不同钙离子浓度对喜钙和嫌钙型金花茶光合及生理指标的影响

为探讨喜钙型金花茶对高钙环境的生理适应机制以及嫌钙型金花茶的避钙机理,该文采用砂培法,分别以两种喜钙型金花茶[直脉金花茶(Camellia multipetala)、柠檬金花茶(C.limonia)]和两种嫌钙型金花茶[金花茶(C.nitidissima)、东兴金花茶(C.tunghinensis)]的幼苗为材料,用不同浓度(设为5、25、50、100 mmol·L-1)的钙离子(Ca²⁺)营养液进行培养,研究其对两种不同类型金花茶的光合及生理指标的影响。结果表明:两种嫌钙型金花茶的净光合速率(P n)、气孔导度(G s)、实际光化学效率(ΦPSⅡ)、电子传递效率(ETR)、叶绿素a(Chl a)、叶绿素b(Chl b)、叶绿素总量[(Chl(a+b)]均随Ca²⁺浓度的升高而降低,表明高钙环境降低了嫌钙型金花茶的光合能力;喜钙型金花茶的这些指标在不同Ca²⁺浓度下无显著变化,高钙环境未影响其光合作用的正常进行。嫌钙型金花茶叶片丙二醛含量和PSⅡ最大光化学效率(F v/F m)在高钙环境下未有显著变化,表明其光合膜系统还未受到伤害。随着Ca²⁺浓度的升高,嫌钙型金花茶叶片脯氨酸含量显著增加,而可溶性糖含量变化却不大;喜钙型金花茶在不同Ca²⁺浓度下脯氨酸和可溶性糖含量的变化均不明显,但其可溶性糖含量却明显高于嫌钙型金花茶。喜钙型金花茶对外界钙离子浓度的变化不敏感,其适应高钙的生理机制可能与叶片较高的可溶性糖含量有关;而嫌钙型金花茶对高钙环境的适应性较差,这可能是其不能在钙质土上生长的主要原因。     

介质中不同Ca~(2+)浓度对五种榕树幼苗钙含量的影响

选择高榕(Ficusaltissima)、木瓜榕(F.auriculata)、聚果榕(F.racemosa)、鸡嗉子榕(F.semicorda ta)以及对叶榕(F.hispida)5种榕树,对其幼苗进行不同Ca2+(CaCl2)浓度下的水培实验,结果表明,5种幼苗钙含量随介质Ca2+浓度的增加而增加,增加趋势大致相同。高Ca2+浓度下(10mmol/L)幼苗地上部的钙含量为低Ca2+浓度下(0.05mmol/L)的1.51～1.63倍。5种榕树幼苗钙含量随培养液Ca2+浓度变化的Yadj值的多重比较结果显示,对叶榕钙含量显著高于其他四种(P<0 01),高榕则显著低于其他四种(P<0 01),木瓜榕、聚果榕、鸡嗉子榕之间的差异不显著。不同榕树幼苗地上部分钙含量受介质钙浓度影响,但可能主要决定于基因型的差异,表明榕属植物富钙基因的存在,这为高钙榕树植物资源开发提供初步的理论依据。     

