Establishing vulnerability curves with the flow-through centrifuge method (cavitron)



Régis Burlett, José M. Torres-Ruiz, Melvin Tyree, Sylvain Delzon, Hervé Cochard1

Author Affiliations

1Université Clermont Auvergne, INRAE, PIAF, 63000 Clermont-Ferrand, France


This protocol describes the steps to establish a vulnerability curve to cavitation with the Cavitron: a flow-through technique that can be used on various sample types and size (depending on your setup), typically from 14 to 100 cm.

This protocol concerns cavitron set up for remote operation, based on image vision data acquisition.


The cavitron technique and some of its performances has been extensively described (Cochard 2002, 2005; Li, 2008; Cai 2010; Beikircher 2010; Wang T. 2014 and Burlett in prep). This technique is based on measurement of hydraulic conductance (k) of a xylem-bearing sample while the water column in the xylem is kept under tension by centrifugal force (P). The main advantage of the cavitron technique, is that it enables, at the same time, to (i) generate a controlled tension in the water column of the xylem (in the central part of the sample) due to centrifugal forces and (ii) to measure the hydraulic conductance which is defined as the amount of water flowing through a sample during a certain amount of time (water flow F) at a defined pressure gradient between the sample ends (∆P).

The pressure gradient is obtained by immerging the extremities of the sample in small water-filled reservoirs, fitted with holes  at different levels. Conductance measurement is done by monitoring, with a digital camera, the time taken by the air-water meniscus to cover a given distance.


Fig 1: General schematic of the cavitron system

(a) Camera; (b) light source (fiber optics or LED), (c) ultrapure water source, (d) solenoid valve, (e) Multifunction DAQ, (f) digital I/O board, (g) universal relay board, (h) KVM emitter, (i) KVM receiver




In early cavitron setup, the operator was required to work very close to the centrifuge in order to (i) read the meniscus position with a binocular, (ii) add water in the reservoir for the measurements and (iii) change the centrifuge speed. This implied to work in a dark and noisy environment, often in an uncomfortable position, and close to a potentially dangerous fast spinning rotor. These operating conditions do not comply with modern Health and Safety rules. We describe here the protocol of a new experimental setup (fig 1.) enabling completely remote operation of the cavitron, based on a software (Cavisoft, University of Bordeaux, France) which controls all the parameters required for conductance measurement, log data and computes variables of interest, in a user-friendly environment.

This technique can be used for branches, trunk baguettes, roots, long needles or floral stems. However, there is a general agreement that cavitron CAN NOT provide reliable vulnerability curve for samples having vessels longer than the rotor diameter (see Cochard et al. 2010; Choat et al. 2010; Torres-Ruiz et al. 2014, Martin-StPaul et al 2014 for further information) since it results in erroneous r-shaped curves.

So far, several rotors have been designed, allowing the measurement of different sample lengths. Typical sample lengths are 14cm; 27cm, 42cm and more recently 100cm.

NB: Please note that this protocol is meant as a user guide for the aforementioned setup, and not as guide to setup a cavitron. If you’re interested in building a cavitron, please contact the authors.


  •  High speed centrifuge (preferably temperature regulated eg. Sorvall RC5 …)
  • Custom rotor
  • Spectro meter cuvette
  • Water tank and tubing
  • Solenoid valve
  • Camera (eg. scout sca640-120gm, Basler, Germany)
  • Multifunction DAQ (eg. NI- USB 6008, National Instrument, USA)
  • Computer with a display resolution of 1920×1080.
  • Cavisoft software.
  • Shears
  • Razor blade
  • Calliper


a. Sample selection and preparation (in the field)

– Select a plant segment as straight as possible

– The diameter of the xylem (i.e excluding the bark) should not exceed 9.9 mm for standard cuvettes or 24.9 mm for centrifugation tube.

– Sample should be collected considerably longer than the rotor size.

* For conifer, at least 5 -10 cm at each extremities

* For angiosperms, see fig 2

Please refer to Wheeler et al. (2013) and Torres-Ruiz et al. (2015) for more details about angiosperms sampling issues


Fig 2: sampling protocol for angiosperm


-Collect sample when transpiration is low to minimize native embolism (early morning or low VPD conditions; not during hot and dry summers).

– Leaves (or needles) and side branches should be remove asap after collecting to avoid any transpiration and so cavitation.

-Label each sample and wrap the whole branch in wet papers (kim-wipes) Fig 3

-The samples should then be placed in a big sealed plastic bag and transported to the lab for storing.

(more details about the sampling procedure at


Figure 3: sample preparation






b. Cavitron preparation

– Turn on the computer, the centrifuge, the light source and the camera

– Set the temperature in the reservoir of the centrifuge to the desired value (typically 20°C)

– Open Cavisoft

– If the cavitron is equipped with automated speed control, connect the digital I/O board, and universal relay board.

