Interrogation of local leaf hydraulics with AquaDust in maize. A) Schematic diagram and picture of a maize leaf with four different treatments to manipulate adaxial and abaxial transpirations $(Ead$ and $Eab)$⁠: suppressing transpiration $(E)$ by applying tape on both sides (BT), applying tape on AdT, applying tape on AbT, and a control region with NT (see Fig. 1D). Dashed lines labeled with a diagram of a razor blade show the section of the leaf tissue section that was cut and used to measure leaf water potential with a Scholander pressure chamber $(ψSPCleaf$⁠). Arrows indicate the approximate length of the section of leaf tissue used for leaf water potential measurement using Scholander pressure chamber $(ψSPCleaf)$⁠. B) Transpiration rate $(E,mmol/m2/s)$⁠, and assimilation rate $(A,μmol/m2/s)$ with four cases (BT, AdT, AbT, and NT) that correspond to the sites of measurements in A) (⁠$n=4$⁠, error bars represent the standard error). Two-tailed t-test confirms significant decline (P < 0.05) in E and A from the BT region compared to the AdT, AbT, and NT regions (*: P-value < 0.05, n.s.: not significant, see Supplementary Table S1 for quantitative values and analysis). See Materials and Methods (Eqs. 1 to 8) for the calculation of the various hydraulic conductances from these potentials. Conductances and architecture in each treatment area are as in Fig. 1A. C) to E) Measured values of whole-leaf potential (⁠$ψSPCleaf$—squares) and AQD potentials at adaxial $ψAQDad$—circles) and abaxial $ψAQDab$—diamonds) sides of the leaf (sample size: 14 plants, each point corresponds to one plant; error bars represent the standard error for 3 to 6 measurements collected per plant; see Materials and Methods and Supplementary Methods S3 for more details) as a function of xylem potential $(ψAQDxyl)$ for dark-adapted leaves with low transpiration rate (⁠$E<0.7mmol/m2/s$—C), for transpiring leaves $(Eab>0.7mmol/m2/s)$ with adaxial side taped (AdT—D), and for transpiring leaves $(Ead>0.7mmol/m2/s$⁠) with abaxial side taped (AbT—E). Red and dashed lines are one-to-one; black and dashed lines show uncertainty in the calibration of AquaDust (⁠$±0.15MPa$ (Jain et al. 2021)). F) Deviation $(Δψ)$ of $ψSPCleaf$ (squares), $ψAQDab$ (diamonds), and $ψAQDad$ (circles) from $ψAQDxyl$ as a function of F.I)$Eab$ for the case of AdT zone and F.II)$Ead$ for the case of AbT zone in well-watered maize $(ψAQDxyl=−0.5±0.25MPa)$ (sample size of 7 plants; each point corresponds to one plant; error bars represent standard error). Lines represent linear regression fit, and shaded zones represent $95%$ confidence intervals (see Supplementary Tables S2 and S3 for details). G) Variation of stomatal conductance (⁠$gs$—black stars), effective leaf conductance (⁠$KoxzSPC$ squares—Eq. 1), adaxial and abaxial outside xylem conductance (⁠$Koxzad$ and $Koxzab$—circles and diamonds—Eqs. 3 and 4) as a function of xylem potential based on AquaDust measurement in BT region $(ψAQDxyl)$⁠. H) and I) Variation of bundle-sheath conductance $Kbs$ (H) and of $Kmad$ and $Kmab$ (I), calculated for the AdT and AbT zones as a function of $ψAQDxyl$ (see Materials and Methods Eqs. 1 to 8, see Supplementary Table S4, S5, and S6 for definitions of effective conductances and fits (sigmoidal curves with shaded confidence intervals)).