Grades K–2 · Organisms
Why do some flowers open and close?
Some flowers spread their petals wide and later bring them close together. The petals do not have muscles like your arms. They are made of tiny living parts called cells.
In the diagramPetal tissues can change a flower’s shapePetals spreadPetals closer togetherspreadfolded inwardWater pressure and uneven growth can bend petal tissues.
Water inside a cell pushes against its wall. Changes in that push, or different amounts of growth on the two sides of a petal, can bend the petal. Many small changes together can move a whole flower.
Light, warmth and a plant’s inner daily timing can help control these changes. Different flowers respond in different ways. A flower closing for the evening is still alive and carrying out its own processes.
About this explanation
Starting knowledge: Notice an open flower and a closed flower at different times.
Sources
- Beauzamy, Nakayama and Boudaoud, Annals of Botany — Flowers under pressure: ins and outs of turgor regulation in development