Ask students what they think a seed needs to sprout and you may get a variety of responses. In the February 2006 edition of The American Biology Teacher, researchers interviewed K-8 students, asking them to identify plants (interview items included: grass, trees, mushrooms, ferns, bread mold, telephone pole, walking stick insect, seeds, bushes, flowers, and a Venus flytrap) and items needed for plants to grow (sun, lightbulb, water, cereal, bee, plant food, worm, air, oxygen, carbon dioxide, sandwich, and potting soil). Many students classified flowers as plants but not trees, stating that trees form their own group. Most students, regardless of age stated that plants needed sun, water, air, and soil for growth. They were less certain of whether or not plants needed oxygen or carbon dioxide to grow.
"Inquiry with Seeds: To Meet the Science Education Standards" by Krantz and Barrow, in the same issue, focused on pre-service teachers and their experiences in a semester long course in learning to teach science through inquiry. The pre-service teachers developed a lesson plan to study seed sprouting requirements.
Currently, I am enrolled in a graduate course focusing on teaching science through inquiry. My classmates and I are also studying the requirements for seed sprouting. These photos show my samples for germinating seeds without soil and controlling the variable of light. By using the clear plastic cups, students can observe the seed's activity as it sprouts. They also have the advantage of seeing the root structures, something you cannot observe when seeds are planted in soil.