不同钙浓度对宽叶雀稗幼苗的生长和抗性生理的影响

研究不同钙浓度对宽叶雀稗(Paspalum wettsteinii)幼苗生长和生理的影响, 对于揭示宽叶雀稗对不同钙浓度环境的适应机理至关重要。该研究采用盆栽砂培试验, 研究不同钙浓度(0、5、25、50、100和200 mmol·L^-1 CaCl₂)和不同处理时间(7、14、21和28天)对宽叶雀稗幼苗生长、渗透调节物质含量、抗氧化酶活性、叶绿素含量和光合参数的影响。结果表明, 随着CaCl₂浓度的增加和处理时间的延长, 宽叶雀稗幼苗株高等形态指标、生物量、渗透调节物质含量、抗氧化酶活性、叶绿素含量和光合参数呈先增后减的趋势, 低钙浓度(5-50 mmol·L^-1)环境下, 株高、叶长、叶宽、根长和生物量与对照(0 mmol·L^-1)相比均升高, 脯氨酸、可溶性蛋白和可溶性糖含量、过氧化物酶、过氧化氢酶和超氧化物歧化酶活性提高, 丙二醛含量和胞间CO₂浓度降低、叶绿素含量增加以及净光合速率、蒸腾速率和气孔导度增强; 高钙浓度(200 mmol·L^-1)环境下, 脯氨酸、可溶性蛋白和可溶性糖含量、过氧化物酶、过氧化氢酶和超氧化物歧化酶活性降低, 丙二醛含量和胞间CO₂浓度增加, 叶绿素含量减少以及净光合速率、蒸腾速率和气孔导度减弱。结合隶属函数分析, 低钙盐浓度(5-50 mmol·L^-1)处理对宽叶雀稗幼苗无抑制作用, 说明宽叶雀稗对低钙浓度具有一定的耐受性; 而在高钙浓度(200 mmol·L^-1)下, 宽叶雀稗幼苗通过提高自身有机渗透调节物质含量、增强酶活性、增加叶绿素含量以及增强光合作用等方式来快速调节植物生理代谢功能, 进而适应高钙浓度环境条件。     

外源钙离子对南方菟丝子寄生入侵植物喜旱莲子草效果的影响

外源钙离子可以有效地缓解植物在胁迫下受到的毒害,提高植物组织或细胞抗胁迫的能力。以喜旱莲子草为研究对象,采用完全随机区组的实验设计,研究不同钙离子浓度与南方菟丝子寄生对喜旱莲子草茎生物量的影响,探讨外源钙离子是否可以减少南方菟丝子对喜旱莲子草的损伤。研究表明南方菟丝子寄生对喜旱莲子草的根、茎和叶的生物量具有显著影响,且南方菟丝子寄生与外源钙离子对喜旱莲子草茎和叶的生长具有显著的交互作用。不同浓度的钙离子与南方菟丝子寄生对喜旱莲子草茎生物量存在拮抗的交互作用;而仅8 mmol/L Ca2+与南方菟丝子寄生对喜旱莲子草叶生物量存在拮抗的交互作用。不同浓度钙离子均可以缓减南方菟丝子对喜旱莲子草茎的有害效应,仅8 mmol/L Ca2+可以缓减南方菟丝子对喜旱莲子草根和叶的有害效应。2—6 mmol/L的外源钙离子对南方菟丝子寄生下的喜旱莲子草的丙二醛(MDA)含量无显著影响,但可以显著地降低过氧化物酶(POD)活性,表明低浓度的外源钙离子的添加可以缓减南方菟丝子对喜旱莲子草的寄生胁迫,并体现在生理指标上。     

不同钙浓度对宽叶雀稗幼苗的生长和抗性生理的影响

研究不同钙浓度对宽叶雀稗(Paspalum wettsteinii)幼苗生长和生理的影响,对于揭示宽叶雀稗对不同钙浓度环境的适应机理至关重要。该研究采用盆栽砂培试验,研究不同钙浓度(0、5、25、50、100和200 mmol·L~(–1) Ca Cl_2)和不同处理时间(7、14、21和28天)对宽叶雀稗幼苗生长、渗透调节物质含量、抗氧化酶活性、叶绿素含量和光合参数的影响。结果表明,随着Ca Cl_2浓度的增加和处理时间的延长,宽叶雀稗幼苗株高等形态指标、生物量、渗透调节物质含量、抗氧化酶活性、叶绿素含量和光合参数呈先增后减的趋势,低钙浓度(5–50 mmol·L~(–1))环境下,株高、叶长、叶宽、根长和生物量与对照(0 mmol·L~(–1))相比均升高,脯氨酸、可溶性蛋白和可溶性糖含量、过氧化物酶、过氧化氢酶和超氧化物歧化酶活性提高,丙二醛含量和胞间CO_2浓度降低、叶绿素含量增加以及净光合速率、蒸腾速率和气孔导度增强;高钙浓度(200 mmol·L~(–1))环境下,脯氨酸、可溶性蛋白和可溶性糖含量、过氧化物酶、过氧化氢酶和超氧化物歧化酶活性降低,丙二醛含量和胞间CO_2浓度增加,叶绿素含量减少以及净光合速率、蒸腾速率和气孔导度减弱。结合隶属函数分析,低钙盐浓度(5–50 mmol·L~(–1))处理对宽叶雀稗幼苗无抑制作用,说明宽叶雀稗对低钙浓度具有一定的耐受性;而在高钙浓度(200 mmol·L~(–1))下,宽叶雀稗幼苗通过提高自身有机渗透调节物质含量、增强酶活性、增加叶绿素含量以及增强光合作用等方式来快速调节植物生理代谢功能,进而适应高钙浓度环境条件。     

