He Cj., Finlayson S. A., Drew M. C., Jordan W. R., Morgan P. W.
Department of Horticultural Sciences (C.-j.H., M.C.D.) and Department of Soil and Crop Sciences (S.A.F., W.R.J., P.W.M.), Texas A&M University, College Station, Texas 77843.
Plant Physiol. 1996 Dec;112(4):1679-1685. doi: 10.1104/pp.112.4.1679.
Germinated maize (Zea mays L.) seedlings were enclosed in modified triaxial cells in an artificial substrate and exposed to oxygen deficiency stress (4% oxygen, hypoxia) or to mechanical resistance to elongation growth (mechanical impedance) achieved by external pressure on the artificial substrate, or to both hypoxia and impedance simultaneously. Compared with controls, seedlings that received either hypoxia or mechanical impedance exhibited increased rates of ethylene evolution, greater activities of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase, ACC oxidase, and cellulase, and more cell death and aerenchyma formation in the root cortex. Effects of hypoxia plus mechanical impedance were strongly synergistic on ethylene evolution and ACC synthase activity; cellulase activity, ACC oxidase activity, or aerenchyma formation did not exhibit this synergism. In addition, the lag between the onset of stress and increases in both ACC synthase activity and ethylene production was shortened by 2 to 3 h when mechanical impedance or impedance plus hypoxia was applied compared with hypoxia alone. The synergistic effects of hypoxia and mechanical impedance and the earlier responses to mechanical impedance than to hypoxia suggest that different mechanisms are involved in the promotive effects of these stresses on maize root ethylene biosynthesis.
将发芽的玉米（Zea mays L.）幼苗置于人工基质中的改良三轴细胞中，使其遭受缺氧胁迫（4%氧气，低氧），或通过对人工基质施加外部压力实现对伸长生长的机械阻力（机械阻抗），或同时遭受低氧和阻抗。与对照相比，遭受低氧或机械阻抗的幼苗乙烯释放速率增加，1-氨基环丙烷-1-羧酸（ACC）合酶、ACC氧化酶和纤维素酶的活性更高，根皮层中的细胞死亡和气腔形成更多。低氧加机械阻抗对乙烯释放和ACC合酶活性具有强烈的协同作用；纤维素酶活性、ACC氧化酶活性或气腔形成未表现出这种协同作用。此外，与单独低氧相比，施加机械阻抗或阻抗加低氧时，胁迫开始与ACC合酶活性和乙烯产生增加之间的延迟缩短了2至3小时。低氧和机械阻抗的协同作用以及对机械阻抗的反应早于对低氧的反应表明，这些胁迫对玉米根乙烯生物合成的促进作用涉及不同的机制。
