黑麦品种间耐铝差异性机制研究

采用室内模拟方法,研究了铝诱导黑麦根系分泌有机酸、根尖磷对铝的固定作用。结果表明,在铝胁迫下冬牧品种（Win）相对根伸长率高于King品种。在铝胁迫下,经磷预处理的根尖铝和磷含量增加,且以Win品种根尖中的Al、P含量较高,说明根尖磷对铝的固定是黑麦耐铝机制之一。另一方面,在铝胁迫下,两品种根系均分泌柠檬酸和苹果酸,且Win的分泌速率较高。有机酸的分泌随着铝处理浓度（10、30、50 mol/L）和时间（0.5、3、6、9、12 h）的增加而增加,但在低温（4C）下柠檬酸分泌量显著减少。Al处理0.5 h后苹果酸已明显分泌,而柠檬酸的分泌在铝处理6 h后才明显增加。在铝处理前,进行缺磷预处理（3 d）不能增加有机酸的分泌,10 mol/L的La3+、Cu2+、Ni3+也不能诱导根系分泌有机酸。说明铝诱导根系专一性分泌有机酸也是黑麦品种间耐铝性差异的机制。     

铝胁迫下萹蓄与饭豆根系有机酸分泌特性比较

以蓄和饭豆为试验材料,从对Al胁迫的响应时间、蛋白质合成抑制剂的影响、体内有机酸含量变化及阴离子通道抑制剂的影响等方面,比较研究了Al诱导根系分泌有机酸的差异,以进一步明确铝(Al)诱导植物根系有机酸分泌的过程。结果表明,萹蓄根系在Al胁迫后30.min内分泌出草酸,而Al胁迫至少4.h后饭豆根系才开始分泌柠檬酸;蛋白质合成抑制剂环己亚酰胺(Cycloheximide,CHM)不影响萹蓄根系草酸的分泌,但抑制了84%Al诱导的饭豆根系柠檬酸的分泌,表明前者不需要新蛋白质的诱导合成,却是后者所必需的。Al处理不改变萹蓄根尖草酸的含量,但明显提高了饭豆根尖柠檬酸的含量;阴离子通道抑制剂苯甲酰甲醛(Phenylglyoxal,PG)和蒽-9-羧酸(Anthrancene-9-carboxylic.acid,A-9-C)分别有效抑制Al诱导萹蓄根系草酸的分泌及饭豆根系柠檬酸的分泌,再次证明两者有机酸的分泌是通过某种被Al所诱导或激活的阴离子通道所实现的。     

干旱胁迫及复水对豌豆根系内源激素含量的影响

采用盆栽试验方法,研究了干旱胁迫及复水对豌豆根系脱落酸(ABA)、吲哚乙酸(IAA)、赤霉素(GA)和玉米素(ZT)等4种内源激素含量的影响.结果表明:不同程度的干旱胁迫均导致各生育期豌豆根系ABA和IAA含量增加,GA和ZT含量减少,且随干旱胁迫程度的加重变化量增大.同时对各生育期豌豆根系内源激素比例产生影响,对ZT与ABA、GA与ABA、GA与IAA、ZT与IAA比例影响较大,对ZT与GA、IAA与ABA比例影响较小.旱后复水可对各生育期豌豆根系内源激素含量产生补偿效应,其补偿量决定于豌豆生育时期、干旱胁迫强度和复水历时.同时促进各生育期豌豆根系内源激素比例发生变化.     

镉胁迫对大豆幼苗生理特性的影响

为了探明镉胁迫对作物生理特性的影响,对镉胁迫下大豆叶片镉含量、光合参数、内源激素含量、生长参数变化及内源激素调控气孔开度与光合碳同化的生理机制进行了分析。结果表明:镉胁迫导致了大豆叶片脱落酸(ABA)含量的升高与玉米素核苷(ZR,细胞分裂素的一种)含量的降低,ABA/ZR升高进一步诱导了气孔收缩。镉胁迫初期,大豆叶片气孔导度、光合速率与胞间CO₂浓度均呈现出降低的趋势,表明此时气孔因素是限制大豆光合碳同化的主要因素。随着镉处理时间的延长,叶片镉离子含量逐渐升高,对叶肉细胞造成离子毒害。镉胁迫9 d后,虽然大豆的气孔导度与光合速率降低,但胞间CO₂浓度呈现出升高趋势,此时非气孔因素是限制光合碳同化的主要因素。最终,长期镉胁迫导致了大豆幼苗株高、叶面积与根干重较对照显著降低。     

