磷对铝胁迫下荞麦元素吸收与运输的影响

以不同耐铝基因型江西养麦(耐性)和内蒙荞麦(敏感)为材料,采用土培法研究磷对铝胁迫下荞麦生长和Al,P等元素吸收、运输的影响.结果表明,铝胁迫下0.2 g/kg的磷能有效缓解铝毒对荞麦根长的抑制.培养30d后,0.4 g/kg磷处理能显著降低铝在荞麦根系和地上部的积累.铝胁迫下加磷可影响养麦体内Ca,Mg,Mn,Zn,Fe的吸收,0.4 g/kg铝配施0.4 g/kg磷处理对荞麦根系Ca,Mg吸收最有利,内蒙荞麦根系Mg的含量比不加磷组提高了76.8%,但显著阻碍了铝胁迫下荞麦体内Ca,Fe的向上运输.铝胁迫下配施磷促进荞麦根系对Zn,Fe吸收,有利于Zn向地上部转运.施磷能有效缓解铝毒对荞麦生长的抑制,降低根系和地上部铝含量,有利于Ca,Mg,Mn,Zn,Fe的吸收和Mg,Zn的运输.     

小麦根尖细胞壁对铝的吸附/解吸特性及其与耐铝性的关系

研究了耐铝性明显差异的2个小麦基因型西矮麦1号(耐性)和辐84系(敏感)根系对铝毒胁迫的反应与根尖细胞壁组分以及细胞壁对铝的吸附和解吸的关系。结果表明,30mol/L.AlCl3可迅速抑制小麦根系伸长,但对辐84系根系伸长的抑制更为明显,且小麦根系相对伸长率随着铝浓度的提高而急剧降低。在30mol/L.AlCl3处理24h后,西矮麦1号根系伸长的抑制率为33.3%,而辐84系根系伸长的抑制率高达70.9%。小麦距根尖0～10.mm根段的铝含量和细胞壁中果胶糖醛酸含量显著高于10～20.mm根段,且前者对铝的累积吸附量明显大于后者;在0～10.mm根段,敏感基因型果胶含量高于耐性基因型,其根尖含铝量及根尖细胞壁对铝的吸附量都要大于后者。采用1.0.mol/L.NH3.H2O对细胞壁预处理2.h降低果胶甲基酯化程度后,耐性和敏感基因型根尖细胞壁对铝的累积吸附量分别降低了17.1%和20.9%,但对铝的累积解吸率没有影响。由此可见,小麦根尖是铝毒的主要位点,细胞壁果胶含量和果胶甲基酯化程度可能是导致不同小麦基因型根尖细胞壁对铝吸附量、铝积累量的差异及其对铝毒胁迫反应的差异的重要原因。     

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。     

铝胁迫下硝普钠对黑麦和小麦根尖细胞壁铝吸附的影响

用一氧化氮供体硝普钠(sodium nitroprusside,SNP)处理铝胁迫下的黑麦和小麦幼苗,探讨铝胁迫和铝胁迫下外源NO对黑麦和小麦根尖细胞壁铝吸附的影响。结果表明:铝显著抑制黑麦和小麦根的伸长生长,小麦受抑制更为严重;SNP处理可缓解铝对黑麦和小麦根伸长生长的抑制作用,1 mmol/L SNP处理最有效。小麦根尖对铝的吸附量和吸附速率显著高于黑麦的,1 mmol/L SNP处理显著降低小麦和黑麦细胞壁对铝的吸附量,使根尖铝含量显著下降。铝与根尖细胞壁的结合是导致植物铝毒害的重要原因,而降低根尖细胞壁对铝的吸附是外源NO缓解铝毒害的重要机制。     

