A bean in light, a bean in dark
Green leaves make food by photosynthesis, and they need light for it. A bean seed can sprout in the dark because it has stored food. But in the dark the young plant cannot make any more. It stretches tall and thin and stays pale, as if it were searching for light. The plant in the light grows sturdy stems and green leaves. To compare them fairly we use two cups with the same soil, the same seeds and the same water, and the same warmth. We change only the light. Then we record data for several days: height and colour. Notice that the pale plant can be taller, but taller is not the same as healthy.
| Day | Cup A (light) | Cup B (dark) |
|---|---|---|
| 3 | 2 cm, green | 3 cm, pale |
| 6 | 5 cm, green | 8 cm, pale and thin |
| 9 | 9 cm, green | 13 cm, pale and thin |
Light and dark test (about 9 days, a grown-up helps). Plant one bean seed in each of two cups of soil, 2 cm deep, and give both the same small amount of water. Put cup A on a bright windowsill and cup B in a closed cardboard box in the same room, not in a hot place. Predict first. Every two days take both out for a minute and write the height and colour in a table. Water both equally. Wash your hands afterwards.
| Day | Light (cm) | Dark (cm) |
|---|---|---|
| 6 | 5 | 8 |