Net Primary Productivity of Grass
As a plant grows and performs photosynthesis, it does not retain all of the energy that it takes in. Rather, some energy is expended through metabolic processes and is lost as heat. We can measure and calculate these values by observing and comparing the growth of potted grass in dark and light conditions.
Each group will grow three pots of grass. They will weigh the increase in mass of the first pot after a week. The second is left in light, while the third is kept in darkness. The change in mass of the grass in light represents net primary productivity (NPP), while the change in mass of the grass in darkness represents respiration (R). Students can then calculate gross primary productivity (GPP) using those two values.
Materials Required: Square plastic plant pots (3 per group), fast-growing grass seed, peat bricks, grow lights
