Heim D R, Larrinua I M
Lilly Research Laboratories, A Division of Eli Lilly and Company, P. O. Box 708, Greenfield, Indiana 46140.
Plant Physiol. 1989 Nov;91(3):1226-31. doi: 10.1104/pp.91.3.1226.
Interference with histidine metabolism, inhibition of pigment biosynthesis, or both have been the principal candidates for the primary site of action of 3-amino 1,2,4-triazole (amitrole). Arabidopsis thaliana is sensitive to 1,2,4-triazole-3-alanine, a feedback inhibitor of histidine biosynthesis, and this effect is reversed by histidine. The combination of triazolealanine and histidine, however, does not reverse the herbicidal effect of amitrole. This indicates that amitrole toxicity is not caused by histidine starvation, nor is it caused by the accumulation of a toxic intermediate of the histidine pathway. Amitrole inhibits root elongation at lower concentrations than it causes pigment bleaching in the leaves. In contrast, fluridone, a known inhibitor of the carotenoid biosynthetic pathway does not block root elongation. Fluridone also inhibits carotenoid accumulation in etiolated seedlings in the dark, but amitrole does not. Last, gabaculine and acifluorfen, but not amitrole, prevent chlorophyll accumulation in greening etiolated seedlings of Arabidopsis. These experiments cast doubt on pigment biosynthesis as the primary site of action of amitrole.
干扰组氨酸代谢、抑制色素生物合成或两者兼而有之，一直是3-氨基-1,2,4-三唑（杀草强）主要作用位点的候选因素。拟南芥对组氨酸生物合成的反馈抑制剂1,2,4-三唑-3-丙氨酸敏感，而这种效应可被组氨酸逆转。然而，三唑丙氨酸和组氨酸的组合并不能逆转杀草强的除草效果。这表明杀草强的毒性不是由组氨酸饥饿引起的，也不是由组氨酸途径的有毒中间产物积累所致。杀草强在抑制根系伸长时的浓度低于其导致叶片色素漂白时的浓度。相比之下，类胡萝卜素生物合成途径的已知抑制剂氟啶酮不会阻止根系伸长。氟啶酮还能抑制黑暗中黄化幼苗的类胡萝卜素积累，但杀草强则不能。最后，加巴喷丁和三氟羧草醚能阻止拟南芥黄化幼苗绿化过程中的叶绿素积累，但杀草强不能。这些实验对色素生物合成作为杀草强主要作用位点提出了质疑。