盐胁迫下外源Ca2+对花生生长发育、生理及产量的影响

以‘花育22’为试验材料,使用外源钙[0、6、12 mmol·L^-1的Ca(NO₃)₂]处理盐胁迫(100 mmol·L^-1 NaCl)及正常条件下生长的花生,以盆栽方式研究了不同Ca²⁺浓度处理对盐胁迫条件下花生整个生育期的相关生理与产量指标的影响.结果表明: 在100 mmol·L^-1 NaCl条件下,施加不同浓度外源钙均可提高超氧化物歧化酶(SOD)、过氧化氢酶(CAT)活性以及叶绿素含量,降低丙二醛(MDA)含量和电解质外渗,增加根系活力,改善植株的农艺性状,增加生物积累量,最终提高花生产量,并且12 mmol·L^-1 Ca²⁺处理的效果最显著.通过增强活性氧的清除能力、维持细胞膜的稳定性以及完整性,是外源钙有效缓解花生植株的盐胁迫伤害并最终提高荚果产量的重要原因.     

植物钙吸收、转运及代谢的生理和分子机制

钙是植物必需的营养元素。酸性砂质土壤中含钙较少, 导致在其土壤上生长的作物容易缺钙。另外由于果树果实、果菜类和包心叶菜类的蒸腾作用弱, 导致果树和蔬菜普遍生理缺钙。根系维管束组织可能通过共质体和质外体两种途径进行钙素吸收, 而果实则可通过非维管束组织直接吸收钙素。Ca2+通过Ca2+通道内流进入胞质, 并通过Ca2+-ATPase 和Ca2+/H+反向转运蛋白外流以保持胞质内低Ca2+浓度。为了应对植物发育和环境胁迫信号, Ca2+由质膜、液泡膜和内质网膜的Ca2+通道内流进入胞质, 导致胞质Ca2+浓度迅速增加, 产生钙瞬变和钙振荡, 传递到钙信号靶蛋白, 如钙调素、钙依赖型蛋白激酶及钙调磷酸酶B类蛋白, 引起特异的生理生化反应。本文综述了植物钙素吸收、转运以及代谢研究的最新进展, 包括植物对钙的需求和作物缺钙的原因, 根系维管束组织及果实钙素吸收机理, Ca2+跨膜运输特性, 钙的信使作用以及钙信号靶蛋白等方面内容。     

