Why do trees and shrubs growing in deserts have long roots thick barks sharp thorns?

Answer 1

they have long roots in order to reach down as far as possible into the ground to gather whatever nutrients and water there is, they have thick barks to help retain water and they have sharp thorns to reduce surface area, as if there was a large surface area,(like a leaf) more water would be evaporated and the trees in the desert need to hold onto as much water as they can. the sharp thorns could also be a mechanism to deter predators!