铝胁迫诱导柱花草根系分泌柠檬酸

【目的】为揭示柱花草的耐铝机制,对铝诱导根系分泌柠檬酸进行了研究。【方法】采用水培方法,研究柱花草的耐铝性及铝对柱花草分泌柠檬酸的影响,并与紫花苜蓿进行对比。【结果】10μmol·L-1AlCl3对柱花草幼根生长的抑制不显著,而3和5μmol·L-1AlCl3处理24h后,紫花苜蓿幼根伸长明显受阻、根尖的铬天青着色明显。铝胁迫下柱花草根系分泌柠檬酸,且与铝浓度(10、20、30μmol·L-1AlCl3)和处理时间(6、12、18、24h)呈正相关,而紫花苜蓿根系无明显分泌。10μmol·L-1阴离子通道抑制剂(苯甲酰甲醛、尼氟灭酸、4,4-二异硫氰2,2-二磺酸、蒽9羧酸)显著抑制铝诱导的柱花草根系分泌柠檬酸。然而,铝处理对柱花草根尖柠檬酸合酶活性的影响不显著,蒽9羧酸处理也不改变该酶活性。【结论】根系分泌柠檬酸是柱花草抵御铝毒害的可能机制,而阴离子通道介导此分泌过程。

Al Stress-Induced Citrate Secretion from Roots in Stylosanthes

Objective]To reveal the mechanism responsible for Al-resistance in stylo(Stylosanthes),Al-induced secretion of citrate from roots was investigated.Method]The Al-resistance and the effect of Al on the secretion of citrate from roots in stylo (cv.Reyan 2)with comparison to alfalfa(Medicago sativa L.,cv.Sunshine 3)were studied by hydroponics.Result]There was no dramatic inhibition on the root elongation of stylo exposed to a 10 μmol·L~(-1) AlCl_3 solution,while root elongation was inhibited significantly and the root apices were strongly stained by cyanine R in alfalfa after exposure of roots to 3 or 5μmol·L~(-1) AlCl_3 for 24h.Under Al stress,citrate was secreted from roots of stylo.The amount of citrate secretion in stylo was increased with the increasing Al concentration(10,20,30 μmol·L~(-1) AlCl_3)and the duration of Al treatment(6,12,18,24h),but citrate was not secreted from roots in alfalfa.On the other hand,10 μmol·L~(-1) anion channel inhibitors including phenylglyoxal,niflumic acid,4,4'-disothiocyanastilbene-2,2'-disulfonic acid,and 9-anthracenecarboxylic acid blocked the secretion in stylo.However,neither Al treatment nor the treatment with A-9-C failed to affect the citrate synthase activity of the root apices significantly in stylo.Conclusion]These results suggest that Al-induced secretion of citrate from roots may be amechanism responsible for Al-resistance and the anion channels involve in the secretion in the stylo.