture. Our results support the hypothesis of seal capillary‐seeding as the most likely mode of air‐seeding, and suggest that the adhesion of the torus to the pit border may be the main determinant of cavitation resistance in conifers.     

锌营养状况对小麦根细胞膜透性的影响

小麦缺锌不仅导致根系K~ 和NO_3~-泌出量增加,而且低分子量有机化合物如氨基酸、糖类化合物和酚类化合物的泌出量也明显提高。重新供锌(ZnSO_4)12h后,根系K~ 、NO_3~-、氨基酸和碳水化合物的泌出量迅速减少,随着时间的延长,泌出量接近对照水平。结果说明锌对根细胞膜结构的稳定性及膜功能的完整性是必不可少的。     

禾谷镰刀菌粗毒素对不同抗性水平小麦品种细胞膜透性的影响

本实验以抗、感基因型不同的6个小麦品种(系)为材料,系统研究了不同浓度的禾谷镰刀菌粗毒素胁迫处理下小麦品种(系)细胞膜透性随处理时间变化的特性.结果表明:抗、感小麦品种(系)细胞膜对外界毒素胁迫表现出敏感特性,且抗性品种(系)细胞膜对毒素的敏感性小于感病品种(系).在毒素胁迫处理72h内,随毒素处理浓度的增大和胁迫处理时间的延长,细胞膜透性增大,抗病小麦品种(系)的膜透性增量明显小于感病品种(系).胁迫处理72h抗、感小麦品种(系)的膜透性增量达到峰值,抗病品种(系)膜透性增量显著小于感病品种(系),胁迫处理72h后抗、感小麦品种(系)的膜透性增量均降低.可利用禾谷镰刀菌粗毒素胁迫处理72h的细胞膜透性增量评价小麦品种间抗病性的差异,进行抗病性鉴定.     

激光、血卟啉对小鼠S-180V肿瘤细胞膜通透性的作用及其影响因素

通过Na_2~(51)CrO_4在肿瘤细胞膜内外的分布比值的测定,观察了激光血卟啉衍生物(简称HPD)对小鼠S-180V肿瘤细胞膜通透性的作用及其影响因素:(1)通过紫外吸收光谱的测定对肿瘤细胞摄取HPD的动态过程作了观察。选择了实验所需的合适HPD浓度和作用时间,并观察到细胞悬液中血清蛋白能阻抑细胞对HPD的摄取。(2)在氦氖激光照射后即可观察到含有HPD的肿瘤细胞膜外~(51)Cr/膜内~(51)Cr的比值明显增加,而单照激光或单加HPD两组的~(51)Cr比值与正常对照组相比无明显变化。(3)上述的~(51)Cr比值变化随着照后保温时间的延长而逐渐加大。与此同时细胞形态也发生相应的变化,细胞死亡率也逐渐增加。说明除了原初的光敏反应外,还有继发的细胞损伤。(4)细胞悬液中血清蛋白的存在虽然对激光血卟啉对肿瘤细胞的杀伤作用有所减弱,但在这样条件下的光敏反应比较接近临床上治疗肿瘤的实际情况。     

Effect of Enhanced UV-B Radiation on Polyamine Content and Membrane Permeability in Cucumber Leaves

Cucumber plants (Cucumis sativus L., cv. Jingchun 3) were grown in a greenhouse under PAR illumination of 400–600 mol/(m² s) at 30/15°C (day/night) temperature. Two enhanced biologically effective UV-B radiation levels per day were applied: 8.82 kJ/m² (T₁) and 12.6 kJ/m² (T₂). Cucumber seedlings were irradiated 7 h per day for 25 days under T₁ and T₂. A comparative study of growth, membrane permeability, and polyamine content in cucumber leaves under T₁ and T₂ treatments was conducted. UV-B radiation resulted in the dose-dependent decrease in leaf area, dry weight of foliage, and plant height. The T₁ and T₂ treatments caused an increase in the contents of putrescine, spermine, and spermidine. However, the total polyamine content declined slightly when electrolyte leakage increased dramatically on the 18th day of treatment, especially after T₂ treatment. It can be concluded that polyamine accumulation in the cucumber leaves is an adaptive mechanism to the stress caused by UV-B radiation.     

不同盐处理对玉米幼苗根系质子分泌及细胞膜透性的影响

以玉米品种郑单958为实验材料,分别用100 mmol/L NaCl、100 mmol/L KCl和50 mmol/L Na2CO3处理其幼苗3 d,研究不同盐类对玉米根系质子分泌和细胞膜透性的影响.结果表明:不同盐处理都显著抑制玉米幼苗根系的生长,抑制程度依次为Na2CO3>KCl>NaCl;不同盐处理均使玉米幼苗根系Na 含量显著增加,NaCl和Na2CO3处理显著降低根系K 含量而导致其Na /K 升高,但KCl处理却显著提高根系K 含量使其Na /K 降低;不同盐处理均能显著增加细胞膜透性而降低根系质子分泌能力,影响程度依次为Na2CO3>KCl>NaCl.研究发现,相同阳离子浓度条件下,KCl处理对玉米根系质子分泌的抑制作用强于NaCl,碱性盐的抑制作用大于中性盐;盐胁迫可能通过改变玉米幼苗根系质膜的稳定性来影响质子分泌,从而抑制根系生长.     

