Viewing Data in the Field
OPEN uses the console's backlit 8 x 40 character graphical
display to show any 12 experimental variables at once,
on three user-defined lines. The display is quickly changed
by moving a cursor to the line you wish to change and pressing
a letter key corresponding to a display set or using the
left and right arrows to scroll through all of the variables.
Real-time graphics allow you to carefully examine the
approach to steady state for up to 24 variables with 3
plots per graph set. This avoids the difficulty in determining
whether steady state has been achieved when viewing in
text mode. Measured or computed variables can be used in
plots or strip charts. Up to 8 sets of plots can be defined
and stored.
Data Logging
Any or all of the default 13 computed and 55 measured
variables may be logged manually by pressing a button on
the sensor head or keypad. Data can be logged to non-volatile
flash memory, removable compact flash cards, or output
to the RS-232 port. Data can be logged manually or automatically
using an AutoProgram.
For example, if you wanted to automatically collect A-Ci
data, you would first set the desired chamber environmental
conditions for temperature, humidity, light (if using the
6400-02B or 6400-40) and starting CO2. Once
the leaf is acclimated to these conditions, start the A-Ci
Curve AutoProgram. This Auto-Program prompts for the CO2 concentrations
at which measurements will be logged, the minimum and maximum
time between measurements, and the stability parameter(s)
that must be achieved before each measurement is auto-matically
logged. These parameters can be standard deviation, coefficient
of variation, and/or slope of any set of variables. From
then on, it's all automatic: for each of the specified
set points, the leaf chamber is brought to that concentration.
After the minimum wait time has elapsed, the system starts
checking for stability. Once that occurs (or the maximum
time elapses), the data are logged, and the cycle repeats
for the next set point. All the while, the other environmental
controls are maintaining their set points, providing stable
conditions for your experiment.
Flexible Software
Virtually any type of calculation may be done with each
measurement. In addition to standard gas exchange parameters,
equations are included for computing leaf surface humidity,
leaf surface CO2 mole fraction, Ball-Berry Index and others.
Programs and data are stored in readable ASCII format.
Using the on-board editor, you can open an existing list
of computations, for example, modify it to suit your needs,
and then save it under a new name.
Software updates are always free and can be downloaded
to your LI-6400XT. This makes the continued software development
straightforward and guarantees that your LI-6400XT will
stay current.
Multi-Phase Flash Option for the 6400-40 Leaf Chamber Fluorometer
For users of the 6400-40
Leaf Chamber Fluorometer, OPEN 6.0 and above enables a multiphase flash option for the saturating pulse.
Assessing Fv in either light- or dark-adapted measurements requires application of a saturating flash of light to fully reduce QA, the primary acceptor of PSII. In many conditions, especially high-light adapted field plants, it is difficult to achieve full reduction of the QA-PQ pool with the usual rectangular flash (RF, Figure 1) method, which results in an underestimation of Fm', ?PSII, and ETR (Earl and Ennahli, 2004; Markgraf and Berry, 1990). The multiphase flash protocol (MPF, Figure 1) can be used under conditions when it is difficult to fully-saturate the plant material with a normal, rectangular flash (RF) in order to derive true estimates of Fm', ?PSII , and ETR within approximately one second (Loriaux et al., 2006).
With Version 6.0 OPEN software and above, the LI-6400/6400-40 System supports both the rectangular and multiphase types of saturating flashes. The RF type provides a single, saturating pulse of light for a short duration and Fm’ is determined from the maximum value of fluorescence during that pulse. The MPF type uses three phases, including a ramp of intensities, within a single flash of 1.5 to 2 s in length (Figure 1). Flash intensities and length are user-defined. After the multiphase flash is applied, Fm’ is determined from the y-intercept of a plot of fluorescence vs. 1/ intensity (Figure 2).
Figure 1. Rectangular flash (RF) method: a saturating multiturnover flash (Q) of 400 to 1200 ms duration. Multiphase flash (MPF) method: (1) high, nearly saturating Q for approximately 250 ms to reduce QA-PQ pool; (2) ramp of declining Q for about 500 ms; (3) return to the initial high Q for approximately 250 ms to check for flash-induced non-photochemical quenching (qN).
Figure 2. Fm' values from phase 2 of the MPF method are regressed against 1E4/Q and extrapolated to estimate the maximal fluorescence at infinite flash intensity.
References
Markgraf, T. and J. Berry. 1990. Measurement of photochemical and non-photochemical quenching: correction for turnover of PS2 during steady-state photosynthesis. Curr. Res. Photosynth. 4:279-282.
Earl, H.J. and S. Ennahli. 2004. Estimating photosynthesis electron transport via chlorophyll fluorometry without photosystem II light saturation. Photosynth. Res. 82:177-186.
Loriaux, S. D., R. A. Burns, J. M. Welles, D. K. McDermitt, and B. Genty. 2006. Determination of maximal chlorophyll fluorescence using a multiphase single flash of sub-saturating intensity. Poster Presentation. August, 2006. American Society of Plant Biologists Annual Meetings, Boston, MA.
New! Open 6.1 Software
LI-COR continues to innovate on the OPEN software platform for the LI-6400/LI-6400XT. OPEN 6.1 is the latest available version of the software. OPEN 6.1 features and benefits include:
• New and improved software tree structures. This new menu structure simplifies instrument calibration and configuration routines, improving the user’s experience with the instrument. The example below illustrates the installation of a new light source.
The tree structure makes all calibration or configuration options available from one screen. Users can easily view and navigate a single “tree” of options, eliminating the need to go multiple places to select calibration and configuration options.
• Stored histories of calibration and matching. OPEN 6.1 makes it easy to revert to previous user calibration settings, or factory settings.• XML information included in data files. Extra information about configuration and environmental control settings is provided in the instrument’s data files. This enables quick and easy troubleshooting of an experiment, long after the data has been collected.
• Improved Multiphase Flash (MPF) Protocol. MPF, also available in OPEN 6.0, provides a method to quench hard-to-saturate leaves when doing chlorophyll fluorescence measurements. OPEN 6.1 improves the MPF method by adding vertical, horizontal, and combined graph bars to ease determination of the appropriate phase timing.
• Option to create Excel data files on console. (Also available with OPEN 6.0) Excel files created on the console can be directly imported into Microsoft Excel. These files already have Excel formulas embedded, allowing for easy post-processing of data. Users can change a single variable such as leaf area and monitor the changes in conductance, assimilation, etc.
• Support for the new 6400-17 Whole Plant Arabidopsis Chamber and 6400-18 RGB Light Source. OPEN version 6.1 is required to use these new accessories.
OPEN 6.1 software is available for instruments with either the 200 MHz or 400 MHz boards, and can be downloaded here. Older instruments can be upgraded to a 400 MHz board, LI-6400XT features, and OPEN 6.1 software with the 6400-926 XT Upgrade Kit. Contact LI-COR or your LI-COR distributor for details.
