Jemo Martin, Abaidoo Robert Clement, Nolte Christian, Horst Walter Johannes
International Institute of Tropical Agriculture, Humid Forest Ecoregional Centre, (Messa) Yaoundé, Cameroon.
J Plant Physiol. 2007 Apr;164(4):442-51. doi: 10.1016/j.jplph.2005.12.010. Epub 2006 Mar 29.
Plants growing in acid soils suffer both phosphorus (P) deficiency and aluminum (Al) toxicity stresses. Selection of genotypes for adaptation to either P deficiency or Al toxicity has sometimes been unsuccessful because these two soil factors often interact. Two experiments were conducted to evaluate eight cowpea genotypes for Al resistance and to study the combined effect of P deficiency and Al toxicity stress on growth, P uptake, and organic acid anion exudation of two genotypes of contrasting Al resistance selected from the first experiment. Relative root inhibition by 30 microM Al ranged from 14% to 60% and differed significantly among the genotypes. Al significantly induced callose formation, particularly in Al-sensitive genotypes. P accumulation was significantly reduced (28% and 95%) by Al application for both the Al-resistant and the Al-sensitive genotypes. Al supply significantly enhanced malate release of root apices of both genotypes. However, the exudation rate was significantly higher in the Al-resistant genotype. P deprivation induced an enhanced malate exudation in the presence of Al only in the Al-resistant genotype IT89KD-391. Citrate exudation rate of the root apices was lower than malate exudation by a factor of about 10, and was primarily enhanced by P deficiency in both genotypes. Al treatment further enhanced citrate exudation in P-sufficient, but not in P-deficient plants. The level of citrate exudation was consistently higher in the Al-resistant genotype IT89KD-391 particularly in presence of Al. It is concluded that the Al-resistant genotype is better adapted to acid Al-toxic and P-deficient soils than the Al-sensitive genotype since both malate and citrate exudation were more enhanced by combined Al and P-deficiency stresses.
生长在酸性土壤中的植物会遭受磷（P）缺乏和铝（Al）毒性胁迫。选择适应磷缺乏或铝毒性的基因型有时并不成功，因为这两个土壤因素常常相互作用。进行了两项实验，以评估8种豇豆基因型的耐铝性，并研究磷缺乏和铝毒性胁迫对从第一个实验中选出的两种耐铝性不同的基因型的生长、磷吸收和有机酸阴离子分泌的综合影响。30微摩尔铝对根系的相对抑制率在14%至60%之间，不同基因型之间差异显著。铝显著诱导胼胝质形成，尤其是在铝敏感基因型中。施用铝后，耐铝和铝敏感基因型的磷积累均显著降低（分别降低28%和95%）。供应铝显著增强了两种基因型根尖的苹果酸释放。然而，耐铝基因型的分泌率显著更高。仅在耐铝基因型IT89KD - 391中，缺磷在有铝存在的情况下诱导苹果酸分泌增加。根尖的柠檬酸分泌率比苹果酸分泌率低约10倍，并且在两种基因型中主要因缺磷而增加。铝处理进一步增强了磷充足植株的柠檬酸分泌，但对缺磷植株没有影响。耐铝基因型IT89KD - 391的柠檬酸分泌水平始终较高，尤其是在有铝存在的情况下。得出的结论是，耐铝基因型比铝敏感基因型更能适应酸性铝毒和缺磷土壤，因为铝和缺磷联合胁迫更能增强苹果酸和柠檬酸的分泌。
