How do trees breathe and why ?

Trees are multicellular, eukaryotic organisms capable of producing glucose by the process of photosynthesis. However, they need to also carry out aerobic respiration in order to obtain energy from the glucose to use for metabolic processes including growth, repair and reproduction. That energy is in the form of adenosine triphosphate also known as ATP.

When we think of breathing in humans, we think of oxygen being inhaled and carbon dioxide and water vapor being exhaled...

Trees are multicellular, eukaryotic organisms capable of producing glucose by the process of photosynthesis. However, they need to also carry out aerobic respiration in order to obtain energy from the glucose to use for metabolic processes including growth, repair and reproduction. That energy is in the form of adenosine triphosphate also known as ATP.

When we think of breathing in humans, we think of oxygen being inhaled and carbon dioxide and water vapor being exhaled which is part of respiration.

The question states..why do trees breathe and the word respiration can be substituted here--why do trees carry out respiration?

Plants take in carbon dioxide through stomata (tiny pores)  in the leaves, and absorb water through their root system. Light is absorbed by leaves and with these three reactants, photosynthesis can proceed.  The products of this reaction are glucose, oxygen and water. Energy originally from the sun was transferred and then transformed into the chemical energy of glucose and glucose can then be used as a reactant during respiration to release ATP.

The oxygen and water vapor that plants "breathe out" are released as waste products to the environment through stomata in their leaves after photosynthesis. However, some of the oxygen can be used during aerobic cellular respiration so that plants can fully oxidize the glucose fuel to release its energy for the plant to use as 32-34 molecules of ATP.

To conclude, plants need to take in and release gases much like any organism that breathes. However, their adaptation to obtain or excrete gases is accomplished by their stomata. Roots hairs can also exchange gases with the environment of the plant.