Growth and water productivity of RCAR6- and RCAR10-overexpressing Arabidopsis under controlled soil water levels. Growth and water productivity of RCAR6- and RCAR10-overexpressing Arabidopsis under controlled soil water levels. Plant growth was assessed by the increase in leaf area at different water regimes with (A) 60% (Ψ = −0.08 MPa), (B) 40% (Ψ = −0.10 MPa), and (C) 20% (Ψ = −0.21 MPa) relative soil water content (v/v, SWC) for the wild-type Col-0 (Col), RCAR6-3 lines (R6), and RCAR10-4 (R10). D, Leaf temperature of plants at day 18. E, Consumed water and final above-ground dry matter. F, Water use efficiency (WUE). Plantlets were grown for 25 d under short-day conditions and pots were allowed to reach the designated SWC by evaporation prior to the onset of the experiment. At this stage, the plants had a leaf area of 1.7 ± 0.1 cm2, 1.8 ± 0.1 cm2, 2.0 ± 0.1 cm2 for Col, R6, and R10, respectively. Water was administrated in intervals of 3 days to adjust the water content to the target SWCs. The lowest SWC values reached during the experiment were approximately 45%, 25%, and 15% SWC for the water regime of 60%, 40%, and 20% SWC, respectively. Mean ±sem; n = 4 biological replicates for each data point; ***P < 0.001 (one-way ANOVA) compared with the wild-type Col-0. Zhenyu Yang et al. Plant Physiol. 2019;180:1066-1080 ©2019 by American Society of Plant Biologists