外源钙对镉胁迫下南美蟛蜞菊毛状根生长、抗氧化酶活性和镉吸收的缓解效应

为了探讨外源钙对重金属镉(Cd)缓解南美蟛蜞菊Wedelia trilobata毛状根毒害的生理机理,采用溶液培养法研究了重金属Cd单独及其与Ca组合对南美蟛蜞菊毛状根生长、抗氧化酶超氧化物岐化酶(SOD)和过氧化物酶(POD)活性及对Cd2+吸收的影响。结果表明,Cd≤50μmol/L时促进毛状根生长;高于100μmol/LCd则抑制其生长,使其侧根短小,根尖变褐或变黑。与对照相比,不同浓度Cd培养的毛状根POD活性、SOD活性和MDA含量都比对照明显提高,但高于100μmol/L Cd培养的毛状根可溶性蛋白含量均比对照降低。与仅添加200μmol/L或300μmol/L Cd的毛状根相比,Cd和10~30 mmol/L Ca组合培养可促进毛状根生长,使其主、侧根变粗;提高其可溶性蛋白含量;降低其MDA含量、POD活性及SOD活性。原子吸收分光光度法测定结果表明,南美蟛蜞菊毛状根能吸收和吸附重金属Cd2+,当Cd2+浓度为100μmol/L时毛状根对Cd2+的吸收量最大,而Cd2+浓度为300μmol/L时毛状根对Cd2+的吸附量最大。外源加入10~30 mmol/L Ca2+可显著减少毛状根对Cd2+的吸收和吸附,并可调节其抗氧化酶活性,降低其膜脂过氧化水平而解除重金属镉对毛状根生长的抑制或毒害。     

不同浓度硝态氮供应下小麦生长、硝态氮累积及根系钙信号特征

以小麦品种‘石麦15’和‘衡观35’为材料进行营养液水培试验,研究不同浓度硝态氮供应对小麦苗期根系形态、钙离子流特征及钙调蛋白(CaM)含量的影响。结果表明,与适宜浓度硝态氮处理(2.5mmol/L)相比,无外源硝态氮供应时小麦地上部鲜重、硝态氮含量均降低,侧根数量显著减少;高浓度硝态氮处理(50mmol/L)下两个小麦品种地上部硝态氮含量升高,根系总长度降低,‘石麦15’侧根数量减少。无硝态氮和高浓度硝态氮处理下,根系中钙调蛋白含量降低,且‘衡观35’的降低幅度大于‘石麦15’。无外源硝态氮供应时小麦根尖表现出较为明显的钙离子外流特征;与适宜浓度硝态氮处理相比,高硝态氮处理下小麦根尖Ca2+的内流速度显著下降。说明硝态氮供应不足和高浓度硝态氮供应会影响小麦根系生长,根系Ca2+外流或Ca2+内流速度下降,CaM含量减少,Ca2+/CaM可能介导硝态氮调控小麦根系生长发育。     

喀斯特地区野生毛葡萄的钙组分特征及其对高钙环境的适应性分析北大核心CSCD

为了探究喀斯特地区野生毛葡萄(Vitis quinquangularis Rehd.)器官的钙含量、组分及其分布特征,揭示野生毛葡萄的需钙特性及其对高钙土壤的适应机制。该研究以贵州喀斯特地区野生毛葡萄为材料,取样测定了40个样地的野生毛葡萄立地土壤的pH值、交换性钙含量及其根、茎、叶中钙和镁及其钙组分含量,分析土壤交换性钙含量与不同钙组分间的关系,并观察野生毛葡萄叶片表面及根、茎、叶中的钙晶体。结果表明:(1)喀斯特地区野生毛葡萄总钙含量在器官中的分布表现为叶>根>茎,其分布特征与喜钙植物类似。(2)野生毛葡萄根、茎、叶中主要钙组分含量由高到低依次基本为草酸钙、果胶酸钙、水溶性钙、磷酸钙+碳酸钙、硝酸钙+氯化钙、硅酸钙(茎中稍有不同),根、茎、叶中草酸钙占所有钙组分总量和总钙含量的比例均最高,其次是果胶酸钙。(3)各样地野生毛葡萄叶片中Ca+Mg的含量范围在1.30%~4.07%之间,绝大多数在3.0%~4.0%范围内,表现出喜钙植物叶中高Ca+Mg含量的特性。(4)在喀斯特地区的野生毛葡萄体内,多种钙组分含量与土壤中的钙含量呈显著或极显著的正相关关系。(5)扫描电镜观察发现,野生毛葡萄叶片和根中储存有大量的草酸钙晶体,叶片中的草酸钙可通过气孔排出体外。研究发现,喀斯特地区野生毛葡萄属于喜钙植物,对喀斯特高钙环境的适应性强,叶片中钙的富集量大,有大量的草酸钙和果胶酸钙储存于体内,这种储钙特性和气孔的排钙行为对野生毛葡萄适应高钙环境具有重要作用。     

