phase, DNA replication begins in the nucleus, and the centriole duplicates in the cytoplasm. During the G phase, proteins are synthesised in preparation for mitosis while cell growth continues. How do plants and animals continue to grow all their lives? Do all cells in a plant divide all the time?
Do you think all cells continue to divide in all plants and animals? Can you tell the name and the location of tissues having cells that divide all their life in higher plants? Do animals have similar m e r i s t e m a t i c tissues? Figure .
A diagrammatic view of cell cycle indicating formation of two cells from one cell M Phase Some cells in the adult animals do not appear to exhibit division (e.g., heart cells) and many other cells divide only occasionally, as needed to replace cells that have been lost because of injury or cell death. These cells that do not divide further exit G phase to enter an inactive stage called quiescent stage (G quiescent stage (G quiescent stage (G quiescent stage (G quiescent stage (G 00000 ))))) of the cell cycle. Cells in this stage remain metabolically active but no longer proliferate unless called on to do so depending on the requirement of the organism. In animals, mitotic cell division is only seen in the diploid somatic cells.
However, there are few exceptions to this where haploid cells divide by mitosis, for example, male honey bees. Against this, the plants can show mitotic divisions in both haploid and diploid cells. From your recollection of examples of alternation of generations in plants (Chapter ) identify plant species and stages at which mitosis is seen in haploid cells.