Tulip

Tulips (tulipa) are heliotropic: growth hormones on the stem accumulate on its shaded side to accelerate growth, forcing the stem to bend in the direction of light. In response to changes in light and heat, the flower petals expand during the day or contract at night. When open during the day, the tulip optimizes for daytime pollinators. When closed at night, it retains warmth during cool spring nights, preventing dampness and rain from degrading its pollen.