How would you explain the significance of transpiration?
The significance is that we would not be alive without it.
Transpiration is the process in plants and trees that get water "from source to sink" (from roots to leaves). This process does not require trees to use energy.
Because of diffusion (the movement of particles from high concentration to low concentration) the water automatically gets sucked up from the roots.
You could say that the leaves "sweat" out water (water evaporates from the cells of the leaf). This causes a low concentration of water in that cell. And so like a chain, as if something was pulling it, the water goes from high concentration (roots), to low (leaf).
Diffusion is strong enough to defy gravity to a certain height (this is why trees can't be taller than they are).
Causes of diffusion is that there is less water outside the leaf than inside, and so the water "evaporates". So the transpiration process is faster if the air is dry, if it is hot, or if there is much wind to blow away the water that has already evaporated.
The higher the temperature, the faster particles diffuse.
So transpiration is essential for the existence of trees and plants, and therefore, also us.