铝胁迫对不同耐铝大麦基因型干物质积累与铝和养分含量的影响

以苗期表现为耐铝性具有明显差异的 10份大麦基因型为材料 (耐铝和铝敏感基因型各 5个 ) ,研究铝胁迫条件下生育后期植株生物量、铝和养分元素含量的差异。结果表明 ,铝胁迫抑制植株干物质积累 ,但抑制程度因基因型而异 ,上 70 119等铝敏感基因型受影响较大 ,且两类基因型之间的差异成熟期明显大于乳熟期。铝胁迫显著降低敏感基因型的子粒产量 ,但对耐性基因型的影响较小。铝胁迫增加所有基因型根系和地上部的Al含量 ,但增加幅度基因型之间存在着明显差异 ,耐铝基因型增加较少 ,而铝敏感基因型表现显著增加。酸性土壤上 ,根系和地上部N、P、K、Ca、Mg和Zn等养分含量 ,铝敏感基因型显著减少 ,耐铝基因型受影响较小。     

续断菊与玉米间作的铅累积及根系低分子量有机酸分泌特征研究

为探明间作作物根系分泌低分子量有机酸对土壤重金属生物有效性的影响,采用矿区周边农田土壤进行室内盆栽试验,研究了云南本土超累积植物续断菊(Sonchus asper L. Hill)和玉米(Zea mays L.)间作下,植物生长、根系低分子量有机酸分泌量、根际土壤Pb提取形态以及植物Pb积累特点。结果表明:与单作相比,间作续断菊地上部和根部生物量、根长、根内径和根系体积均显著增加(P0.05);间作玉米根部生物量、根长、根内径和根系体积显著增加(P0.05)。柠檬酸、草酸是续断菊和玉米根系分泌的主要低分子量有机酸,间作导致续断菊根系低分子量有机酸的分泌量增加,玉米根系低分子量有机酸的分泌量降低。续断菊根际土壤生物有效态Pb含量增加85.2%(P0.05),而玉米根际土壤生物有效态Pb含量降低26.1%(P0.05)。续断菊体内Pb含量显著增加18.0%～43.2%(P0.05),富集系数提高26.0%,而转运系数降低42.0%;玉米地上部Pb含量显著降低24.3%(P0.05),转运系数降低43.1%。续断菊根系分泌的柠檬酸和草酸数量,均与土壤生物有效态Pb含量呈显著正相关,且土壤有效态Pb含量分别与续断菊地上部和根部的Pb含量呈显著正相关。表明间作增加了续断菊对Pb的吸收积累量,与间作体系植物根系分泌的低分子有机酸介导下的土壤有效态Pb含量增加密切相关。     

铝胁迫下不同小麦基因型根际pH的变化、NH4+和NO3-吸收及还原与其耐铝性的关系

以耐Al性明显差异的 2个小麦基因型为材料 ,采用溶液培养试验和动力学方法研究了根际 pH变化、NH4+和NO3- 的吸收以及NO3- 还原与其耐Al性的关系。结果表明 ,A1胁迫下鉴 86.4(耐性基因型 )比扬麦 5号 (敏感基因型 )能维持较高的根际 pH值 ,当溶液 pH值下降到最低时 ,前者比后者高 0.23个pH单位。吸收动力学研究表明 ,鉴 86-4在无Al和有Al胁迫时对NO3- 的吸收速率和亲和力大于扬麦 5号 ;而对NH4+的吸收速率和亲和力却小于扬麦 5号。Al还降低叶片和根系的硝酸还原酶活性 ,但鉴 86.4的叶片和根系硝酸还原酶活性均高于扬麦 5号。此外 ,在Al胁迫下 ,植株体内游离脯氨酸含量迅速提高 ,但扬麦 5号积累量高于鉴 86.4。鉴 86.4具有较高的耐Al能力可能与其在Al胁迫下对NO3- 的吸收速率、亲和力以及硝酸还原酶活性较高 ,而对N4+的吸收速率和亲和力较低 ,从而能维持较高的根际 pH值有关     

