Is the mRNA produced constant during time?

I am doing a statistical data analysis of a dataset of P. Furiosus cells exposed to gamma radiation.

For the samples exposed to gamma radiation, I have the values of mRNA produced over time. For the samples not exposed to gamma radiation (reference samples), I do not have the time at which the mRNA has been extracted.

Therefore, I was wondering: under normal conditions, generally, is the mRNA produced constant with respect to time? I thought that maybe the fact that is constant could be the reason for which there are not the values of time.