Root Growth Stops When Apical Meristem is Removed

The primary reason onion root growth stops after its tip is cut is the removal of the crucial structure responsible for elongation.

• The apical meristem is located at the very tip of the root. It is a region of actively dividing cells (meristematic cells) responsible for the primary growth, or lengthening, of the root.
• When the root tip is cut off, the apical meristem is physically removed.
• Without the apical meristem, there are no longer actively dividing cells producing new cells to extend the root length. Consequently, the root's growth in length ceases.

The other options are less direct causes: meristematic cells require vacuoles for normal function, lateral meristems contribute to thickening (secondary growth) rather than primary elongation, and while other meristems exist, the apical meristem is the primary driver of root tip extension.