铝诱导大豆根系有机酸分泌的能量消耗的定量研究

铝诱导大豆根系有机酸分泌是其解铝毒的一种重要机制,该过程需要消耗能量,然而有关能量消耗的定量研究还未见报道。本文比较了铝胁迫条件下,两个大豆品种根尖有机酸分泌、 腺苷酸、 无机磷、 细胞质pH值等指标的变化。结果表明,铝处理（25 mol/L）明显诱导大豆根系苹果酸和柠檬酸的分泌。与对照相比,铝胁迫条件下中豆32和本地2号的根尖ATP含量分别降低40.1%和13.2%,根系细胞质子跨膜电化学势差分别增加1711.8和570.6 J/mol,然而,根尖无机磷浓度变化差异不大。运用Nernst-Gibbs方程定量计算自由能变化,发现中豆32和本地2号根尖细胞自由能分别消耗16.13 kJ/mol和14.59 kJ/mol, 中豆32分泌单位苹果酸和柠檬酸的能量消耗分别为0.96 kJ/mol和3.15 kJ/mol,本地2号则为2.01 kJ/mol和5.68 kJ/mol。这表明不同耐铝性大豆品种分泌有机酸消耗的能量存在差异,该结果为筛选耐铝作物品种提供了新思路。     

铝胁迫下黑麦根尖分泌有机酸和钾离子的研究

采用药理学研究方法,研究了几种抑制剂和脱落酸对铝诱导黑麦根尖分泌有机酸和钾离子的影响。结果表明,在铝(100、200、300μmol/L AlCl3)胁迫下,根尖分泌柠檬酸、苹果酸和钾离子,且随着铝处理浓度的增加其分泌量显著增加。阴离子通道抑制剂苯甲酰甲醛(0.1、0.2 mmol/L)抑制根尖在铝(200μmol/L AlCl3)胁迫下分泌有机酸的同时,也抑制根尖分泌钾离子;钾离子通道抑制剂四乙基铵(20、40 mmol/L)和铯(10、20 mmol/L CsCl)在抑制根尖分泌钾离子的同时,也抑制铝诱导的有机酸分泌。25、50μmol/L的ABA处理后,铝诱导的有机酸分泌和钾离子的分泌均显著增加。但是,铝诱导的有机酸分泌在受到阴离子通道抑制剂尼氟灭酸(0.4、0.8 mmol/L)处理抑制后,钾离子的分泌并不减少;铝胁迫下根尖分泌的钾离子在ATP酶抑制剂钒酸钠(0.25、0.50、2.00 mmol/L)处理后受阻的同时,有机酸的分泌却显著增加。这些结果说明,钾离子是铝诱导黑麦根尖分泌有机酸的陪伴离子,而并非有机酸分泌的调控因子。     

诱抗剂对水稻幼苗耐盐性的诱导作用

本试验对水稻幼苗做诱抗剂处理并进行盐胁迫,测定了不同品种幼苗各性状耐盐性诱导率,并进一步对品种R6幼苗的生理特性分析。结果表明,诱抗剂对不同水稻品种幼苗的耐盐性诱导率有明显差异,品种R6的根长诱导率最高;用诱抗剂处理水稻品种R6后,耐盐能力比盐胁迫对照显著提高,表现为增加了根系活跃吸收表面积、叶绿素含量和可溶性糖含量,明显增强了根系活力,降低丙二醛含量。诱抗剂还具有调节IAA和ABA内源激素含量及其分布的作用。     

Combined Effect of Short-Term Water Deficit Stress and Aluminum Toxicity on Citrate Secretion from Soybean Roots