Effects of Ca2+ and other divalent cations on K+-evoked force production of slow muscle fibers from Rana esculenta and Rana pipiens

Summary Slow muscle fibers were dissected from cruralis muscles of Rana esculenta and Rana pipiens. Isometric contractures were evoked by application of K⁺-rich Ringer's containing Ca²⁺, Ni²⁺, Co²⁺, Mn²⁺ or Mg²⁺. High (7.2 mmol/liter) external Ca²⁺ concentration raised, 0 Ca²⁺ lowered the K⁺ threshold. Replacing Ca²⁺ by Ni²⁺ or Co²⁺ had an effect similar to that of high Ca²⁺ Ringer's. In Mg²⁺ Ringer's the K⁺ concentration-response curve was flattened. These effects were observed already after short exposure times in both species of slow fibers. When Ca²⁺ was removed for long periods of time the slow fibers of R. esculenta lost their contractile response to application of high K⁺ concentrations much more quickly than those of R. pipiens, while the response to caffeine (20 mmol/liter) was maintained. Upon readmission of Ca²⁺ contractile ability was quickly restored in the slow fibers of both R. esculenta and R. pipiens, but the effects of Ni²⁺ (or Co²⁺, Mn²⁺ and Mg²⁺) were much larger in R. esculenta than in R. pipiens slow fibers. It is concluded that divalent cations have two different sites of action in slow muscle fibers. K⁺ threshold seems to be affected through binding to sites at the membrane surface; these sites bind Ni²⁺ and Co²⁺ more firmly than Ca²⁺. The second site is presumably the voltage sensor in the transverse tubular membrane, which controls force production, and where Ca²⁺ is the most effective species of the divalent cations examined.We are grateful to Mrs. S. Pelvay for technical assistance.     

锰胁迫对盐肤木种子萌发、幼苗生长及理化特性的影响

为揭示植物适应锰胁迫的生理机制,通过在不同Mn²⁺浓度(0、1、5、10、15、20 mmol/L)下开展盐肤木(Rhus chinensis)种子萌发以及幼苗生长实验,检测锰胁迫处理7、15、30 d后幼苗生理生化特性的变化。结果表明:(1)随着Mn²⁺浓度的升高,盐肤木种子发芽率变化不显著,在80.0%-81.6%之间,发芽势、发芽指数和活力指数则呈先升后降的趋势;其幼苗生物量也呈现先升后降的趋势;(2)随着Mn²⁺浓度的升高与胁迫时间的延长,盐肤木幼苗叶绿素a、叶绿素b含量均呈现先增加后降低的趋势,类胡萝卜素含量呈现下降的趋势;(3)胁迫7 d时,随着Mn²⁺浓度的升高,盐肤木幼苗超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性均显著上升;胁迫15、30 d时,高Mn²⁺浓度(15-20 mmol/L)下POD、CAT活性则均降低;(4)胁迫7 d时,随着Mn²⁺浓度的升高,可溶性糖、可溶性蛋白、游离脯氨酸含量升高;胁迫15、30 d时,在Mn²⁺浓度为20 mmol/L时可溶性蛋白与游离脯氨酸含量显著降低;(5)随着Mn²⁺浓度的升高与胁迫时间的延长,丙二醛(MDA)含量均升高。研究说明盐肤木具有较强的耐受锰胁迫能力,它可通过增强抗氧化酶活性、积累渗透调节物质含量来应对锰胁迫。     

Exogenous proline effects on water relations and ions contents in leaves and roots of young olive

