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Question Video: Understanding Movement in Plants Biology

Which of the following statements about plants is correct? [A] Plants are fully immobile organisms, and their direction of growth cannot be changed. [B] Plants have no form of sleep-wake cycle to respond to dark-light cycles. [C] Plants can respond to stimuli, like light and touch, by moving. [D] Plants communicate between their own structures using a central nervous system.

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Video Transcript

Which of the following statements about plants is correct? Plants are fully immobile organisms, and their direction of growth cannot be changed. Plants have no form of sleep-wake cycle to respond to dark-light cycles. Plants can respond to stimuli like light and touch by moving. Or plants communicate between their own structures using a central nervous system.

All living organisms are capable of moving and reacting to changes in their internal and external environment. These changes are called stimuli. Plants are capable of movement in response to several different types of stimuli, like light intensity, touch, heat, and gravity. Some plants are incredibly sensitive to touch, and they can move in response to a touch stimulus via a process called thigmotropism. For example, when the roots of some legumes encounter underground rocks in the soil, they are stimulated to change the direction of their growth away from that obstruction.

Some plants, including legumes, have photoreceptors that can sense changes in light intensity. During the day, their leaves are open and upright, but as night approaches and light intensity falls, their leaves may close up and their stems may droop. When light intensity increases again as daylight approaches, their leaves will return to their normal upright position through a sleep-wake cycle sometimes called nyctinasty.

Let’s look at the different statements given in the question. The first statement says that plants are fully immobile and their direction of growth cannot be changed. This is incorrect, as we’ve already seen two of the many examples of how plants can move. The second statement says that plants have no form of sleep-wake cycle to respond to dark–light cycles. However, as we know, light is one of the stimuli that plants can respond to, so this is incorrect too.

The third option says that plants can respond to stimuli like light and touch by moving. This statement is correct; plants are capable of responding to stimuli or changes in their environment by moving. Let’s just check that the final option is incorrect before we confirm our answer. The fourth option says that plants communicate using a central nervous system. Plants generally communicate between different plant organs through electrical signals and chemicals like plant hormones, but they do not have a central nervous system. So we can confirm that this option is incorrect.

Therefore, the accurate statement is that plants can respond to stimuli like light and touch by moving.

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