Institute of Plant Nutrition, Leibniz University of Hannover, Herrenhaeuser Str 2, 30419 Hannover, Germany.
Physiol Plant. 2010 Feb;138(2):176-90. doi: 10.1111/j.1399-3054.2009.01303.x. Epub 2009 Oct 6.
Two common bean (Phaseolus vulgaris L.) genotypes differing in aluminum (Al) resistance, Quimbaya (Al-resistant) and VAX-1 (Al-sensitive) were grown in hydroponics for up to 25 h with or without Al, and several parameters related to the exudation of organic acids anions from the root apex were investigated. Al treatment enhanced the exudation of citrate from the root tips of both genotypes. However, its dynamic offers the most consistent relationship between Al-induced inhibition of root elongation and Al accumulation in and exclusion from the root apices. Initially, in both genotypes the short-term (4 h) Al-injury period was characterized by the absence of citrate efflux independent of the citrate content of the root apices, and reduction of cytosolic turnover of citrate conferred by a reduced Nicotinamide adenine dinucleotide phosphate-isocitrate dehydrogenase (EC 1.1.1.42) activity. Transient recovery from initial Al stress (4-12 h) was found to be dependent mainly on the capacity to utilize internal citrate pools (Al-resistant genotype Quimbaya) or enhanced citrate synthesis [increased activities of NAD-malate dehydrogenase (EC 1.1.1.37) and ATP-phosphofructokinase (EC 2.7.1.11) in Al-sensitive VAX-1]. Sustained recovery from Al stress through citrate exudation in genotype Quimbaya after 24 h Al treatment relied on restoring the internal citrate pool and the constitutive high activity of citrate synthase (CS) (EC 4.1.3.7) fuelled by high phosphoenolpyruvate carboxylase (EC 4.1.1.31) activity. In the Al-sensitive genotype VAX-1 the citrate exudation and thus Al exclusion and root elongation could not be maintained coinciding with an exhaustion of the internal citrate pool and decreased CS activity.
两种不同耐铝基因型的普通菜豆（Phaseolus vulgaris L.），Quimbaya（耐铝）和 VAX-1（铝敏感），在水培条件下生长了长达 25 小时，有无铝处理，并研究了与根尖有机酸阴离子分泌有关的几个参数。铝处理增强了两种基因型根尖柠檬酸的分泌。然而，其动态提供了最一致的关系，即铝诱导的根尖伸长抑制与根尖积累和排斥铝之间的关系。最初，在两种基因型中，短期（4 小时）铝损伤期的特征是，无论根尖的柠檬酸含量如何，都没有柠檬酸外排，并且由于 NAD 磷酸异柠檬酸脱氢酶（EC 1.1.1.42）活性降低，柠檬酸的细胞质周转率降低。发现从最初的铝胁迫中短暂恢复（4-12 小时）主要依赖于利用内部柠檬酸池的能力（耐铝基因型 Quimbaya）或增强柠檬酸合成[增加 NAD-苹果酸脱氢酶（EC 1.1.1.37）和 ATP-磷酸果糖激酶（EC 2.7.1.11）的活性在铝敏感的 VAX-1 中]。在 Quimbaya 基因型中，经过 24 小时的铝处理后，通过柠檬酸分泌从铝胁迫中持续恢复，依赖于恢复内部柠檬酸池和组成型高柠檬酸合酶（CS）活性（EC 4.1.3.7），由高磷酸烯醇丙酮酸羧激酶（EC 4.1.1.31）活性驱动。在铝敏感的 VAX-1 基因型中，柠檬酸的分泌，因此铝的排斥和根的伸长不能维持，与内部柠檬酸池的耗尽和 CS 活性的降低相一致。