The ability of exogenous compatible solutes, such as proline, to counteract salt inhibitory effects was investigated in 2-year-old olive trees (Olea europaea L. cv. Chemlali) subjected to different saline water irrigation levels supplied or not with exogenous proline. Leaf water relations [relative water content (RWC), water potential], photosynthetic activity, leaf chlorophyll content, and starch contents were measured in young and old leaves. Salt ions (Na⁺, K⁺, and Ca²⁺), proline and soluble sugars contents were determined in leaf and root tissues. Supplementary proline significantly mitigated the adverse effects of salinity via the improvement of photosynthetic activity (Pn), RWC, chlorophyll and carotenoid, and starch contents. Pn of young leaves in the presence of 25 mM proline was at 1.18 and 1.38 times higher than the values recorded under moderate (SS1) and high salinity (SS2) treatments, respectively. Further, the proline supply seems to have a more important relaxing effect on the photosynthetic chain in young than in old leaves of salt-stressed olive plants. The differential pattern of proline content between young and old leaves suggests that there would be a difference between these tissues in distinguishing between the proline taken from the growing media and that produced as a result of salinity stress. Besides, the large reduction in Na⁺ accumulation in leaves and roots in the presence of proline could be due to its interference in osmotic adjustment process and/or its dilution by proline supply. Moreover, the lower accumulation of Na⁺ in proline-treated plants, compared to their corresponding salinity treatment, displayed the improved effect of proline on the ability of roots to exclude the salt ions from the xylem sap flowing to the shoot, and thus better growth rates.     

2种鼠尾草对NaCl胁迫的耐受性比较及其生理机制研究

以具有较高药用和观赏价值的美丽鼠尾草和贵州鼠尾草为实验材料,分析2种鼠尾草在NaCl(0、200、300、400、500、600mmol·L-1)胁迫下的生长、叶绿素含量、保护酶活性和有机渗透调节物质含量的变化,以明确2种鼠尾草对NaCl胁迫的耐受性差异及其生理机制。结果显示:(1)在实验NaCl浓度范围内,美丽鼠尾草的受害程度均高于贵州鼠尾草;(2)随着NaCl浓度的提高,贵州鼠尾草叶片叶绿素含量无显著变化,而美丽鼠尾草叶绿素含量逐渐显著降低;(3)当NaCl浓度从0增加到500mmol·L-1时,2种鼠尾草叶片的POD、CAT活性以及可溶性糖、可溶性蛋白质和脯氨酸含量逐渐升高,且美丽鼠尾草叶片的SOD活性也逐渐升高;(4)当NaCl浓度达到600mmol·L-1时,美丽鼠尾草叶片可溶性糖、可溶性蛋白质和脯氨酸含量继续增加,SOD、POD和CAT活性开始降低但仍显著高于对照,而贵州鼠尾草叶片的POD和CAT活性继续增加,可溶性糖、可溶性蛋白质和脯氨酸含量开始降低但仍显著高于对照。研究表明,贵州鼠尾草在NaCl胁迫下具有较高的渗透调节物质含量,而且随着NaCl浓度的增加能够维持较高的保护酶活性,因此对NaCl胁迫的耐受性强于美丽鼠尾草。     

Role of calcium and calmodulin antagonist in photosynthesis and salinity tolerance inChlorella vulgaris

To cast light upon the role of Ca¹⁺ and calmodulin on photosynthetic rate (P_n), dark respiration (R_D) and amino acid and protein contents in salinity stressed and non-stressedChlorella cultures, the Ca²⁺ chelator EGTA [ethylene glycol-bis-(2-aminoethyl ether)-N,N- tetraacetate] and the calmodulin antagonist TFP (trifluperazine) were used. TFP markedly inhibited P_N while EGTA exerted a slight, if any, effect on P_N. NaCl tolerance, on the other side, was markedly abolished by TFP that inhibited P_N and lowered rate of proline accumulation. Calmodulin might be involved in osmoregulation and salt tolerance ofChlorella. R_D, however, was markedly enhanced by EGTA and Ca²⁺-free medium and hence the Ca²⁺ deprivation increased stress severity exerted by NaCl. Combinations of Na⁺ and Ca²⁺ enhanced P_N, decreased R_D and proline content in comparison with an osmotically equivalent reference culture containing only NaCl. Addition of Ca²⁺ to TFP treated cultures failed to reactivate calmodulin for proline synthesis. However, when Ca²⁺ was added to EGTA-treated cultures, only relatively reduced proline contents were recorded.     

