Cells. when the cells die they fall off the tree.
I want to say that it would be the 'atomic radius' that would increase. Because as this would happen, the atoms would then get smaller and smaller, mainly because the radius would just get smaller and also the atoms would also.
Plant cells have what is perhaps the most complex outer coverings. Plant cell walls are made largely of cellulose which forms strong, highly rigid, almost indigestible coverings that protect the cell and gives it shape.
The movement of the arms and legs is accomplished by the SOMATIC subdivision of the peripheral nervous system.
The peripheral nervous system is divided into two, they are autonomic nervous system and the somatic nervous system. The somatic nervous system controls the movement of arm and legs.<span />