APOPTOSIS IN PLANTS

Apoptosis is a feature of animal cells that explains some aspects of p rogrammed cell death in plants. Differences between plant and animal c ell development require that concepts be reexamined to signify how pla nt cells have evolved the need for cell elimination in the meristemati c growth habit, life cycle, and alternation of generations. Central to this theme is the regulation of divisional cycles for mitosis, meiosi s, apomeiosis, and their related sexual and asexual reproductive proce sses. Apoptosis depends on the coordinated expression of genes regulat ing divisional cycles and apoptotic pathways so that irreversible nucl ear and cytoplasmic elimination occurs. Cellular degradation products are salvaged to sustain adaptation, viability, structural function, an d ontogeny. The cell wall is usually retained and further differentiat ed or eliminated. A model of factors predisposing apoptosis and compri sing checkpoints in cell divisional cycles is presented for comparison s among plant and animal cells.