Measurement of leaf xylem water potential and transpiration during soil drying using a root pressure chamber system
Simultaneous measurements of leaf water potential (ψleaf) and transpiration rate (E) for varying soil moistures (θ) is necessary to identify the hydraulic constrains on transpiration as the soil dries. However, continuous and accurate measurements of ψleaf in intact plants remain challenging. This work aims at describing a root pressure chamber system which allows high resolution measurements of the relationship between ψleaf and E during soil drying. The root pressure chamber is equipped with a cuvette where E is changed by altering the light intensity and air humidity. The belowground part of a plant, typically grown in soil-filled columns, is enclosed in a pressure chamber and the shoots in the cuvette. The chamber and the cuvette are connected to a main controller where different parameters are regulated and monitored. ψleaf is determined by applying the pneumatic pressure necessary to bring the xylem sap to the cut of a leaf. Sensitivity of different parameters was conducted with a series of E and θ using pearl millet as a model plant. ψleaf was measured at increasing and decreasing E for different θ. The results show that the method was sensitive to 0.1 bar (10 kPa) and the measurements of ψleaf were accurate in this range. The temporal resolution of the measurements of ψleaf was in the order of 5-10 min. E measured by the root pressure chamber system and by the balance matched well. In summary, the method allows accurate measurements of the ψleaf (E) relation in intact plants.
Cai, G., Ahmed, M.A., Reth, S., Reiche, M., Kolb, A. and Carminati, A. (2020). Measurement of leaf xylem water potential and transpiration during soil drying using a root pressure chamber system. Acta Hortic. 1300, 131-138
meniscus, pearl millet, plant hydraulic conductance, root pressure chamber, transpiration rate