Non-destructive measurement of water potential in plants is challenging with current methods. The Plant-Pressure-Ecotron (PPE) allows accurate measurement of water potential and transpiration rates of intact plants in the laboratory. Experimental plants can be exposed to different evapotranspiration requirements, e.g. by influencing light intensity or humidity and soil drying. By measuring the hydraulic conductivity of the soil-plant system and its components, the PPE is an optimal device for studying the tolerance of plants to drought. More information on plant water balance can be found here.

Structure and function

The PPE consists mainly of three parts; the pressure vessel, the transparent plant chamber (cuvette) in the atmosphere unit and the control unit.

The experimental plant is planted in the pressure vessel, which contains the substrate and plant roots. The transparent cuvette is fixed on the pressure vessel. It contains the above-ground part of the plant with stem and leaves. A leaf is cut and the pressure in the pressure vessel is increased until xylem sap emerges through the leaf cut. A sensor attached to this cut by means of a capillary registers the xylem sap leakage and transmits a signal to the control unit. The control unit regulates the vessel pressure until it reaches equilibrium pressure. The PPE measures the difference between atmospheric pressure before pressure buildup and equilibrium pressure after pressure buildup as plant water potential.

In addition, the PPE determines transpiration rates by the difference in humidity between the incoming and outgoing air in the cuvette, which is circulated by a fan. The strength of photosynthetically active radiation to illuminate the plant can be regulated and measured using a PAR sensor. In addition, the PPE allows automatic measurement of temperature differences and respiration rate.

Installation area (width x height x depth):

• ca. 1,200 mm x ca. 945 mm x ca. 500 mm

Other dimenions of the pressure chamber and the transparent hood on inquiry.

pressure chamber:

• pressure chamber (iØ 156 mm, height 328 mm) up to 20 bar, incl. certificate for pressure chamber
• temperature sensor  Pt 100 for measuring in pressure chamber headspace or soil cylinder
• oxygen sensor (automatic control oxygen in headspace)
• pressure sensor (automatic control of pressure)
• flange plate with opening (Ø6 mm) and holder for a plant seedling
• soil core cylinder made of PVC transparent (iØ 111 mm, height 270 mm)

transparent hood:

• acrylic cuvette (diameter: 200 mm, height: 505 mm)
• 4x LED boards (wave length maximum: red channel with 733, 677, 737 nm, white/blue channel with 448/580, 454/642 nm)
  • channels independently dimmable of each other in the range of 0 to 100%
  • light intensity of both channels up to 1,300 µmol/(s•m²)
• air humidity and temperature sensors in air in- and outtake
• fan to homogenize air
• PAR sensor
• adapter ring for pressure chamber with tube, capillary and wire connector
• meniscus sensor to automatically gain the actual meniscus level in dependence of the tensio of the plant seedling
• humidity unit to automatically control air humidity and the air change rate in the transparent hood
  • rel. air humidity ca. 40 % to ca. 90 %
  • air flow rate: 0 to 10 l/min
• water filled packed column with glass beads and recirculation pump

control unit:

• LAN socket
• voltage 110 or 230 V alternating current
• gas sockets for compressed air and nitrogen incl. stop, discharge and safety valves
• PLC, Siemens SPS 7
• 7'' colour display
• project generation, manual and automatic operating mode, graphical visualisation of actual data,
• status LEDs for overpressure notification

A gas supply of more than 20 bar is needed.