Abstract

In order to investigate the combined effect of drought stress and aluminum (Al) toxicity on citrate exudation in soybean, hydroponic cultivation with addition of Al and PEG-6000 was conducted to simulate Al-toxic dry soil. Results showed that 2-day exposure of soybeans to 5.5% (w/v) PEG-6000 or 100 µM AlCl₃ mainly hindered root growth, while combined exposure to PEG and Al (PEG/Al) reduced both root and shoot growth. Photosynthetic rate of first trifoliolate for the Al-tolerant genotype PI 416937 (PI) was not affected by imposition of 5.5% PEG/100 µM AlCl₃ (38–40 h), whereas photosynthetic rate for the Al-sensitive genotype YC was significantly reduced. Based on root fresh weight, Al-induced citrate exudation in the roots of soybean genotypes recovered from pre-treatment with 5.5 or 9% PEG was not altered, but was increased in the plants pretreated with 7% PEG without recovery. After 2 days of recovery from 2-day combined exposure to 5.5% PEG/100 µM AlCl₃, the Al-tolerant PI exuded more citrate than its control, but the Al-sensitive YC exuded significantly less citrate than its corresponding control. Split root experiment revealed that Al-induced citrate exudation in one half of the root system was significantly reduced by exposing the other half of the root system to 0.5 mM CaCl₂ solution containing 9% PEG or 9% PEG/50 µM AlCl₃. However, organic acid secretion was not observed in the half of the root system in the Ca solution when the other part of the root system was exposed to the Ca solution containing 50 µM AlCl₃, 9% PEG or 9% PEG/50 µM AlCl₃. This suggests that no Al- or drought-induced signals such as ABA are involved in the citrate secretion in soybean.     

铝和镉胁迫对两个大麦品种矿质营养和根系分泌物的影响

A hydroponic experiment was carried out to study the effect of aluminum （Al） and cadmium （Cd） on Al and mineral nutrient contents in plants and Al-induced organic acid exudation in two barley varieties with different Al tolerance. Al- sensitive cv. Shang 70-119 had significantly higher Al content and accumulation in plants than Al-tolerant cv. Gebeina, especially in roots, when subjected to low pH （4.0） and Al treatments （100 μmol L^-1 Al and 100 μmol L^-1 Al ＋1.0 μmol L^-1 Cd）. Cd addition increased Al content in plants exposed to Al stress. Both low pH and Al treatments caused marked reduction in Ca and Mg contents in all plant parts, P and K contents in the shoots and leaves, Fe, Zn and Mo contents in the leaves, Zn and B contents in the shoots, and Mn contents both in the roots and leaves. Moreover, changes in nutrient concentrations were greater in the plants exposed to both Al and Cd than in those exposed only to Al treatment. A dramatic enhancement of malate, citrate, and succinate was found in the plants exposed to 100 μmol L^-1 Al relative to the control, and the Al-tolerant cultivar had a considerable higher exudation of these organic acids than the Al-sensitive one, indicating that Al-induced enhancement of these organic acids is very likely to be associated with Al tolerance.     

Citrate Secretion Induced by Aluminum Stress May Not be a Key Mechanism Responsible for Differential Aluminum Tolerance of Some Soybean Genotypes

Abstract

Eighteen soybean genotypes differing in aluminum (Al) tolerance were used to investigate genotypic differences in Al-induced citrate exudation and its role in Al tolerance. Aluminum accumulation and localization in soybean roots were examined by analysis of total Al and hematoxylin staining. Soybean genotypes exhibited a wide range of Al tolerance. Based on relative root elongation, several Al-tolerant genotypes from Brazil such as B1, B10, and B15 were more tolerant than the Al-tolerant PI 416937 (PI) and Perry. All soybeans exuded citrate in response to Al stress, and some Al-sensitive genotypes secreted more citrate than tolerant ones, showing no correlation between the Al tolerance and Al-induced citrate exudation. Further study found that both copper (Cu) and cadmium (Cd) stimulated citrate and malate exudation in soybean, indicating that organic acid secretion is not specifically induced by Al. Aluminum concentrations were significantly higher in 2–3 and 3–4 cm of segments than that in 0–1 and 1–2 cm segments under 15 μM AlCl₃. Both the root mature zone and apex were heavily stained by hematoxylin after exposure to 10, 15, or 20 μM AlCl₃ (24 h), whereas root elongation zone was not stained. After exposure to 50 μM AlCl₃ for 20 min, the Al-tolerant PI was less stained by hematoxylin than the Al-sensitive Young, suggesting that Al accumulation in root apices seem to be an immediate response to Al stress, and related to differential Al sensitivity. Present results suggest that citrate secretion induced by Al stress may not be a key mechanism responsible for the differential Al tolerance of some soybean genotypes and other mechanism(s) conferring Al exclusion should exist and operate immediately after exposure to Al stress.     

