LIFE PROCESSES
Fig. 6.11 Sensitive Plant (Touch-me-not plant)
tissue in plants for transmitting the information. Plant cells change the shape When we touch the leaves of Touch– by changing the amount of water in them me–not plant, they begin to fold up and droop. resulting in swelling or shrinking and therefore the leaves in touch-me-not plant When a seed germinates, the roots go shrinks. down , the stem comes up above the soil. So, how do they respond to stimuli?
What happens during the above actions?
Movement dependent on growth:
In the first instance, the leaves of sensitive plants show two different types of movements.
More commonly, the plants respond to stimuli slowly by growing in a particular direction. Because this growth is directional, it appears as if the plant is moving.
1. Movement independent of growth
Let us understand this type of movement with the help of some examples.
Movement- Independent of growth Immediate response to stimulus This movement is sensitive to plant. Here, no growth is involved but, the plant actually moves its leaves in response to touch. But there is neither nervous tissue nor muscle tissue. How does the plant detect the touch and how do the leaves move in response? In touch-me-not plant, if we touch at one point, all the leaflets show the folding movements. This indicates that the stimulus at one point is communicated. But unlike in animal, there is no specialized
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1. Response of the plant to the direction of light (Phototropism) 2. Response of the plant to the direction of gravitational force (Geotropism)
ACTIVITY 6.7 1. Go to the field and find the touch-me-not plant. 2. Touch the plant at one point. 3. Observe what happens.
CHAPTER 6
2. Movement dependent growth