However, as a complicating factor, the degree of fractionation (i.e. change in isotope ratio) occurring due to photosynthesis is not entirely dependent on the water drawn up by the plant, as fractionation can occur as a result of preferential evaporation of  and other small but significant processes.
However, another complicating aspect is that the degree of fractionation (change in isotope ratio) caused by photosynthesis isn't entirely dependent on the water drawn up by the plant; other preferential evaporation and small-scale processes can also lead to this change.