Plants photosynthesize <em>only in the light but respire in light and dark</em>.
Explanation:
The reactions of photosynthesis occur only during the day. This is because sunlight is used for converting water and carbon dioxide into oxygen and glucose in the presence of sunlight. The light of the sun s the energy force which drives this reaction.
However, the reactions of respiration continue at day and night. The reactions of respiration do not require light energy from the sun.
There are histones in the nucleus that DNA coils around. The part of the DNA that is coiled around the histones is not accessible, and cannot be expressed in that cell. DNA that is not wrapped around a histone can be transcribed.