Cellular respiration is the consumption of oxygen by a cell within a living organism. In plant seeds, the cellular respiration does not occur until the seed has absorbed moisture and released stored starches that can then be metabolized into energy for the purpose of growth.
Cellular respiration exists in both animal and plant cells. In plant cells, it occurs after germination begins. Plant seeds generally dry out prior to germination. Once they are exposed to moisture, the seeds swell. This moisture triggers the enzyme activity within the cells. Prior to this activity, the metabolic activity within the seeds is very slow. When the enzyme activity begins, the seeds release the nutrients stored within them. Usually starch, these nutrients are metabolized by the enzymes so they can fuel the germination and eventual growth process. The production of this energy allows cellular respiration to begin.
Rate of respiration in germinating seeds can be measured using a respirometer experiment. In this type of experiment, three test tubes are used. One is filled with dry seeds and plastic beads, one is filled with soaked, germinating seeds, and one is filled with enough plastic beads to create equal volume to the other tubes. Plugged with cotton, these tubes are inverted into water. As the seeds consume oxygen, the pressure within each tube decreases, allowing the water to flow in through the cotton. This provides a visual demonstration of how much oxygen is being consumed by the seeds.