Question

select the text from the paragraph that best helps you understand that tropism means directional movement of an organism in response to an external stimulus. there may be more than one correct choice.

auxins are plant hormones that promote cell growth and elongation, and they are also among the principal hormones responsible for plant tropism. for example, auxins in plant cells cause plant shoots to grow towards sunlight. they do so, according to one theory, because sunlight degrades the hormones, leading to a higher concentration of auxins on the shade - facing side of the plant. as a result, that side grows more quickly, thus bending the stalk towards the sun. ironically, while these hormones are produced by plants, they can also be used to make herbicides because some plants are sensitive to high auxin levels.

Explanation:

The text "auxins in plant cells cause plant shoots to grow towards sunlight" and "that side grows more quickly, thus bending the stalk towards the sun" shows a directional movement (towards sunlight) of a plant (the shoot/stalk) in response to an external stimulus (sunlight), which aligns with the definition of tropism as directional movement in response to an external stimulus.

Answer:

"auxins in plant cells cause plant shoots to grow towards sunlight" and "that side grows more quickly, thus bending the stalk towards the sun"