苏北沿海防护林对土壤渗透性的影响

苏北沿海防护林对土壤渗透性的影响＊仇才楼梁珍海康立新（江苏省沿海防风林试验站,射阳２２４３００）（江苏省林业科学研究所,南京２１１１５３）胡海波徐春（南京林业大学森林资源与环境学院,２１００３７）（江苏省国营射阳林场,２２４３００）Ｉｎｆｌｕｅｎｃｅ...     

家蝇幼虫抗菌肽MDL-2对细菌细胞渗透性及代谢功能影响

研究了家蝇幼虫抗菌肽MDL-2与细菌相互作用时,抗菌肤MDL-2对细菌细胞壁的溶解作用、细胞膜渗透性和代谢的影响.抗菌肽MDL-2在抗菌过程中首先与细菌的细胞壁相互作用,使其破裂,抗菌肽对革兰氏阴性细菌大肠杆菌细胞壁的作用有浓度依赖性,而对革兰氏阳性细菌金黄色葡萄球菌MDL-2在较低的浓度时即可发生细胞壁破坏作用;抗菌...     

Effect of Naturally Occurring Flavonoids on Lipid Peroxidation and Membrane Permeability Transition in Mitochondria

The ability of eight structurally related naturally occurring flavonoids in inhibiting lipid peroxidation and mitochondrial membrane permeability transition (MMPT), as well as respiration and protein sulfhydryl oxidation in rat liver mitochondria, was evaluated. The flavonoids tested exhibited the following order of potency to inhibit ADP/Fe(II)-induced lipid peroxidation, estimated with the thiobarbituric acid assay: 3′-O-methyl-quercetin > quercetin > 3,5,7,3′,4′-penta-O-methyl-quercetin > 3,7,3′,4′-tetra-O-methyl-quercetin > pinobanksin > 7-O-methyl-pinocembrin > pinocembrin > 3-O-acyl-pinobanksin. MMPT was estimated by the extent of mitochondrial swelling induced by 10 μM CaCl₂ plus 1.5 mM inorganic phosphate or 30 μM mefenamic acid. The most potent inhibitors of MMPT were quercetin, 7-O-methyl-pinocembrin, pinocembrin, and 3,5,7,3′,4′-penta-O-methyl-quercetin. The first two inhibited in parallel the oxidation of mitochondrial protein sulfhydryl involved in the MMPT mechanism. The most potent inhibitors of mitochondrial respiration were 7-O-methyl-pinocembrin, quercetin, and 3′-O-methyl-quercetin while the most potent uncouplers were pinocembrin and 3-O-acyl-pinobanksin. In contrast 3,7,3′,4′-tetra-O-methyl-quercetin and 3,5,7,3′,4′-penta-O-methyl-quercetin showed the lowest ability to affect mitochondrial respiration. We conclude that, in general, the flavonoids tested are able to inhibit lipid peroxidation on the mitochondrial membrane and/or MMPT. Multiple methylation of the hydroxyl substitutions, in addition to sustaining good anti-lipoperoxidant activity, reduces the effect of flavonoids on mitochondrial respiration, and therefore, increases the pharmacological potential of these compounds against pathological processes related to oxidative stress.     

Modeling Response of N Addition on C and N Allocation in Scandinavian Norway Spruce Stands

Because nitrogen is considered to be the major growth-limiting element in boreal forests, the increasing nitrogen availability from deposition should lead to increasing growth. We have tested this assumption by simulating, with a simple model, carbon and nitrogen development in seven long-term fertilization experiments in three Nordic countries. The only differences between sites in the model are climate, the ambient nitrogen deposition, nitrogen fertilization regimes, and the initial conditions at the start of the experiment. The model simulates the observed stand development well as long as nitrogen remains the limiting factor. The simulated retention of deposited nitrogen is in general low (less than 50%), whereas retention of fertilizer nitrogen is higher. This seems to imply that the higher production in the fertilized stands will not be maintained once the fertilization is stopped. The model results also indicate that the major effect of climate on site productivity is through soil processes, not tree physiology.     