– Check that the water tank is full of reasonably fresh, filtered (0.22 µm) measurement solution (10 mM KCl and 1 mM CaCl2). Change at least every week

– install the rotor with the 4 screws and washers provided, on the locations shown by the red dots on fig. 4. We recommend removing the rotor at least once a day to clean and dry both the tank of the centrifuge and the rotor

Figure 4 : rotor and sample installation







– Drill small holes (ca 1mm) in the reservoirs at 1.5 cm from the base for the upstream reservoir and at 1 cm from the base for the downstream reservoir.

c. Sample preparation (in the lab)

– It is possible to store the samples in the fridge (3 to 5°C , NOT in a freezer) for 10 -20+ days before measurement (depending on the species).

– Just before measurement, cut the samples at the desired length under water, remove the bark from both extremities and shave them with a sharp razor blade

NB: If your samples are curved, you might also consider to cut them a little shorter, as they tend to straightened as you spin faster, and can break the cuvette.

– For most conifer it is also recommended to remove bark entirely to avoid resin accumulation in the reservoirs (from centrifugation).

– Measure the diameter of the sample, below bark, at each extremities. Note the value in the software (PARAMETERS tab/branch diameter)

– Install the sample in the central part of the rotor (Fig 4) with both extremities enclosed in the reservoir (proximal part of the sample in the upstream reservoir / distal part of the sample in the downstream reservoir)

– Close the lid of the rotor with the 4 screws

– Close centrifuge lid. You are now ready to make your measurement…

d. measurement

All operations are now performed remotely from the software (see GUI in Fig 5).


Figure 5: screenshot of CaviSoft v5.0


  1. In the “PARAMETERS” tab (fig 6), enter the description of your sample, rotor identification number, name of operator, branch diameter and desired conductance unit.


Figure 6: Parameter tab


  1. Define the filename in which you want data to be stored (in menu: File/ “Save data As”)
  2. Connect the camera (click on the “camera connected” checkbox)
  3. Adjust light on the light source and camera exposure time to obtain sharp and bright meniscus (see Fig 7)



Figure 7: exemple of meniscus images and intensity profile


  1. Set the desired pressure (“Set cavitron pressure MPa” button)
  2. Start the centrifuge ( Press “START” button )
  3. Activate measurement mode (Press this icon    ) and focus on “measure mode” textbox
  4. Add water in the reservoirs (press keyboard down arrow)
  5. Select Region Of Interest (ROI) for automated meniscus determination (click “manually define downstream ROI” button, then double click on the downstream meniscus). If required adjust ROI positions parameters in the “Define region of interest” groupbox.
  6. Once the meniscus is located in the upstream ROI, press “Measure” button (or hit the space bar)

NB: The software now automatically monitor the meniscus distance, compute  the conductance in the desired SI unit (see Wang et al for details of computation) and save all parameter, raw data and variable of interest in the selected file.

Is short, computation is made by plotting meniscus- position-dependant function y (define in eq1) against time.

y = ln⁡〖x/x_o 〗+ ln (2R-x_o)/(2R-x)               [eq 1]

We can extract the conductance (K) from the slope (m) of this curve (fig8),

m =                       [eq 2]


x : position of the meniscus at time t (m)

x0:initial position of the meniscus (m)

2R: diameter of measured sample (m)

W : angular velocity (rad.s-1) 

Aw : Sample cross-section area (m²)


Figure 8: computation of eq 1 vs time








  1. Check that the measure is OK in the “AUTOMODE analysis” tab (Fig ). The bottom left graph should be a straight line, with minimum scatter. (see Wang et al for detail)
  2. Repeat at least 3 times for each pressure level.
  3. Change the pressure to the next step (“Set cavitron pressure MPa” button)
  4. Add water in the reservoirs (press keyboard down arrow)

REPEAT step 10 to 14 until the vulnerability curve is finished. (see an example of VC curve in Fig 9)


Figure 9: Vulnerability curve






Other resources

Before planning on doing a measurement with a cavitron, please read carefully the following articles:

Beikircher B, Ameglio T, Cochard H, Mayr S 2010. Limitation of the Cavitron technique by conifer pit aspiration. Journal of Experimental Botany 61: 3385-3393

Cochard H, Damour G, Bodet C, Tharwat I, Poirier M, Améglio T 2005. Evaluation of a new centrifuge technique for rapid generation of xylem vulnerability curves. Physiologia Plantarum 124: 410-418

Wang T, Burlett R, Feng F and Tyree MT. 2014. Improved precision of hydraulic conductance measurements using a Cochard rotor in two different centrifuges. Journal of Plant Hydraulics 1: e-0007

Notes and trouble shooting tips

Most of the cavitron rotors are designed to use commercially available reservoirs, either centrifugation tubes or spectroscopy cuvettes. While centrifugation tubes always state the maximum speed at which they can be spun, this information is not available for spectroscopy cuvette. Here is a rough estimate of the centrifugation capabilities of these cuvettes (observed on a 27cm rotor)

-Polystyrene reservoirs (PS) => up to 6000 to 7000 rp

-Polymethylmetacrylate reservoirs (PMMA ou plexiglas) => up to 8000 to 9000 rpm

-“UV”reservoirs (probably made in polycarbonate, though it’s never mentioned) =>  up to 12000 to 15500 rpm

To our knowledge, the most resistant cuvette is the following: UV cuvette macro, ref 759170, PlastiBrand, Germany.

