pH值对香蕉枯萎病菌4号生理小种生长的影响

【背景】香蕉枯萎病菌4号生理小种(镰刀菌)是香蕉产业的致命威胁。已有研究表明土壤pH值越高,香蕉枯萎病发病率越低,但是现有pH值对镰刀菌影响的研究大都是用强酸强碱调节pH值,pH值没有缓冲体系保护,而且尚未检测试验终点时介质的pH值。此外,关于pH值对香蕉枯萎病菌4号生理小种(Foc4)影响的研究尚不系统,难以用于指导生产实践。【目的】为系统地了解土壤酸碱度对Foc4生长的影响。【方法】在pH 3.0-11.0之间设定9个pH值梯度,模拟酸性到碱性土壤pH值条件,于室内培养条件下系统研究pH值对Foc4生长、产孢、孢子萌发的影响及其生长过程对环境pH值的影响。【结果】弱酸性至中性环境(pH 5.0-7.0)最适宜于香蕉枯萎病菌的生长、产孢和孢子萌发。弱碱性处理(pH8.0和pH9.0)孢子平均萌发率较弱酸性环境处理(pH5.0和pH6.0)下降了73.1%。与pH 6.0酸性处理相比,pH 8.0和pH 9.0处理的产孢量分别下降了52.3%和68.1%。【结论】香蕉枯萎病菌Foc4生长和萌发过程会产酸,但是在缓冲体系液体培养基中,除了pH 9.0和pH10.0处理终点培养液pH值分别下降了0.34和0.27个单位外,其它处理起始和终点的pH值无差异。说明在缓冲体系液体培养基中的研究结果可以反映环境pH值对Foc4生长和萌发的影响。在作物可以生长的pH值范围内(pH5.0-9.0),碱性和微碱性条件(pH8.0-9.0)能明显抑制Foc4生长、产孢和孢子萌发。     

初始pH值对碱性和酸性水稻土微生物铁还原过程的影响

酸碱度(pH值)是水稻土铁还原过程的重要影响因素之一。通过模拟水稻土淹水厌氧培养,以Al2(SO4)3和Na2CO3溶液分别调节碱性和酸性水稻土pH值至强酸性(pH值5.0)、酸性(pH值5.0—6.5)、中性(pH值6.5—7.5)、碱性(pH值7.5—8.5)、强碱性(pH值8.5),以此来研究5种初始pH值对水稻土泥浆铁还原过程的影响;通过微生物群落厌氧培养研究了2种水稻土菌悬液在6种pH值条件下的铁还原能力差异。结果表明,碱性水稻土铁还原潜势(a)、最大铁还原速率(V max)随初始pH值的降低而下降,而达到最大铁还原速率所需的时间(T Vmax)则延长。提高酸性水稻土初始pH值使铁还原V max增加而T Vmax缩短,但土壤中无定形氧化铁均能还原,初始pH值与V max具有显著正相关关系。碱性和酸性水稻土的土壤菌悬液在试验pH值范围内厌氧培养,其铁还原能力在培养初期差异不显著,但培养后期的差异明显,且最终都能把培养液中氧化铁完全还原。随着初始pH值升高T Vmax延长,V max则降低,且均显著负相关,但碱性水稻土微生物群落的V max在pH值6.00时最大。初始pH值和土壤类型对水稻土铁还原过程具有显著影响,且对土壤菌悬液微生物群的铁还原具有一定影响。     