干旱胁迫对烟草叶片丙二醛含量和细胞膜透性的影响

对干旱胁迫下5个烟草品种(系)丙二醛含量和细胞膜透性进行测定表明,随着干旱胁迫的不断加重,烟草叶片丙二醛含量呈现先升后降的趋势,而细胞膜透性则表现为持续升高;复水后细胞膜透性能很快恢复正常,而丙二醛含量需要较长时间才略有恢复。细胞膜透性反应了烟草受干旱胁迫的程度,而丙二醛含量的稳定对烟草的抗旱性有重要意义。     

Pit membrane remnants in perforation plates of Hydrangeales with comments on pit membrane remnant occurrence, physiological significance and phylogenetic distribution in dicotyledons

Perforation plates from ten species of seven genera of Hydrangeales sensu Thorne were studied using scanning electron microscopy (SEM). The presence of pit membranes in perforations ranges from abundant, as in Carpenteria and Hydrangea, to minimal, as in Deutzia, Escallonia and Philadelphus. Abnormally great pit membrane presence may result from the presence of secondary compounds that inhibit lysis, as in Quintinia serrata; such interference with the natural lysis process may or may not be evident from coarseness and irregularity of pit membrane surface and of threads composing the pit membrane remnants. The presence of pit membrane remnants in perforation plates is hypothesized to be a symplesiomorphy, found in a fraction of dicotyledons with scalariform perforation plates (but still in an appreciable number of species). Pit membrane remnant presence may represent incomplete lysis of primary wall material (cellulose microfibrils) in species that occupy highly mesic habitats, where such impedance in the conductive stream does not have an appreciable negative selective value. This physiological interpretation of pit membrane remnants in perforations is enhanced by the phylogenetic distribution as well as the strongly mesic ecological preferences of species that exemplify this phenomenon in dicotyledons at large. Families with pit membrane presence in perforations are scattered throughout phylogenetic trees, but they occur most often in basal branches of major clades (superorders) or as basal branches of orders within the major clades. Further study will doubtless reveal other families and genera in which this phenomenon occurs, although it is readily detected only with SEM. Phylogenetic stages in the disappearance of pit membrane remnants from perforation plates are described, ranging from intact pit membranes except for presence of pores of various sizes, to presence of membrane remnants only at lateral ends of perforations and in one or two perforations (arguably pits) at the transition between a perforation plate and subadjacent lateral wall pitting. Developmental study of the mechanism and timing of lysis of pit membranes in perforations, and assessment of the role of the conductive stream in their removal, are needed to enhance present understanding of vessel evolution. © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society, 2004, 146 , 41–51.     

小檗碱改善流感病毒性肺炎小鼠肺血管通透性的作用及机制

目的:观察小檗碱对流感病毒感染所致病毒性肺炎小鼠肺血管通透性的影响,并探讨其作用机制。方法:BALB/c小鼠108只随机分为3组,正常组、模型组、小檗碱组,25μL 50LD50病毒液滴鼻建立流感病毒感染的小鼠肺炎模型,感染后1 h,正常组和模型组予以双蒸水灌胃,小檗碱组予药物0.005 g.kg-1d-1腹腔注射;各组均给药2次/d,连续给药5 d。感染后的2 d、4 d、6 d,处死小鼠,肺组织称重以检测肺含水量;1%伊文氏兰5 mL/kg尾静脉注射检测肺血管通透性;Bicinchoninic acid(BCA)法检测肺泡灌洗液(BALF)中蛋白含量;放免法或酶免法测定肺组织中PGE2、PLA2及LT-B4含量。结果:病毒感染后,模型组肺含水量持续升高,肺血管通透性及BALF蛋白含量在感染后第4天开始明显升高,小檗碱降低了肺含水量、肺血管通透性及BALF蛋白含量(P<0.01);模型组肺组织中PGE2、PLA2、LT-B4的含量明显升高,小檗碱不同程度地抑制了PGE2、PLA2、LT-B4的表达。结论:小檗碱通过抑制流感病毒感染后肺组织中PGE2、PLA2、LT-B4的释放,降低了肺血管通透性及肺含水量,对病毒性肺炎中肺水肿的形成,起到一定的治疗作用。     

NaCl胁迫对毛竹叶片的电阻抗图谱参数及膜透性的影响

以NaCl胁迫下毛竹（Phyllostachys edulis）实生苗叶片为材料,测定其电阻抗图谱参数和膜透性的变化,通过膜透性与电阻抗图谱参数间的相关性,来证明电阻抗图谱法研究竹子受胁迫程度的有效性。结果表明：随着盐浓度的升高,胞外电阻、胞内电阻和弛豫时间呈现先减小、后增加、再减小的特征,而弛豫时间分布系数表现恰好相反;叶片细胞膜相对透性逐渐增大,脯氨酸的含量先逐渐增大,然后减小。相关分析表明：胞内电阻、胞外电阻、弛豫时间与脯氨酸含量呈极显著负相关（p〈0.01）;胞外电阻、弛豫时间与膜相对透性呈显著负相关（p〈0.05）。电阻抗图谱参数能够有效地表示毛竹受NaCl胁迫的程度,电阻抗图谱法将是竹子逆境胁迫研究的一种有效方法。