小麦的铝毒及耐性

为探明Al的毒性和忍耐机理 ,比较了Scout 66和Atlas 66Al敏感和抗性的 2个小麦品种的根对Al的积累模式、根细胞壁对Al的吸附以及Al诱导的有机酸的分泌。结果表明 ,Al对Scout 6 6根伸长的抑制作用较Atlas 66明显。根系吸收的Al主要积累于 0至 5mm根尖处。Scout 6 6的根尖及Al处理后分离的根尖细胞壁对Al的积累量大于Atlas 6 6。但是 ,Al处理前分离根尖细胞壁 ,Al处理后细胞壁对Al的吸附量两品种间无显著差异。Al可诱导Atlas 6 6的根系分泌苹果酸 ,而Scout 6 6的分泌物中未发现Al诱导的有机酸。这些结果表明 ,Atlas 6 6的根尖及其细胞壁较Scout 66积累较少的Al,这种差异与Al诱导的有机酸分泌有关 ,而与根尖细胞壁固有的吸附Al的能力无关     

Aluminum tolerance of two wheat cultivars (Brevor and Atlas66) in relation to their rhizosphere pH and organic acids exuded from roots

Phytotoxicity of aluminum (Al) has become a serious problem in inhibiting plant growth on acid soils. Under Al stress, the changes of rhizosphere pH, root elongation, absorption of Al by wheat roots, organic acids exuded from roots, and some main factors related to Al-tolerant mechanisms have been studied using hydroponics, fluorescence spectrophotometry, and high performance liquid chromatography (HPLC). Two wheat cultivars, Brevor and Atlas66, differing in Al tolerance are chosen in the study. Accordingly, the rhizosphere pH has a positive effect on Al tolerance. Atlas66 (Al-tolerant) has higher capability to maintain high rhizosphere pH than Brevor (Al-sensitive) does. High pH can reduce Al3+ activity and toxicity, and increase the efficiency of exuding organic acids from the roots. More inhibition of root elongation has been found in Brevor because of the exposure of roots to Al3+ solution at low pH. Brevor accumulate more Al in roots than Atlas66 even at higher pH. Al-induced exudation of malic and citric acids has been found in Atlas66 roots, while no Al-induced organic acids have been found in Brevor. These results indicate that the Al-induced secretion of organic acids from Atlas66 roots has a positive correlation with Al tolerance. Comprehensive treatment of Al3+ and H+ indicates that wheat is adversely influenced by excess Al3+, rather than low pH.     

Aluminum tolerance associated with enhancement of plasma membrane H+-ATPase in the root apex of soybean

Seventeen soybean cultivars were screened to discern differences in aluminum (Al) sensitivity. The Sowon (Al-tolerant) and Poongsan (Al-sensitive) cultivars were selected for further study by simple growth measurement. Aluminum-induced root growth inhibition was significantly higher in the Poongsan cultivar than in the Sowon cultivar, although the differences depended on the Al concentration (0, 25, 50, 75 or 100 μmol L^–1) and the amount of exposure (0, 3, 6, 12 or 24 h). Damage occurred preferentially in the root apex. High-sensitivity growth measurements using India ink implicated the central elongation zone located 2–3 mm from the root apex. The Al content was lower 0–5 mm from the root apices in the Sowon cultivar than in the apices of the Poongsan cultivar when exposed to 50 μmol L^–1 Al for 12 h. Furthermore, the citric acid exudation rate was more than twofold higher in the Sowon cultivar. Protein production of plasma membrane (PM) H⁺-ATPase from the root apices (0–5 mm) was upregulated in the presence of Al for 24 h in both cultivars. This activity, however, decreased in both cultivars treated with Al and the Poongsan cultivar was more severely affected. We propose that Al-induced growth inhibition is correlated with changes in PM H⁺-ATPase activity, which is linked to the exudation of citric acid in the root apex.