铝对小麦根尖细胞壁过氧化物酶活性和过氧化氢含量的影响

以2个小麦基因型鉴-864(耐性)和扬麦5号(敏感)为材料,采用溶液培养方法研究了铝胁迫下小麦根系伸长、根尖铝含量、根尖细胞壁过氧化物酶活性和H2O2含量的变化。结果表明,随着铝浓度的提高,小麦根系伸长受铝抑制程度加剧,根尖铝含量也明显升高;但敏感基因型根尖铝含量较高,根系伸长受抑程度更为明显。在铝胁迫下,2个小麦基因型根尖可溶态愈创木酚过氧化物酶(GPX)和松柏醇过氧化物酶(CAPX)活性没有显著变化,细胞壁离子键结合态GPX和CAPX的活性则随着铝浓度的提高而显著升高,H2O2含量也呈现类似的趋势;而敏感基因型过氧化物酶活性升高和H2O2积累更为明显。因此,铝胁迫下,小麦敏感基因型根尖细胞壁离子键结合态GPX和CAPX活性升高而引起H2O2积累,促进根系木质化和细胞壁氧化交联,导致根细胞壁刚性提高而伸展能力降低,是其根系伸长受到严重抑制的原因。     

钙、硅对铝胁迫下荞麦光合生理的影响

采用营养液培养法,研究了钙、硅对荞麦根长、光合作用和叶绿素荧光的影响。结果表明,15 d时0.5 mmol/L和5 mmol/L Al3 处理降低了荞麦根长、叶绿素含量、净光合速率(Pn)、气孔导度(Ci),对叶绿素荧光Fv/Fm、Fv/Fo的影响不大,30 d后以上伤害均加重。配施钙或硅的处理,能促进根的伸长和提高叶绿素含量,并使叶片的Pn、Ci保持在较高的水平,施硅能明显提高荞麦叶片的叶绿素荧光Fv/Fm、Fv/F,而钙的影响不大。硅对铝胁迫的缓解效果好于钙。     

硅对减轻水稻的铝胁迫效应及其机理研究

通过分析溶液中Al离子形态变化和根内Al的分布 ,探讨Si对减轻水稻Al胁迫的效应及其机理。结果表明 ,pH4.5的溶液培养条件下Al在短时间内即可明显地抑制水稻根系的生长 ,加入不同形态的硅酸可有效地减轻Al对水稻的胁迫 ,根的伸长量接近或达到对照处理的水平。加Si降低了溶液中单质态Al离子的浓度 ,改变了溶液中Al的形态。分子筛柱层析分离和离子交换树脂吸附分析发现 ,溶液中产生了新的Al化合物 ,阳离子交换态Al的比率由 78%降低到 48% ,而交换态Si的比率由 0 %增加到 20%。Al主要聚集于根质外体特别是细胞壁中 ,加入低分子态硅酸增加了根全Al和质外体Al的含量 ,但是却降低了细胞壁Al的含量 ,而加入高分子态硅酸明显地降低了根全Al、质外体、共质体和细胞壁Al的含量     

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。     

蓼科、禾本科植物细胞膜对铝胁迫反应的比较研究

以4种蓼科植物(荞麦、金荞麦、虎杖、无辣蓼)和2种禾本科植物(水稻、小麦)为材料,比较研究不同科属植物的细胞膜对铝胁迫反应的差异。结果表明:(1)6种植物叶片的游离脯氨酸含量、MDA含量和根系质膜透性均随着Al3 胁迫浓度增加而增大,禾本科植物的游离脯氨酸含量高于4种蓼科植物,荞麦、金荞麦的质膜透性、MDA含量高于虎杖、无辣蓼、水稻、小麦。(2)荞麦、小麦叶片的SOD和POD活性随Al3 胁迫浓度持续增长,虎杖和水稻持续下降,金荞麦和无辣蓼在25 mg/L Al3 处理时最高,100 mg/L Al3 胁迫明显降低。综合细胞膜对铝胁迫反应的各种特征,可以说明蓼科植物细胞膜透性变化是Al3 引发氧化胁迫的一种受损表现,而禾本科植物细胞膜透性变化是对A3 胁迫的一种适应性反应。     

