Groppa María D, Zawoznik Myriam S, Tomaro María L, Benavides María P
Departamento de Química Biológica, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, 1113 Buenos Aires, Argentina.
Biol Trace Elem Res. 2008 Winter;126(1-3):246-56. doi: 10.1007/s12011-008-8191-y. Epub 2008 Aug 6.
Although sunflower is usually regarded as a highly tolerant crop, impairment of root growth at initial stages of plant development may result in poor crop establishment and higher susceptibility to pathogen attack. In order to evaluate if Cd2+ and Cu2+ may impact on sunflower germination and initial root development, a pot experiment under controlled conditions was carried out. Possible involvement of polyamine metabolism in sunflower response to these stressors was also investigated. Although Cd2+ and Cu2+ treatments affect neither seed germination nor radical emergence, sunflower seedlings grown in the presence of these heavy metals showed significant inhibition of root growth, being this inhibition greater for Cd2+. Both metals caused significant increases in proline contents at the highest concentrations tested (0.5 and 1 mM), and these increments were more pronounced for Cd2+ treatments, especially between days 3 and 10. Metals also increased putrescine (Put) contents at all concentrations assayed from the seventh day onward, causing no variations on this polyamine time-course pattern. Spermine and spermidine contents, however, were increased only by 1 mM Cd2+. Arginine decarboxylase seems to have been the enzyme responsible for Put increases under both metal treatments. This work demonstrates that initial root growth of sunflower seedlings may be significantly impaired in Cd2+ or Cu2+ contaminated soils. It also shows that polyamines are key biological compounds, which are probably involved in signaling pathways triggered under stress environmental conditions.
尽管向日葵通常被视为一种耐受性很强的作物，但在植物发育初期根系生长受到损害可能会导致作物定植不良，并更容易受到病原体攻击。为了评估镉离子（Cd2+）和铜离子（Cu2+）是否会影响向日葵的发芽和初期根系发育，在可控条件下进行了盆栽试验。同时还研究了多胺代谢在向日葵对这些应激源反应中的可能作用。尽管镉离子和铜离子处理既不影响种子发芽也不影响胚根出现，但在这些重金属存在的情况下生长的向日葵幼苗根系生长受到显著抑制，镉离子处理的抑制作用更强。在测试的最高浓度（0.5和1 mM）下，两种金属均导致脯氨酸含量显著增加，镉离子处理的增幅更为明显，尤其是在第3天至第10天之间。从第7天起，在所有测定浓度下，金属也增加了腐胺（Put）的含量，且未改变该多胺的时间进程模式。然而，精胺和亚精胺含量仅在1 mM镉离子处理下增加。在两种金属处理下，精氨酸脱羧酶似乎是导致腐胺增加的酶。这项研究表明，在被镉离子或铜离子污染的土壤中，向日葵幼苗的初期根系生长可能会受到显著损害。研究还表明，多胺是关键的生物化合物，可能参与了在应激环境条件下触发的信号通路。