Role of protein kinase C in the regulation of cytosolic Ca2+ in A431 cells: Separation of growth factor and bradykinin pathways

Summary Calcium signaling systems in nonexcitable cells involve activation of Ca²⁺ entry across the plasma membrane and release from intracellular stores as well as activation of Ca²⁺ pumps and inhibition of passive Ca²⁺ pathways to ensure exact regulation of free cytosolic Ca²⁺ concentration ([Ca²⁺] _i ). A431 cells loaded with fura-2 cells were used as a model system to examine regulation of Ca²⁺ entry and intracellular release. Epidermal growth factor (EGF) and transforming growth factor alpha (TGF-) both stimulated Ca²⁺ entry and release while bradykinin appeared only to release Ca²⁺ from intracellular stores. The possible role of protein kinase C (PKC) in modulating the [Ca²⁺] _i response to these agonists was examined by four methods. Low concentrations of TPA (2×10^–10 m) had no effect on Ca²⁺ release due to EGF, TGR- or bradykinin but resulted in a rapid return of [Ca²⁺] _i to baseline levels for EGF or TGF-. Addition of the PKC inhibitor staurosporine (1 and 10nm)_completely inhibited the action of TPA on EGF-induced [Ca²⁺] _i changes. An inhibitor of diglyceride kinase (R59022) mimicked the action of TPA. Down-regulation of PKC by overnight incubation with 0.1 or 1 m TPA produced the converse effect, namely prolonged Ca²⁺ entry following stimulation with EGF or TGF-. To show that one effect of TPA was on Ca²⁺ entry, fura-2 loaded cells were suspended in Mn²⁺ rather than Ca²⁺ buffers. Addition of EGF or TGF- resulted in Ca²⁺ release and Mn²⁺ entry. TPA but not the inactive phorbol ester, 4--phorbol-12,13-didecanoate, inhibited the Mn²⁺ influx. Thus, PKC is able to regulate Ca²⁺ entry due to EGF or TGF- in this cell type. A431 cells treated with higher concentrations of TPA (5×10^–8 m) inhibited not only Ca²⁺ entry but also Ca²⁺ release due to EGF/TGF- but had no effect on bradykinin-mediated Ca²⁺ release, suggesting differences in the regulation of the intracellular stores responsive to these two classes of agonists. Furthermore, sequential addition of EGF or TGF- gave a single transient of [Ca²⁺] _i , showing a common pool of Ca²⁺ for these agonists. In contrast, sequential addition of EGF (or TGF-) and bradykinin resulted in two [Ca²⁺] _i transients equal in size to those obtained with a single agonist. Ionomycin alone was able to fully deplete intracellular Ca²⁺ stores, whereas ionomycin following either EGF (or TGF-) or bradykinin gave an elevation of the [Ca²⁺] _i signal equal to that of the second agonist. These data indicate that there are separate pools of intracellular Ca²⁺ for EGF-mediated Ca²⁺ release which also respond differently to TPA.     