铝胁迫下植物根尖细胞壁组成物质变化抑制根伸长的生理机制研究

根伸长受抑制是植物受铝毒害的主要症状,铝诱导的细胞壁组成物质的变化是其主要原因。本文主要对铝胁迫下植物根尖细胞壁组成物质如木质素、 胼胝质、 纤维素、 半纤维素、 果胶、 细胞壁多糖蛋白及相关代谢酶类在铝胁迫下的变化对根伸长的影响及生理机理的研究进展进行了综述,明确了铝胁迫诱导的植物根尖细胞壁组成物质含量、 比例及结构的变化导致细胞壁刚性降低,从而抑制细胞伸长,最终抑制根伸长。本文还指出,鉴于缺乏对同一植物甚至同一个种类的植物根尖细胞壁各主要组成物质铝胁迫下变化的系统研究,不能对造成该植物根伸长受抑制的原因做出全面合理的解释,所以今后应侧重于铝胁迫下各细胞壁组分变化在抑制根伸长中的贡献率的研究,尤其要针对主要粮食作物进行系统研究,以有效解决铝胁迫造成的产质量降低。     

Genotypic Differences Among Plant Species in Response to Aluminum Stress

Abstract

Genotypic differences in aluminum (Al) resistance in rye (Secale cereale L.), triticale (X Triticosecale Wittmack), wheat (Triticum aestivum L.), and buckwheat (Fygopyrum esculentum Moench) were examined using a compartmental hydroponic system. Four-day-old seedlings were grown for 24 h in 0.5 mM CaCl₂ (pH 4.5) containing 0 or 50 μM Al. Relative root elongation (RRE) at 50 μM Al. (as a percentage of that at 0 Al) was used as the index of Al resistance. On average, rye exhibited the highest Al resistance, followed by buckwheat, triticale, and wheat. However, triticale displayed the greatest genotypic differences. Al content in the root tips of triticale breeding lines negatively correlated with RRE (r = 0.5, P < 0.01), implying that the Al exclusion mechanism contributed to Al resistance. Furthermore, high Al resistance in buckwheat correlated well with the growth habitats of buckwheat, indicating that adaptation mechanisms giving good Al resistance have evolved in buckwheat. All of these results suggested that it is possible to obtain greater Al resistance in plants by screening current existing cultivars. The selection of new cultivars with increased Al resistance and sensitivity will provide important material for further studies exploring Al phytotoxic and resistant mechanisms.     

Aluminum effects on nitrate uptake and reduction in sorghum

The effects of Al on nitrate uptake and on the activity of the nitrate reductase (NR) in two hybrid cultivars of sorghum (Sorghum bicolor (L.) Moench) differing in Al tolerance were studied. The nitrate uptake by intact root system was strongly reduced by Al in both cultivars, but mainly in the Al‐sensitive cultivar. The kinetic constants also changed in the presence of Al: Vmax decreased 98% and 71% and Km increased 267% and 42% in the Al‐sensitive and Al‐tolerant cultivar, respectively. Aluminum reduced the in vitro NR activity on the roots and shoots of both cultivars, especially of the Al‐sensitive cultivar. Aluminum added to the nutrient solution or to the reaction mixture, however, inhibited differentially the NR of the roots and shoots, indicating marked differences between the enzymes from these two tissues. Aluminum reduced the Vmax but did not affect the Km of nitrate activation of the shoot NR. Therefore, Al inhibition of the NR was non‐competitive and could not be reversed by increasing nitrate concentration. Aluminum not only reduced the nitrate uptake but also had a direct effect on the NR and consequently on nitrate reduction. A correlation between NR tolerance to Al and plant tolerance to Al was observed.     

硅、钙对水土保持植物荞麦铝毒的缓解效应

采取水培法,研究了铝胁迫下不同水平的钙或硅对荞麦真叶期和初花期铝毒害的缓解效应。结果显示:在Al3 胁迫下,增加钙或硅的供应可减轻Al3 对植物的毒害,显著削弱因Al3 处理导致的根系活力、可溶性蛋白质含量和过氧化物酶(POD)活性的下降以及丙二醛含量的上升,在初花期能完全消除Al3 对可溶性蛋白质形成的抑制效应并促进其形成,有效提高植株抗逆性。但随着Al3 浓度的提高,Ca2 和硅的缓解效应有限。Ca2 的缓解效果略强于硅。     

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.     

