Q.Differentiate cytokinesis in plant cells and animal cells.

Because plant cells have a rigid cell wall, they cannot pinch inward like animal cells; instead they build a new dividing wall (cell plate) from the middle outward, while animal cells constrict inward using a contractile ring.

Cytokinesis is the division of the cytoplasm following mitosis (or meiosis), physically separating the two daughter nuclei into two separate daughter cells. The mechanism differs between plant and animal cells because of their different cell coverings:

Plant cells (cell plate method):

• Because a rigid cellulose cell wall surrounds the cell, the plasma membrane cannot simply pinch inward.
• Instead, Golgi-derived vesicles containing cell-wall building materials accumulate at the equatorial plane (where the spindle fibres/phragmoplast form).
• These vesicles fuse to build a growing partition called the cell plate, which begins at the CENTRE of the cell and grows outward (centrifugally) until it reaches and fuses with the existing lateral cell wall, forming two separate cells, each now with its own new cell wall.
• No cleavage furrow is formed.

Animal cells (cleavage furrow method):

• Animal cells lack a rigid cell wall, so the flexible plasma membrane itself can be drawn inward.
• A ring of actin and myosin filaments (the contractile ring) assembles just beneath the plasma membrane at the cell's equator. …