Lesson 6 of 13 · 5 min
Cytokinesis
NCERT §10.2.5
Ishaan notices that in plant cells on his slide the division line looks like a straight wall growing across, not a pinch. Diya says the wall is the reason.
The lesson in notes
In short
Karyokinesis separates the duplicated chromosomes into two nuclei; cytokinesis then divides the cytoplasm, and with it the cell division is complete.
In an animal cell a furrow appears in the plasma membrane. It deepens steadily until its edges meet in the centre, cutting the cytoplasm in two.
A plant cell sits inside a cell wall that hardly stretches, so it divides another way: the new wall is laid down first at the middle of the cell and spreads outwards until it reaches the old side walls.
The new plant wall starts as a simple precursor, the cell plate, which becomes the middle lamella between the walls of the two neighbouring cells.
While the cytoplasm divides, organelles such as mitochondria and plastids are shared between the two daughter cells.
Sometimes the nucleus divides but the cytoplasm does not. The result is a cell with many nuclei, a syncytium; the liquid endosperm of coconut is NCERT's example.