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

Abstract

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.     

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     

Influence of Aluminum on the Growth and Organic Acid Exudation in Alfalfa Cultivars Grown in Nutrient Solution

A study was conducted to evaluate the effects of aluminum (Al) in nutrient solutions on the dry weight (DW) yield, Al and phosphorus (P) contents, and organic acid exudation in alfalfa (Medicago sativa L.). Four alfalfa cultivars (‘Robust’, ‘Sceptre’, ‘Aquarius’, and ‘California-55’) were grown in nutrient solution at pH 4.5 and 6.0, with (50 and 100 μM) and without Al. The results revealed that Al caused a significant reduction in DW, especially in pH 4.5 treatment. Organic acid exudation was affected by pH and Al treatments. Citrate and succinate exudation increased with the high Al treatment at pH 4.5. However, no relationship between pH and carboxylate exudation was observed at pH 6.0. Accumulation of P and Al in roots suggests the existence of an exclusion mechanism for Al in alfalfa. Selection of cultivars with enhanced organic exudation capacity in response to Al might be useful for alfalfa production in moderately acidic soils.     

高铝低磷胁迫对胡枝子生长及矿质元素吸收的影响

限制酸性土壤作物生长的最重要、最普遍的因子是Al3+ 的毒害和 P 的缺乏.本文用溶液培养试验研究两种不同生态型的二色胡枝子在高Al低P胁迫下的矿质营养元素积累情况.试验表明,江西胡枝子比河北胡枝子更耐低 P 低 pH 的生长环境,但两者间耐Al性无显著差异;100 μm/L Al 处理显著地抑制了两种胡枝子对 Ca 的吸收,降低了根系 Mg 的积累量,对植株的 K、P、Fe、Zn、Cu 含量没有显著影响;低 P 处理没有显著降低两种胡枝子对 Ca、K、Fe、Zn、Cu 和江西胡枝子对 Mg 的吸收,但是低 P 处理显著降低了河北胡枝子对 Mg 的吸收和转运.二色胡枝子植株吸收的 Al 主要积累在根部,地上部分Al含量仅是根系的1% 左右.     

Differential Aluminum Resistance and Organic Acid Anions Secretion in Triticale

Abstract

Triticale (X Triticosecale Wittmack), a hybrid of wheat and rye, shows a high degree of aluminum (Al) tolerance, but variation in Al resistance between cultivars does exist. The mechanisms responsible for differential Al resistance in 10 triticale cultivars were investigated in this study. Triticale roots secreted both malate and citrate in response to Al stress. The amount of organic acid anions secreted was correlated positively to the relative root elongation (an index for Al resistance) and negatively to the Al content in root apices under Al stress, suggesting that the secretion of malate and citrate seems to be involved in the exclusion of Al from root tip. The Al‐induced secretion of malate and citrate was characterized using an Al‐resistant cultivar (ZC 237) and an Al‐sensitive cultivar (OH 1621). Root elongation was significantly inhibited in both ZC 237 and OH 1621 after 24 h of exposure to 30, 50, or 100 µM Al but was more strongly in OH 1621 than in ZC 237 at all Al concentrations tested. A marked lag phase (3 h) between the addition of Al and the secretion of organic acid anions was observed in both triticale cultivars, and the secretion increased with increasing external Al concentration. The two anion‐channel inhibitors, phenylglyoxal and niflumic acid, significantly inhibited the secretion of malate and citrate in ZC 237, with the degree of the inhibition of niflumic acid greater than that of phenylglyoxal. The Al‐induced secretion of malate and citrate decreased to a very low level at low temperature (4°C) in both cultivars. These results indicate that Al‐induced malate and citrate secretion from roots play important roles in excluding Al and thereby detoxifying Al in triticale. The Al‐induced organic acid anions were inhibited by anion‐channel inhibitors and were dependent on temperature.