Show the difference in types of stem growth by comparing the length, diameter and leaf formation of the stems of several different plants of the same age. Climbing plants, such as pole green beans, develop differently from bush type green bean plants. Tomatoes grow differently from cucumbers. Document the differences on a daily basis for a few weeks. Point out the differences between plants that require support and those that support themselves in terms of development. Discuss how the size of each plant's product affects its stem requirements.
Place fine marks with waterproof ink at fixed intervals along the stem of a young plant. Measure the distance between the marks each day. Document the location of growth areas with photographs and statistical tables. Use specimens of different plants to compare the growth patterns of each. As an alternative, use multiple plants of the same kind but vary their growth conditions. Compare how more or less water, direct or indirect sun, or supported versus unsupported plants grow and what makes a difference. Pinch the very top tip of the stem from one of the plants and observe how the absence of the tip changes the growth pattern.
Study the effects of light on stem growth by varying the available light. Prepare several pots with the same type and number of seeds. Place each pot under a separate box. Uncover all of the pots at the same time each day then recover them at varying intervals: the first after two hours, the second after four hours and the third after six hours, for example. Another experiment could involve placing the pots in boxes, with each box having a hole in one side. Position the boxes so that the holes face in different directions. Both experiments provide data to help analyze the phototropism, or light sensitivity, of the plants and how it affects stem growth.
Plant green bean seeds in each of five pots. In the first pot, plant the seeds with the curved side facing up and label the pot as to the seeds' orientation. In the next pot, turn the seeds curved side down and label the pot. Plant and label the remaining pots as curved side to the right, curved side to the left and standing on end, respectively. Provide all pots with the same growing conditions. Observe the stem growth of each pot. Analyze whether the plants show geotropism or sensitivity to orientation.