DOES POTASSIUM IMPROVE PLANTS RESPONSE TO WATER DEFICIT?

Figure 1: Stomatal conductance (gs; A) and midday stem water potential (SWP; B) of fully irrigated vines (full; blue symbols) and vines experiencing repeated droughts (red) while receiving 5 (circles) or 60 (triangles) mg K in irrigation.

Figure 2: Evapotranspiration (A; ET) and biomass from cuttings (B) of fully irrigated (blue boxes) and repeatedly droughted vines at 5 and 60 mg K L-1 fertigations. Add second y axis about deltas for 5 and 60 ppm.

Figure 3: Stem water potential (SWP) versus stomatal conductance (gs) in fully irrigated and drought vines in 2020, 2021, and 2023. B) Soil available water versus relative evapotranspiration (ET divided by ET before the drought event).

Figure 4: Recovery speed from drought as a function of VPD. A) Recovery of the 5 and 58 treatment in the week after rehydration. For panel A use only data from 2023 (only in 2023 Emilio measured the recovery of gs almost every day. Panel B- the same as panel A, but for K. Panel C- bar graph comparing the number of days it took K to reach 80% of the max for each treatment.

Figure 5: Potassium’s contribution to air vapor deficits. A) Stomatal conductance (gs) relations to VPD in 5 and 58 mg K L-1 fertilized vines in 2021-2023. B)

Figure 6: Vines’ leaf area (LA) in full irrigation or terminal drought under 5 (orange line) or 58 (green) mg K L-1 fertilization. Lines denote daily means and ribbons enclose the standard deviation.

Figure 7: Leaf mineral substitutes. Leaf K and Mg concentrations for vines in 5 or 58 mg K L-1 fertilization in July 2020, 2021, and 2023. Vines were fully irrigated (blue boxes) throughout the season or experienced periodic droughts (red). Horizontal lines mark medians, boxes enclose the 0.25 to 0.75 interquartile, whiskers extend to the min and max values, and points mark outliers.

SI1: Drought effect on water use. Crop coefficients (KC) during 2020-2021 droughts (circles) and recovery (triangles) stages for vines in 5 or 58 mg K L-1 fertilization.