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Question Video: Identifying the Functions of Auxins in Plants Biology

Which of the following is a correct function of auxins in a plant? [A] Inhibiting plant growth in summer months [B] Increasing the lignification of plant cells [C] Preventing pathogen entry [D] Stimulation of cell elongation in the stem

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Video Transcript

Which of the following is a correct function of auxins in a plant? (A) Inhibiting plant growth in summer months, (B) increasing the lignification of plant cells, (C) preventing pathogen entry, or (D) stimulation of cell elongation in the stem.

Auxins are a group of chemical messengers called hormones that have many different functions. To answer this question, we need to investigate some of the key functions of auxins in plants, so let’s dive right in.

Auxins are produced in the tips of plant roots and stems and can diffuse throughout the rest of the plant from cell to cell to cause their various effects. For example, auxins produced in the cells at the tip of the stem diffuse downward to the cells below. A high concentration of auxins in these cells triggers a series of events that stimulates cell elongation, and therefore the growth of the stem.

If a light source arrives from directly above the stem, auxins diffuse down the stem equally and results in symmetrical cell elongation on all sides of the stem. This causes the stem to grow directly upward toward the light source coming from above. If the light source arrives from one side, auxins accumulate in the cells on the shaded side of the stem, causing these cells to elongate comparatively more than those on the illuminated side. This asymmetrical cell elongation causes the stem to bend in the direction of light.

The directional growth movement of the stem in response to light is called phototropism. Phototropism helps to expose the plants photosynthesizing cells, the majority of which are found in the stem and any leaves that might be attached to it, to more light so that they can carry out photosynthesis more efficiently to produce their own food. We’ve found the correct answer to this question, (D). A function of auxins in a plant is stimulation of cell elongation in the stem.

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