The response of plants to the relative length of light and darkness is termed

A) phototropism.
B) photosynthesis.
C) photoperiodism.
D) translocation.
E) transpiration.

Photoperiodism refers to the physiological reaction of organisms to the length of day or night, which is particularly important in the time of year when day length changes, such as during the winter and summer solstices. Plants use photoperiodism to regulate their growth and reproductive processes, and it is often used to induce flowering in crops. Phototropism refers to the movement of plants in response to light, while photosynthesis refers to the process by which plants use light energy to produce sugars. Translocation refers to the movement of sugars and other molecules throughout a plant, while transpiration refers to the loss of water through the leaves.