Earthworms help aerate soil and reduce surface runoff erosion by creating networks of tunnels as they burrow holes in the ground. Worms are also decomposers, producing manure that increases the nutritional content of the soil. Determine how the presence of earthworms in soil can affect plant growth by comparing the germination and growth of philodendron and green bean plants in soil samples that contained earthworms with those without earthworms. Prepare two identical pots each of philodendron and green bean seeds, one with 10 earthworms in it and one without worms. Keep all four plants in an identical environment, watering them daily and giving them adequate sunlight. Measure the plants daily. While the green beans germinate within a week, the philodendron requires 15 to 30 days to germinate.
Earthworms do not have senses but they do have nerves that help them sense changes in their environment. Test whether worms react to different odors in the air by placing a cotton ball soaked with different scents near an earthworm in an aquarium. One at a time, place several odors, such as vinegar, orange juice, milk with sugar, water with salt, cleaning solutions and lemon juice, the same distance from the earthworm. Record whether the worm moves closer or further away from the scent or stays still.
Plants use water to make food and stay alive, but they lose water to the air through tiny holes in their leaves called stomates. Discover how much water plants lose through transpiration by conducting an experiment. Plant philodendron and spider plants in small plastic pots and then water the plants until water runs out through the hole in the bottom of the pot. After the water stops running from the pots, dry the outside of the pots and then weigh each one. Place a plastic bag over the top of each plant. Put the plants in a sunny spot for at least an hour and then remove the bags from the pots and weigh them again. Calculate the water lost from the plant as the difference between the original wet weight and the weight after time in the sun. Recover the plants and continue weighing them for several hours.
Determine whether acid rain affects plant growth by placing plant cuttings in acid and distilled water. To create acid water, add vinegar to distilled water until it has a pH level of 4. Measure the pH level using pH paper or a garden soil pH testing kit to ensure the distilled water is not too acidic. If the pH level is below 7, add baking soda or ammonia until the level is 4. Label two jars each of one cup of acid and distilled water and put begonia and philodendron cuttings into the jars, covering the stem and part of the leaf with the liquid. After 7 and 14 days, compare the new root growth in the plants and record your results.