Rotor imbalance

For fast rotation devices, it is very important that the rotor is well balanced in shape and weight. Extra care has been taken in the design of this honeycomb rotor, but perfect symmetry is not possible for cavitron application.

You might experience some imbalance problem, causing your centrifuge to enter a safe mode.

Please consult the user manual of your centrifuge for further information about error modes.

The imbalance problem typically appears toward a speed for which resonance occur (depending of the rotor design)

If necessary, you can use the 4 threaded holes (see red arrows, in fig 10) in the rotor in which you can screw one or two light-weight headless screws in order to maintain the balance of the rotor.

Figure 10: detail of reservoir holder + imbalance screws







Literature references

Beikircher B, Ameglio T, Cochard H, Mayr S (2010). Limitation of the Cavitron technique by conifer pit aspiration. Journal of Experimental Botany 61: 3385-3393

Burlett R, Inchauspé H, Torres-Ruiz JM, Souchal R, Cochard H, Delzon S .(2015) Guidelines for measurement of hydraulic conductance under tension with a cavitron. In prep

J Cai, U Hacke, S Zhang, MT Tyree (2010) What happens when stems are embolized in a centrifuge? Testing the cavitron theory  Physiologia plantarum 140 (4), 311-320

Choat B, Drayton WM, Brodersen C, Matthews MA, Shackel KA, Wada H, McElrone AJ, (2010) ‘Measurement of vulnerability to water-stress induced cavitation in grapevine: a comparison of four techniques applied to a long-vesseled species’, Plant Cell and Environment, 33, (9), 1502-1512

Cochard H (2002). A technique for measuring xylem hydraulic conductance under high negative pressures. Plant Cell and Environment 25: 815-819.

Cochard H, Damour G, Bodet C, Tharwat I, Poirier M, Améglio T. (2005). Evaluation of a new centrifuge technique for rapid generation of xylem vulnerability curves. Physiologia Plantarum 124: 410-418

Cochard H, Herbette S, Barigah T, Badel E, Ennajeh M, Vilagrosa A (2010). Does sample length influence the shape of xylem embolism vulnerability curves? A test with the Cavitron spinning technique. Plant Cell and Environment 33: 1543–1552.

Li YY, Sperry JS, Taneda H, Bush SE, Hacke UG. (2008) Evaluation of centrifugal methods for measuring xylem cavitation in conifers, diffuse- and ring-porous angiosperms. New Phytologist 177: 558-568.

Martin-StPaul N K., Longepierre D., Huc R., Delzon S., Burlett R., Joffre R., Rambal S. and H. Cochard (2014) How reliable are methods to assess xylem vulnerability to cavitation? The issue of ‘open vessel’ artifact in oaks. Tree Physiology 34: 894–905

Torres-Ruiz JM, Cochard H, Mayr S, Beikircher B, Diaz-Espejo A, Rodriguez- Dominguez CM, Badel E, Fernández JE (2014) Vulnerability to cavitation in Olea europaea current-year shoots: further evidence of an openvessel artifact associated with centrifuge and air-injection techniques. Physiol Plant 152: 465–474

Torres-Ruiz JM, Jansen S, Choat B, McElrone AJ, Cochard H, Brodribb TJ, Badel E, Burlett R, Bouche PS, Brodersen CR, Li S, Morris H, Delzon S. 2015. Direct X-Ray Microtomography Observation Confirms the Induction of Embolism upon Xylem Cutting under Tension. Plant Physiology 167: 40-43. doi: 10.1104/pp.114.249706.

Wang T, Burlett R, Feng F and Tyree MT. 2014. Improved precision of hydraulic conductance measurements using a Cochard rotor in two different centrifuges. Journal of Plant Hydraulics 1: e-0007

Wang, R., Zhang, L., Zhang, S., Cai, J. and Tyree, M. T. (2014), Water relations of Robinia pseudoacacia L.: do vessels cavitate and refill diurnally or are R-shaped curves invalid in Robinia?. Plant, Cell & Environment, 37: 2667–2678. doi: 10.1111/pce.12315

Wheeler JK, Huggett BA, Tofte AN, Rockwell FE, Holbrook NM (2013) Cutting xylem under tension or supersaturated with gas can generate PLC and the appearance of rapid recovery from embolism. Plant Cell Environ 36: 1938–1949

Health, safety & hazardous waste disposal considerations

This technique is based on potentially very dangerous centrifugal forces. Great care must be taken in the rotor design to prevent any mechanical breakage of the rotor and to ensure good balance of mass.