AL-PCD morphology in cell suspension cultures and root hairs of Arabidopsis thaliana. (A), (B) Living cells from a seven day old suspension culture stained with FDA and viewed under white (A) or fluorescent light (B). (C) Two cells from a seven day cell suspension culture 24 hr after a 10 min heat shock at 55°C, showing retraction of the cytoplasm, a characteristic hallmark of AL-PCD. When stained with FDA these cells do not fluoresce indicating that they have undergone cell death. (D), (E) Root hair stained with FDA and viewed under white (D) or fluorescent light (E). Unlike root hairs treated with heat no retraction of the cytoplasm can be observed. (F) Root hair of Arabidopsis thaliana 6 hr after a 10 min heat shock at 55°C. The root hair shows retraction of the cytoplasm and no fluorescence following FDA treatment indicating it has undergone AL-PCD. Scalebars: 40 μm A-C and 10 μm D-F.