A field of sunflowers facing the sun is an example of

Phototropism

Explanation:

Phototropism. Although both types of movement orient plants toward a light source, heliotropism is not the same as phototropism. Phototropism is the term that describes the growth of a plant toward any light source.

Phototropism. Although both types of movement orient plants toward a light source, heliotropism is not the same as phototropism. Phototropism is the term that describes the growth of a plant toward any light source.

Explanation:

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Continuously facing towards the east also helps the flowers to heat up quickly. This gives them an advantage in pollination, as warm flowers attract insects. Therefore, in the plant's interest, the flower always faces the sun and is therefore always clearly visible to these important pollinators.