ICSE Class 10 Biology
Question 2 of 10
Chemical Coordination in Plants — Question 3
Back to all questions(a) Difference between thigmotropism and geotropism
| Thigmotropism | Geotropism |
|---|---|
| Directional growth movement of a plant part in response to the touch of an object. | Directional growth movement of a plant part in response to gravity. |
| Example — Plants such as sweet peas, Cuscuta and vines have tendrils which coil around other plants in response to one sided contact or touch. | Example — Growth of roots of plants in downward direction. |
(b) Difference between positive and negative tropism
| Positive tropism | Negative tropism |
|---|---|
| Movement of plant part towards the direction of the stimulus is called positive tropism. | Movement of plant part against the direction of the stimulus is called negative tropism. |
| Example — Shoots show positive phototropism and grow in the direction of sunlight. | Example — Roots show negative phototropism and grow against the direction of sunlight. |
(c) Difference between stimulus and response
| Stimulus | Response |
|---|---|
| Change in the internal or external environment of an organism is called a stimulus. | Resulting action or movement caused by the stimulus is called a response. |
| Example — In phototropism, sunlight is the stimulus. | Example — In phototropism, the bending of the shoot is the response to the stimulus of sunlight. |
(d) Difference between phototropism and chemotropism
| Phototropism | Chemotropism |
|---|---|
| It means the movement in response to the stimulus of light. | It is the phenomenon of growth or movement of a plant part towards the source of nutrients or chemicals. |
| Example — Growth of shoots of plants in upward direction. | Example — Growth of pollen tube towards sugar and peptones of the female gametophyte. |