The wind, objects that prevent the tree from growing upwards.
The mangrove trees can have many trunks, but the banyan tree has both multiple trunks and above-ground "prop roots" that can grow vertically and horizontally.
The tree trunks are cylindrical because they grow from the center and outwards. They grow uniformly and this is evident from the rings when the trees are cut.
Tree trunks are straight and branchless in their lower parts in their efforts to grow tall.
Not a plant it can be any tree. And no plants grow on any trunks
Tree trunks are straight and branchless in their lower parts in their efforts to grow tall.
Many plants which are called epiphytes grow on tree trunks. They are adapted to grow there as orchids , lichens etc.
the roots underneath the trunk let the tree grow
Tree trunks is that trees middle position.
tree trunks have xylem and phloem
Some trees are naturally prone to grow that way. For those that should have straight trunks, the tree may have been planted with the trunk crooked or wind may have caused the tree to become crooked. Staking the tree would avoid that. Other causes could be injury or weather.
Trunks
Lichen is a combination of fungus and algae. It grows on tree trunks.