植物组织培养中与pH值变化有关的一些问题

处理介质和培养介质经过高压灭菌后可能产生短期pH值波动。环境pH值和其他多种因素都能影响胞内pH植。环境pH值可能影响膜状况、跨膜流、激素在胞内作用、呼吸状况、代谢状况、细胞分裂和分化。因此应该重视环境pH值对植物组织培养物的影响,研究pH值对植物组织培养效率的调控规律和调控胞质pH值的可能途径。     

pH值检测器

目前,测定pH值是化学实验室最常用的分析方法。然而,pH值的测定往往会因为选用的物质材料不对或保养方法不当而受到影响,下面介绍一种测定pH值的简便方法:此种pH值的测定系统由4个部分组成:一个pH值自动检测电极;一个放大器,它可以将信号译为可供仪器操作者阅读的符号;一个参考电极;以及需要测定其pH值的样品。用玻璃材料制成的检测电极实际上是一个小电池,它随着浸泡它的溶液pH值的不同而     

不同pH值缓冲液中蚕豆花药小孢子的有丝分裂状况

近年来随着细胞内pH值测定技术的改进,对胞内pH值生理影响的研究报告显著增多。在动物细胞方面,有报告指出细胞在分裂时胞内pH值有明显升高的变化。并有报告指出外源pH值可以通过影响胞内pH值而影响细胞的分裂。在植物细胞,也     

模拟酸雨胁迫对茶树幼苗生长和光合生理的影响

茶是世界三大饮料之一,并且茶树在中国被广泛种植。酸雨是中国乃至全球面临的主要环境问题,本研究选用一年生茶树幼苗作为实验材料,品种为湘妃翠,采用盆栽的方法培养,通过模拟pH值2.5、pH值3.5、pH值4.5酸雨以及自来水(pH值6.5)作为对照对茶树进行全喷淋,探究模拟酸雨对茶树幼苗生长状况和光合生理的影响。结果表明pH值4.5模拟酸雨对茶树幼苗生长有一定促进作用,pH值2.5模拟酸雨对茶树幼苗生长具有抑制作用。茶树幼苗SPAD值(叶绿素相对含量)、以及叶绿素荧光参数Fv/Fm(PSⅡ最大光能转换率)、Fv/Fo(PSⅡ潜在活性)在pH值2.5酸雨胁迫下与对照组相比都显著降低,Fo(初始荧光产量)则显著增大。由此说明pH值2.5模拟酸雨对茶树幼苗具有较强的胁迫作用,pH值4.5模拟酸雨对茶树幼苗生长有促进作用。     

影响白腐真菌J610-D对染料苋菜红脱色降解的培养因素

建立白腐真菌J610-D与苋菜红的共培养体系,研究培养参数对染料脱色降解的影响。结果表明：（1）在含缓冲成分的系统中,菌种J610-D在pH值4．5的培养液比pH值3．0有利于反应进行,浅层培养较深层培养好,缓冲成分差别的作用不明显。（2）在不舍缓冲成分的系统中,生长与反应阶段培养液均为pH值4．5时,效果最佳;生长于pH值4．5,反应在pH值3．0脱色率和降解率高于生长及反应都在pH值3．0的情况,但仍有25％～40％的苋菜红牢固地结合在菌体上;pH值4．5生长,pH值6．0反应,导致反应启动滞后约4～6d,最终结果尚好。     

花生磷脂酶D的pH值记忆效应

研究了花生磷脂酶D（PLD）的pH值记忆效应,结果表明,花生PLD在冻干过程中具有pH值记忆效应。冻干PLD分散于有机溶剂中对pH值记忆效应的保持与溶剂种类有关。在所研究的有机溶剂范围内,冻干PLD分散于氯仿、二氯甲烷、乙醚、甲苯和正己烷中仍然能保持这种pH值记忆效应。但在苯中PLD氨基pKa变化较大,增加了0．738,说明PLD在苯中保持pH值记忆效应的能力较差。     

G_3基因工程菌发酵中pH值对包涵体形成及目的蛋白表达的影响

在不同pH值条件下摇瓶及罐发酵G3双体分子重组菌．探讨pH值对G3双体分子包涵体形成及目的蛋白表达水平的影响,确定G3双体分子重组菌发酵最佳pH值为生长期pH7．0—7．2,生产期pH6．7－6．8．     

