Fig. 6: PSR plays a crucial role in plant growth under mild drought.

a Schematic overview of the experimental design for control, mild drought, and rehydration treatment in Arabidopsis plants. Pots containing 14-day-old plants soaked in water with liquid nutrients after transplanting 7-day-old plants from agar plates were soaked in water as control or placed on paper towels for mild drought treatment for 6 days and then soaked in water for 1 day for rehydration treatment. Plants were sampled at 1, 3, 6, and 7 days after treatment (dat). b Volumetric water content (VWC) at treatment initiation and sampling in pots (n = 4 independent replicates). Error bars denote SD. Relationships between the average of soil VWC and water potential were control treatment (74.0%, >−0.0031 MPa), mild drought 1-dat (55.7%, >−0.0031 MPa), mild drought 3-dat (35.4%, −0.0063 MPa), mild drought 6-dat (22.8%, −0.16 MPa), and mild drought 7-dat (20.0%, −0.24 MPa). c, d Pi concentrations of the seedlings in wild-type (c) and phr1 phl1 mutant (d) (n = 4 biologically independent pot replicates, three seedlings per pot). Error bars denote SD. ^*P < 0.05, ^**P < 0.01, and ^***P < 0.001, two-tailed Student’s t-test or one-way ANOVA with Tukey’s test (for 7-dat). C, D, and R denote control, mild drought, and rehydration treatment, respectively. e, f Total aboveground biomass (e) (fresh weight, FW) and maximum rosette radius (f); nine plants were grown per pot under control and mild drought conditions (n = 4 independent pot replicates). Error bars denote SD. Blue dots, pink dots, and purple dots indicate control, mild drought, and rehydration treatment, respectively. ^*P < 0.05, ^**P < 0.01, ^***P < 0.001, and ^****P < 0.0001, one-way ANOVA with Tukey’s test for each day versus 0 dat. g Photographs of Arabidopsis seedlings at 0 and 7 days after control or mild drought treatment. h Enlarged photographs of the central seedlings at 7 days after control or mild drought treatment. Bars, 1 cm (g, h).