An example of slow, directional growth in plants is demonstrated by sunflowers. Sunflowers track the movement of the sun throughout the day, slowly reorienting their blooms to face the sunlight. This apparent movement is a result of the plant’s growth in response to the stimulus of sunlight.
Provide an example to illustrate how plants exhibit slow, directional growth in response to stimuli.
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Phototropism exemplifies how plants display slow, directional growth in response to stimuli. Consider a potted sunflower seedling placed near a window. Initially straight, the seedling’s stem gradually bends towards the light source. This phenomenon results from differential cell elongation, where cells on the shaded side elongate more rapidly than those exposed to light. The plant hormone auxin plays a pivotal role, redistributing itself in response to light. As light stimulates auxin movement away from the light source, it accumulates on the shaded side, promoting cell elongation and causing the stem to curve. This process unfolds over hours to days, underscoring the deliberate and directional nature of the plant’s growth response to optimize sunlight exposure for photosynthesis.