植物抗污机理的研究 Ⅰ.叶细胞的pH值、等电点、缓冲容量与抗二氧化硫的关系

前言关于植物对污染物的抗性机理,细胞pH值高的植物,抗性强,pH值低的植物,抗性弱,但其中也有一些相反的情况。枞树针叶的抗性与它的缓冲容量有关。本研究的目的,在于探讨pH值及与pH值有关的几项生理性状——pH值、等电点、缓冲容量与植物抗二氧化硫的关系。     

Use of high culture pH for the decreased proteolysis of human parathyroid hormone secreted by Saccharomyces cerevisiae

Human parathyroid hormone (hPTH) was expressed and secreted in Saccharomyces cerevisiae. In batch fermentations performed at pH = 5.6, 6.5, 7.2 and 7.5, optimal production of hPTH (12.1 mg/l) was obtained at pH 7.2 after 24 h of culture. At pH 5.6, most of secreted hPTH was degraded. Proteolysis of hPTH was significantly decreased by increasing the culture pH.     

模拟酸雨胁迫对青冈幼苗光合特性和叶绿素荧光参数的影响

选择亚热带常绿阔叶林优势树种青冈幼苗为研究对象,设置3个酸雨处理：pH 2.5、pH 4.0、pH 5.6(CK),研究不同强度的模拟酸雨对青冈幼苗光合特性、叶绿素荧光参数和叶绿素含量的影响.结果表明：经过2年酸雨处理,青冈的净光合速率随着酸雨强度的增加而显著上升.pH 2.5、pH 4.0处理的酸雨增大了青冈的气孔导度和蒸腾速率,且对pH 2.5处理的影响更为显著.胞间CO₂浓度的大小顺序是pH 2.5>pH 5.6>pH 4.0.pH 2.5、pH 4.0处理青冈的最大净光合速率、光补偿点、光饱和点、暗呼吸速率显著高于对照,表观量子效率对酸雨胁迫不敏感.pH 2.5、pH 4.0处理青冈的PSⅡ原初光能转化效率和PSⅡ的潜在活性显著高于对照.青冈的叶绿素相对含量大小顺序是pH 2.5>pH 5.6>pH 4.0,且pH 2.5与pH 4.0之间有显著差异.说明青冈幼苗的光合参数、叶绿素荧光参数指标在pH 2.5和pH 4.0的酸雨处理下有所增加,且在pH 2.5强度下增加更为明显.     

Estrogen-induced changes in the maltase activity of rat uterus

The effect of estrogen administration on uterine maltase activities at pH 4.3, 5.6 and 6.2 have been studied in the ovarleotomized immature rat. Estradiol (in total doses of 0.5, 1.0 and 2.0 /ug) for 3 consecutive days resulted in increased uterine maltase levels at pH 4.3 and pH 5.6, though the activity at pH 6.3 remained unchanged. A single injection of 2/ug estradiol resulted in an increase in the enzyme activities at pH 4.3 and pH 5.6; this was detectable in 36 hours and reached peak levels 48 hours after the hormone injection. Actinomycin and cycloheximide blocked the estradiol-induced increase in the enzyme activities. Pretreatment with clomiphene also neutralized estradiol-induced increases in the enzyme activities.     

The host plant-mediated impact of simulated acid rain on the development and reproduction of Tetranychus cinnabarinus (Acari, Tetranychidae)

