Reluctantly she pulled away, her pulse and respiration in a race.
Terrestrial plants have a gaseous interchange of oxygen and carbon dioxide which is necessary for respiration and feeding.
The important function of aeration, by which the inner living tissues of the bulky plant-body obtain the oxygen necessary for their respiration, is secured by the development of an extensive system of intercellular spaces communicating with the external air.
This tissue is called aerenchym, and no doubt its function is to facilitate the respiration of the organs on which it is formed and to which the access of oxygen is difficult.
The changes involve a continual liberation of energy, which in most cases is caused by the respiration of the protoplasm and the oxidation of the substances it contains.