From Seed to Seed:
Plant Science for K-8 Educators

Adaptations for light. Most leaves are sensitive to changes in light levels. If you take a plant that has been growing in the shade and place it in bright sunlight, it can get "sunburned." This is because plants growing in direct sun are smaller and develop a tougher epidermal layer, whereas plants growing in the shade need to optimize their ability to take in sunlight, and are, therefore, larger and have a thinner epidermis. These factors make them less well suited for situations with high light intensity.

Some plants adapt to different light levels by modifying their new growth to suit the new environment. A plant may alter its leaf size and even color depending on light intensity and duration. For example, the common philodendron houseplant tends to produce smaller leaves on longer vines in dim light and larger leaves on shorter vines in bright light. On the other hand, a ficus tree brought from direct sun into dim light will shed some of its old leaves and begin to produce slightly larger, thinner leaves. Many variegated plants, such as crotons and coleus, will have more variegation in brighter light. Test any one of these three scenarios with your students! In most cases, the existing leaves don't change-only the new growth reflects the adaptations to the new conditions.