Fig. 1. Water stress protocol, using null balance lysimetry. Relative soil water content (RSWC) vs. time is shown for one drought pot and one control pot in a single replication. After reaching their new target weights on each day of the experiment, drought pots were maintained within ± 3% RSWC of the target weight by frequent water additions. Control pots were maintained between 77 and 83% RSWC at all times. The first 24 h of data were used to normalize subsequent days' water use, to account for differences in plant size.