Arrangement of leaves on the shoot
Leaves are arranged on a shoot in a definite order. In alternate arrangement one leaf grows from each node (apple, apricot, hawthorn, poplar, mulberry, grape, rose, cotton, tomato). In opposite arrangement two leaves grow opposite each other from one node (basil, mint, carnation, lilac, St John’s wort). In whorled arrangement three or more leaves grow in a ring from one node (oleander, horsetail). However many leaves there are, they are placed so that they shade each other little and catch sunlight: petioles have different lengths and blades turn towards the Sun. This is called leaf mosaic. Thanks to it each leaf gets enough light for photosynthesis.
| Arrangement | At one node | Example |
|---|---|---|
| Alternate | 1 leaf | hawthorn, rose |
| Opposite | 2 leaves, facing each other | mint, carnation |
| Whorled | 3 or more, in a ring | — |
Experiment: put two identical houseplants by a window. Turn one towards the light every day and leave the other alone. After 5–7 days compare the leaf positions and draw them. Extra: identify the leaf arrangement of 5 plants around the classroom and tabulate it. Safety: lift pots with both hands and carefully near the window.