Thanks for taking care of most of the comments of the reviewers. To my point, one (important) comment of reviewer #4 has not been accounted for adequately. I fully agree with the reviewer that AT% is not sufficient for assessing uptake. Apart from the lack of change in biomass (which to my point of view needs to be described clearly in the text and figure caption, as it is critical information for the interpretation of the data), the other variable in between AT% and N-uptake is the total amount of N (mg N/g leaf/root/soil). given differences in total N content in time, between treatments etc., the interpretation may be affected. So, please express all as mg 15N/g d.w.
Also, I found the units of the y-axis of fig 2a difficult to read, please convert to ug cm-2 d-1 or ideally to full SI units.