Question

If the stem grows toward sunlight and root grows just opposite to it, the stem movement is called as
A. Negative phototropic movement
B. Phototropic movement
C. Positive phototropic movement
D. None of the above

Answer 1

Hint: Movement of the stem can be towards the sunlight or it can be away from the sunlight too and this is the determining factor of positive or negative phototropic movement.

Complete answer: If we look at options A i.e., Negative phototropic movement. Negative phototropic movement is the movement of roots away from light inside the soil and here the growth of the root is negatively phototropic. But in the questions that stem movement is asked where stem grows towards sunlight and root grows opposite of it which is not the case in negative phototropic movement. Thus, this option gets eliminated.
Moving to option B i.e., Phototropic movement. Phototropic movement is the growth of an organism in response to the light and the growth can be towards the sunlight or away from the sunlight. But in the questions that stem movement is asked where stem grows towards sunlight and root grows opposite of it which is the case of positive phototropic movement and it is a part of phototropic movement but not particularly that which has been asked in the question. Thus, this option gets eliminated.
Moving to option C i.e., Positive phototropic movement. Positive phototropic movement is the movement of a stem which grows towards the sunlight and root grows just opposite to it and that is why it is called as positive phototropic movement. This option is therefore the correct one as in the questions also that movement is asked where the stem grows toward sunlight and the root grows just opposite to it.
Last option D is None of the above. This option is incorrect as from all the given options, option C i.e., Positive phototropic movement is the correct option for the asked question.
Thus, the correct answer is option C i.e., Positive phototropic movement.

Note:
Since phototropic movement is of two types i.e., positive phototropic movement and negative phototropic movement. When the stem grows towards the light then it is called positive phototropic movement and when it grows away from the sunlight then it is referred to as negative phototropic movement. Therefore according to the questions, the correct answer is positive phototropic movement.