The growth of plants stop if its apical part is cut, why？​

On some kinds of plants, the meristem is arranged so that when the tip of a branch or stem - which contains the apical meristem, from which new growth is initiated - is cut off, new stems or branches are signaled to start growing from the side, an area called the cambium or lateral meristem. These kinds of plants don’t die if the tip is cut off - instead they grow new branches.

Explanation:

good luck

The apical bud produces a hormone, auxin, (IAA) that inhibits growth of the lateral buds further down the stem towards the axillary bud... When the apical is removed bud I'd removed, the lowered IAA concentration allow the lateral buds to grow and produce new shoots, which compete to become the lead growth

showing a photograph would make this a hell of alot easier