Within plant seed life cycles, seeds reside in a state of dormancy prior to germination stages. Little activity occurs during dormancy periods as seeds wait for the right environmental conditions for growth to begin. Once germination starts, cellular respiration rates increase dramatically in order to provide needed materials for initial plant growth stages.
Cellular Respiration Functions
Cellular respiration processes provide a means for cells to convert existing nutrient materials into energy. During dormancy periods, plant seeds respire just enough to maintain food, or nutrient supplies within a specialized seed layer known as the endosperm. Within flowering plants, endosperm structures are the product of a double fertilization process that takes place when a plant ovule, or ovary, is first fertilized. In effect, the endosperm provides for the seed's nutrient needs and carries out necessary cellular respiration functions throughout the dormancy period. The start of germination places substantial energy demands on the seed as plant growth processes take shape. As a result, cellular respiration rates increase to accommodate the cell-building activities required to break open the seed and produce the initial root and stem structures.
Cellular Respiration Triggers
Plant seeds originate from flowers, fruits, green plants and trees that grow within a myriad of environmental conditions. Not surprisingly, each seed type seeks out certain environmental triggers that prompt the start of germination processes. According to Cornell University, environmental triggers may appear as increased levels of nutrients in the soil, changes in soil temperature, increased rainfall amounts or increases in the amount and quality of light. Once the needed conditions are met, seeds begin to increase their water-absorption rates, which marks the start of germination. Increases in water absorption enable seeds to mobilize food reserves stored within endosperm layers. These processes activate certain enzymes that trigger increases in a seed's cellular respiration rates.
Cellular Respiration Process
Germinating seeds carry out cellular respiration processes in much the same way as plant and animal cells do. Cellular respiration takes place in three stages starting with glycolysis. The glycolysis stage uses glucose molecules to produce two units of energy or ATP (adenosine triphosphate) molecules along with other chemical materials. The Krebs Cycle makes up the second stage of cellular respiration. This stage uses the products from glycolysis to produce two more energy units and transforms the chemicals left over from glycolysis into hydrogen-carrying molecules. The Electron Transport Chain is the third stage in the respiration process and is fueled by the two ATP molecules produced in the Krebs Cycle. This stage combines the energy contained inside the hydrogen molecules from the Krebs Cycle with oxygen to create 38 ATP molecules. This three-stage process repeats over and over again within each individual plant cell. The ATP molecules produced by cellular respiration provide the energy for seed germination to begin and fuels the cell-building activities that ultimately form the plant body.