Abstract
Light microscopic observation indicated that some cells with extremely thin cytoplasm and/or some dark-stained cells emerged among the subunits of actively growing friable callus clumps. After these cells degenerated, a clump would fragment into many small ones. Ultrastructural observation and TUNEL (transferase-mediated dUTP nick-end labeling) assay have revealed that degenerated cells in friable callus derived from immature embryos of Larix gmelini (Rupr.) Rupr. underwent programmed cell death (PCD) during callus fragmentation. There were two types of PCD in the cells of calli. In the first type, PCD was carried out through an in situ autolysis of their cytoplasm. Distinct signs were the partial to complete disappearance of the tonoplast and the sharp decrease of free ribosomes. In the second type, a distinct sign was that the rough endoplasmic reticulum cisternae largely proliferated and dilated to engulf and digest the cytoplasmic components. The organization of the friable callus clumps and the behav...
Published Version
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