Relation of evaporation and transpiration to maintain plant production

Andisol in a pot was placed in a controlled air condition room and evaporation rate was measured. After that, another similar pot with leaf plants were placed in the same room but with light condition in daytime to measure evapo-transpiration rate. Analysis of the evaporation rate revealed that the rate was well expressed the simple function of time as ArcSinh[t]. Analysis of the evapo-transpiration showed an almost constant daily pattern during first several days but after that the rate decreased. This decrease was almost proportional to the decrease in soil water content.