Question

The height of a plants does not grow when it's too is cut

Answer 1

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.

Answer 2

If an apex of a plant is cut down, it does not grow long,

Because the apex Contains apical buds which help in longitudinal, growth of Plant . If it is cut then length of the plant doesn't increase