Leaf water potential measurements using the pressure chamber: Synthetic testing of assumptions towards best practices for precision and accuracy
2022
Rodriguez‐Dominguez, Celia M. | Forner, Alicia | Martorell, Sebastia | Choat, Brendan | Lopez, Rosana | Peters, Jennifer M. R. | Pfautsch, Sebastian | Mayr, Stefan | Carins‐Murphy, Madeline R. | McAdam, Scott A. M. | Richardson, Freya | Diaz‐Espejo, Antonio | Hernandez‐Santana, Virginia | Menezes‐Silva, Paulo E. | Torres‐Ruiz, Jose M. | Batz, Timothy A. | Sack, Lawren
Leaf water potential (ψₗₑₐf), typically measured using the pressure chamber, is the most important metric of plant water status, providing high theoretical value and information content for multiple applications in quantifying critical physiological processes including drought responses. Pressure chamber measurements of ψₗₑₐf (ψₗₑₐfPC) are most typical, yet, the practical complexity of the technique and of the underlying theory has led to ambiguous understanding of the conditions to optimize measurements. Consequently, specific techniques and precautions diversified across the global research community, raising questions of reliability and repeatability. Here, we surveyed specific methods of ψₗₑₐfPC from multiple laboratories, and synthesized experiments testing common assumptions and practices in ψₗₑₐfPC for diverse species: (i) the need for equilibration of previously transpiring leaves; (ii) leaf storage before measurement; (iii) the equilibration of ψₗₑₐf for leaves on bagged branches of a range of dehydration; (iv) the equilibration of ψₗₑₐf across the lamina for bagged leaves, and the accuracy of measuring leaves with artificially ‘elongated petioles’; (v) the need in ψₗₑₐf measurements for bagging leaves and high humidity within the chamber; (vi) the need to avoid liquid water on leaf surfaces; (vii) the use of ‘pulse’ pressurization versus gradual pressurization; and (viii) variation among experimenters in ψₗₑₐfPC determination. Based on our findings we provide a best practice protocol to maximise accuracy, and provide recommendations for ongoing species‐specific tests of important assumptions in future studies.
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