Abstract:  The host plant-mediated impact of simulated acid rain (pH 3.0, 3.5, 4.0, 5.6, and 6.8) on the behaviour, development, and reproduction of carmine spider mite, Tetranychus cinnabarinus (Boisduvals), were evaluated at 25°C in a series of laboratory trials. The results indicated that the adults of carmine spider mite prefer to aggregate on pH 4.0 acid rain-treated eggplant leaves. The developmental times of nymph, larva and the pre-oviposition period of the mite on kidney bean leaves were significantly affected by acid rain treatments. The developmental times for the immature stages ranged from 11.4 days on pH 4.0 acid rain-treated leaves to 12.7 days on other acid rain-treated leaves. The survival of immatures varied from 85.14% on pH 4.0 acid rain-treated leaves to 78.83% on deionized water-treated leaves (pH 6.8). The mites feeding on acid rain-treated leaves (pH 3.0–5.6) had significantly greater reproductivity and longevity than those feeding on deionized water-treated leaves. The average greatest reproductivity (74.6 eggs per female) and longest female longevity (8.9 days) were recorded on pH 4.0 acid rain-treated leaves. Accordingly, the intrinsic rate of increase ( r _m ) for the mite on pH 4.0 acid rain-treated leaves was the highest. Jackknife estimates of r _m varied from 0.201 on pH 4.0 acid rain-treated leaves to 0.158 on pH 5.6 acid rain-treated leaves. The results implied that the population growth of the mite were enhanced by application of acid rain (pH 3.0–5.6) on host plants.     

Sorption of zinc and lead on coir

Pilot tests have shown that coir (fibres from Coco nucifera) is suitable as a metal ion sorbent. Batch sorption experiments were carried out with Zn and Pb to quantify the sorption kinetics, the pH dependence of the sorption, sorption isotherms at pH 3.0 and pH 5.6, and desorption. Unground and unmodified coir was used and the metal concentrations ranged between 0 and 0.015 mM (1000 microg/l) for Zn and 0 and 9.7 x 10(-4) M (200 microg/l) for Pb. The pH maximum was 4.5 (91%) for Zn and 2.5 (97%) for Pb. Pb had a higher sorption affinity than Zn, and the affinity was higher at pH 5.6 than at pH 3.0. The isotherms could be represented by the Freundlich, but not by the Langmuir models in the concentration range tested. Desorption experiments demonstrated that less than 1% and 13% of the sorbed Pb and Zn, respectively, could be desorbed at pH 5.6 during 2h.     

Production of a homogeneous Cl. botulinum type B neurotoxin

The method for obtaining the neurotoxin, or alpha-fraction of the toxin, of Cl. botulinum, type B, is described. In accordance with this method, the toxin was precipitated three times with hydrochloric acid in the isoelectric zone with subsequent extraction with phosphate (pH 6.8) and citrate-phosphate (pH 5.6) buffers, then fractionated in columns with DEAE cellulose (pH 5.6), DEAE Sephadex A-50 (pH 7.2) and Sephadex G-200 (pH 7.2). The homogeneous neurotoxin preparations with molecular weights ranging from 145,000 to 160,000 and having the isoelectric point at pH 5.5 and toxicity 5.0--10.0 x 10(7) Dlm per 1 mg protein were obtained.     

不同pH值对樱草原生质体分离的影响

用国产纤维素酶分离四季樱草叶肉细胞原生质体,分别在八种pH值(5.2,5.4,5.6,5.8,6.0,6.2,6.4和6.6)下进行酶处理试验,得出5.6是最佳pH值的结果。     

Binding of L-selectin to its vascular and extravascular ligands is differentially regulated by pH

Ligands for L-selectin, a leukocyte adhesion molecule, are expressed in high endothelial venules (HEVs) in lymph nodes and extravascular tissues, such as renal tubules. Here, we report that the binding of L-selectin to its vascular and extravascular ligands is differentially regulated by pH. The optimal L-selectin-dependent binding of leukocytes to HEVs was observed at pH 7.4, a physiological pH in the blood. In contrast, the optimal binding of leukocytes to the renal tubules was observed at pH 5.6. Consistently, optimal binding of soluble recombinant L-selectin to a major vascular ligand, 6-sulfo sialyl Lewis X, was observed at pH 7.4. Binding to extravascular ligands, such as chondroitin sulfate (CS) B, CS E and heparan sulfate, occurred at pH 5.6. Under physiological shear stress ranging from 1 to 2 dynes/cm², maximal leukocyte rolling on vascular ligands was observed at pH 6.8 to 7.4, and no rolling was detected at pH conditions below 5.6. These findings suggest that the pH environment is one important factor that determines leukocyte trafficking under physiological and pathological conditions.     

