Chemotropism, the growth or movement of plants in response to chemical stimuli, is a fascinating phenomenon that can be easily observed in outdoor plant boxes. Certain plants are particularly effective at showcasing this behavior, making them ideal choices for gardeners and educators alike.

1. Peas (Pisum sativum): Pea plants are classic examples of chemotropism, especially their roots, which grow toward nutrient-rich soil or fertilizers. Their rapid growth and visible root development make them perfect for outdoor plant boxes.

2. Sunflowers (Helianthus annuus): Sunflowers exhibit chemotropism by orienting their roots toward water-soluble nutrients. Their large size and dramatic growth patterns make them a striking choice for demonstrations.

3. Beans (Phaseolus vulgaris): Bean plants respond strongly to nitrogen-rich compounds, showcasing chemotropic root growth. They are hardy and easy to grow in outdoor settings.

4. Marigolds (Tagetes spp.): These flowers are not only colorful but also exhibit chemotropic responses to soil nutrients, making them both functional and decorative in plant boxes.

5. Tomatoes (Solanum lycopersicum): Tomato plants demonstrate chemotropism by growing roots toward nutrient-dense areas, particularly when fertilized. Their vigorous growth is ideal for outdoor experiments.

By selecting these plants, you can create a dynamic outdoor display that highlights the wonders of chemotropism, offering both visual appeal and educational value.