Aluminum-induced cell death in root-tip cells of barley

Aluminum-induced cell death was investigated in root-tip cells of barley (H ordeum vulgare). The growth of roots in 0.1-50 mM Al treatments was inhibit ed after 8 h treatments, and could not be recovered after 24 h recovery cul ture without Al. Viable detection with fluorescein diacetate-propidium iodi de (FDA-PI) staining shows that most of the root-tip cells have lost viabil ity. These results suggest that the irreversible inhibition of root growth after 8 h Al treatments or 24 h recovery culture is mainly caused by cell d eath. DNA ladders occurred in root tips only after 8 h Al treatments (0.1-1 .0 mM), but no apoptotic bodies in root tips were observed. Thus, the cell death caused by Al stress is likely to be Al-induced programmed cell death (PCD). The reactive oxygen species (ROS) in root-tip cells measured by ultr aweak luminescence indicated that the oxidation status in root-tip cells ba sically ceased after exposure to 10-50 mM Al for 24 h, but was very violent in the root-tip cells treated with 0.1-1.0 mM for 24 h. Exposure to 0.1-1. 0 mM Al for 3-12 h led to ROS burst. Therefore, our results suggest that 0. 1-1.0 mM Al treatments for 8 h induce cell death (Al-induced PCD) possibly via a ROS-activated signal transduction pathway, whereas 10-50 mM Al treatm ents may cause necrosis in the root-tip cells. These results have an import ant role for further studies on the mechanism of Al toxicity in plants. (C) 2001 Elsevier Science B.V. All rights reserved.