An example of a beginner plant science project would be an experiment with colored water and white carnations to examine capillary action. More advanced plant science projects include determining water quality using duckweed and determining the effect that plants have on carbon dioxide levels and temperature.
To do the carnation experiment, several white carnations, water, food dye, and a vase are required. Put an appropriate amount of dye in the vase's water, and then place the carnations into the water stem first. Let the flowers remain in the water, and note the travel of the dye up the stem and into the white petals per hour. Take photographs if necessary. The dye is most noticeable in the flower and bumps where leaves emerge.
To experiment on water quality, gather duckweed from a nearby pond, or buy it from a nursery and grow it in bowls of water in direct sunlight. Use several bowls of different water types, including tap water, bottled water, water with fertilizer and water made acidic with vinegar. Examine each plant's growth at the end of a week visually, or dry the plants and weigh. To test the effect of plants on global warming, make a terrarium in a pickle jar, and place a thermometer in it before sealing. In a separate, empty jar, place another thermometer, and seal the jar. Place both in direct sunlight, and record differences in temperature.