Ca2+和Sr2+诱导大肠埃希菌感受态细胞的形成及转化的影响

为研究金属离子诱导下感受态细胞形成的机理及揭示转化发生的机制,分别用Ca~(2+)和Sr~(2+)(0~140mmol/L)制备大肠埃希菌感受态细胞并转化。研究结果表明,不同浓度的Ca~(2+)和Sr~(2+)诱导的感受态细胞的效价不同,两种金属离子对大肠埃希菌细胞内外膜的通透性均有较大影响,但细胞内外膜的改变程度与转化率无直接关系;电镜结果显示,未处理的细胞呈簇聚集发生粘连现象,感受态细胞整体呈分散状态,局部发生聚集,而转化后的细胞独立存在,边缘异常清晰。     

Response of Cleopatra mandarin seedlings to a polyamine-biosynthesis inhibitor under salt stress

Six-month-old, uniform-sized seedlings of Cleopatra mandarin growing in hydroponics in Hoagland nutrient solution under glasshouse conditions were subjected to salinity treatment (NaCl 75 mM). Addition of NaCl to the nutrient medium reduced plant growth (shoot height and leaf number), leaf chlorophyll content, chlorophyll fluorescence yields (Fv/Fm), net photosynthesis, stomatal conductance, transpiration rate, intracellular CO₂ concentration, N, K⁺ and Ca²⁺ + Mg²⁺ contents of the leaves; and increased total putrescine (Put), proline and Na⁺ and Cl⁻ contents of the leaves. Addition of d-arginine (1 mM) to the saline medium further reduced the values of all the parameters except Fv/Fm, photosynthesis and related parameters and Ca²⁺ + Mg²⁺ contents of the leaves, and increased total spermine (Spm) content of the leaves. However, total Put contents were decreased; spermidine (Spd) contents and Na⁺ and Cl⁻ titres of the leaves were unaffected. Weekly spray of d-arginine (5 mM) was less harmful than its addition to the nutrient medium (1 mM). Addition of 0.5 mM Spd to the medium alleviated the adverse effects of d-arginine by improving plant growth, leaf chlorophyll content, total Put, Spd, Spm, N, P, K⁺ and Ca²⁺ + Mg²⁺ contents of the leaves. Weekly spray of Spd (5 mM) was less effective than its addition in the nutrient medium (0.5 mM).     

Physiological responses of four herbaceous plants to aluminum stress in South China

Different plants have physiological responses under Al stress, but there is no systematic study to examine physiological responses of herbaceous plants under Al stress. The aim of this study is to investigate the effect of Al on physiological characteristics of four herbaceous plants, which distributed in red soil area in South China, and to analyze the differences in physiological responses to Al stress between the four herbaceous plants. Four herbaceous plants (Pharbitis nil, Cassia occidentlis, Echinochloa colonum and Aeschynomene indica) were used, and the seed germination percentage, the contents of chlorophyll, proline, and malondialdehyde (MDA), membrane permeability (MP), soluble sugar, and activities of peroxides (POD) and catalase (CAT) in leaves under five Al³⁺ treatments (0, 80, 400, 2 000, and 10 000 mg/L) were assayed with the sand culture method. The results showed remarkable effects of Al³⁺ on physiological characteristics of these four herbaceous plants. The seeds of all the four species could not germinate at 10 000 mg/L, and the growth of all plants were retarded under the 2 000 mg/L Al³⁺ treatment. Compared with the control, 2 000 mg/L Al³⁺ significantly (P < 0.05) reduced the contents of chlorophyll a and chlorophyll a + b, and increased the contents of MDA and MP. The content of proline increased very significantly (P < 0.01) and activities of POD and CAT were depressed. The contents of MDA and MP in leaves of P. nil and A. indica decreased, and the activities of POD and CAT in leaves of the two plants increased under 80 mg/L and 400 mg/L. However, the changes in C. occidentlis leaves were opposite to those of the above two plants. The changes in leaves of E. colonum were similar to those of P. nil and A. indica at 80 mg/L, but were opposite to those at 400 mg/L Al³⁺. It is suggested that plants with higher activities of POD and CAT, more contents of chlorophyll and proline, and lower contents of MDA and MP consequently improve the tolerance to Al stress under low and middle Al treatments. __________ Translated from Acta Phytoecologica Sinica, 2005, 29(4): 644–651 [译自: 植物生态学报, 2005, 29(4): 644–651]