Cluster-root formation, carboxylate exudation and proton release of Lupinus pilosus Murr. as affected by medium pH and P deficiency

The study examined the interactive effect of pH and P supply on cluster-root formation, carboxylate exudation and proton release by an alkaline-tolerant lupin species (Lupinus pilosus Murr.) in nutrient solution. The plants were exposed to 1 (P₁, deficient) and 50 μM P (P₅₀, adequate) for 34 days in nutrient solution at either pH 5.6 or 7.8. Plant biomass was not influenced by pH at P₁, but at P₅₀ shoot and root dry weights were 23 and 18% higher, respectively, at pH 7.8 than at pH 5.6. There was no significant difference in plant biomass between two P treatments regardless of medium pH. Phosphorus deficiency increased significantly the number of the second-order lateral roots compared with the P₅₀ treatment. Both total root length and specific root length of plants grown at pH 5.6 were higher than those at pH 7.8 regardless of P supply. Cluster roots were formed at P₁, but cluster-root number was 2-fold higher at pH 7.8 than pH 5.6. Roots released 16 and 31% more protons at pH 5.6 and 7.8, respectively, in P₁ than in P₅₀ treatments, and the rate of proton release followed the similar pattern. At pH 5.6, citrate exudation rate was 0.39 μmol g⁻¹ root DW h⁻¹ at P₁, but was under the detection limit at P₅₀; at pH 7.8, it was 2.4-fold higher in P₁ than in P₅₀ plants. High pH significantly increased citrate exudation rate in comparison to pH 5.6. The uptake of anions P and S was inhibited at P₁ and high pH increased cations Na, Mg and Ca uptake. The results suggested that enhanced cluster-root formation, proton release and citrate exudation may account for the mechanism of efficient P acquisition by alkaline-tolerant L. pilosus well adapted to calcareous soils. Cluster-root formation and citrate exudation in L. pilosus can be altered by medium pH and P deficiency. Phosphorus deficiency-induced proton release may be associated with the reduced anion uptake, but high pH-induced proton release may be partly attributed to increased cation uptake.     

L-ascorbic acid 2-sulphate. A substrate for mammalian arylsulphatases.

Ascorbic acid 2-sulphate has a stability in acid comparable to that of phenyl sulphate and is rather more acid-labile than simple carbohydrate sulphates. At its optimum pH of 4.8 sulphatase A(aryl-sulphate sulphohydrolase EC 3.1.6.1.) hydrolyses ascorbic acid sulphate with a specific activity of 90 mumol/mg per min (150 mumol/mg per min with nitrocatechol sulphate at pH 5.6). At pH 4.8 the kinetics are non-Michaelis. At pH 5.6 Michaelis kinetics are obeyed and Km 12 21 mM ascorbic acid 2-sulphate. K2SO4 is a competitive inhibitor with a Ki of 0.2 and 0.6 mM at pH 4.8 and 5.6, respectively. Sulphatase A is converted into a substrate-modified form during its hydrolysis of ascorbic acid sulphate. Sulphatase B also hydrolyses ascorbic acid 2-sulphate. At pH 4.8 and in the presence of 0.15 M NaCl the specific activity is 0.92 mumol/mg per min (90 mumol/mg per min for nitrocatechol sulphate at pH 5.6). In the absence of NaCl the activity is greatly decreased. Km is 8 mM. K2SO4 is a competitive inhibitor with a Ki of 0.1 mM. Ascorbic acid is not hydrolysed at a detectable rate by the arylsulphatases of the mollusc Dicathais orbita or of Aerobacter aerogenes.?