Question 10

Turning toward the Sun

Heliotropic refers to the ability of certain plants, like sunflowers, to orient themselves towards the Sun. This phenomenon allows sunflowers to maximize their exposure to sunlight throughout the day.

A) Having a flexible pulvinus

While the pulvinus is indeed a flexible segment of the sunflower's stem that facilitates its movement, the term "heliotropic" does not specifically refer to this structural feature. Instead, it describes the overall behavior of the plant in response to sunlight.

B) Flowering in the bud stage

This option is incorrect as heliotropism is not related to the flowering stage of the sunflower. The term focuses on the movement of the plant in relation to the Sun, rather than its developmental stage.

C) Having brightly-colored flowers

Though sunflowers are known for their vibrant colors, this characteristic does not pertain to heliotropism. The term describes the directional growth or movement towards sunlight, not the coloration of the flowers.

D) Turning toward the Sun

This is the correct interpretation of heliotropism, as it specifically describes the ability of sunflowers to follow the Sun's path across the sky from east to west. This behavior is a crucial adaptation for maximizing photosynthesis.

Conclusion

The correct answer, "turning toward the Sun," accurately captures the essence of heliotropism as demonstrated by sunflowers. All other options fail to address the fundamental concept of directional movement in relation to sunlight, which is the core aspect of heliotropism. Thus, option D is the only choice that aligns with the definition provided in the extract.