LI-600 Porometer/ Fluorometer

Rapid insights into stomatal conductance and chlorophyll fluorescence

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The LI-600 is a compact porometer with an optional Pulse-Amplitude Modulation (PAM) fluorometer that measures stomatal conductance and chlorophyll a fluorescence over the same leaf area. The GPS receiver records location and altitude, and that, combined with measurements from the accelerometer/ magnetometer, provides data needed to calculate the angle of a leaf relative to the sun. Capable of completing these measurements in seconds, the LI-600 delivers the speed and precision required by researchers today.

Diagram showing the features of the LI-600 Porometer/Fluorometer.

Time-saving features for fast surveys

  • Automatic logging to complete a single measurement in seconds.
  • Simple, intuitive display shows the instrument status and most recent measurement.
  • Ergonomic, light weight design for easy handling.
  • GPS receiver for recording measurement location.
  • Barcode generator in the desktop software for creating custom barcode labels.
  • Barcode scanner to enter sample information and reduce manual data entry errors.
  • Built-in rechargeable battery for 8 hours or more of active use.

Measure anywhere at any angle

The LI-600 measures heading, pitch, and roll, and records latitude, longitude, and altitude. With these data, the LI-600 software calculates a leaf’s angle of incidence.

Leaf angle measurements

The angle of incidence of a leaf– its orientation to the sun at a given time and place–is a useful variable for understanding a plant’s architecture and its physiological responses to the environment. A leaf’s angle of incidence may change, for example, to maximize light intensity for photosynthesis, minimize light intensity to conserve water, or allow light through a canopy to lower leaves. Knowing the angle of incidence of a leaf can lead to insights into how light intensity drives photosynthesis, and into the differences in measurements taken on the same plant.

The LI-600 accelerometer/ magnetometer measures three variables–heading, pitch, and roll–and the GPS receiver records leaf location and solar position. The LI-600 software uses these data to calculate the angle of incidence for each leaf measurement, allowing researchers to evaluate a plant’s environmental status more thoroughly.

Diagram depicting the 'angle of incidence'.
Stomatal conductance (gsw) measured with a GPS-enabled LI-600. Georeferenced measurements from the LI-600 are easily viewed in mapping applications including Google Earth™ and Esri® ArcGIS®.


The LI-600 records your position using GPS data when a measurement is taken, giving you the ability to track locations and return to specific areas over time. The LI-600 records the date, time, latitude, longitude, and altitude of each measurement, and works with the accelerometer/ magnetometer to record the data needed to calculate a leaf’s angle of incidence.

How it works

The LI-600 brings together numerous innovative technologies to deliver fast, accurate, and dependable measurements in a compact, handheld device.

Stomatal conductance

The LI-600 uses an open flow-through differential measurement for quantifying transpiration (E) and stomatal conductance that enhances its measurement process. First, E is quantified by measuring the flow rate and water vapor mole fraction of air that enters and leaves the chamber. Meanwhile, total conductance to water vapor (gtw) is computed as a function of E and vapor pressures in the leaf and cuvette. Finally, stomatal conductance to water (gsw) is computed as a function of gtw and the boundary layer conductance to water vapor (gbw).

The advantages of the LI-600 measurement flow path include the following:

  • Flow rates that quickly flush through the small chamber volume and result in rapid stabilization for quick measurements
  • A differential measurement that is close to ambient conditions
  • Minimally disturbed light, CO2, and H2O during the measurement that eliminate the need for desiccant chambers or corrections for large diffusion gradients
  • Automatic matching that accounts for drift between the reference and sample sensors

Chlorophyll a fluorescence

Measurements of chlorophyll a fluorescence provide insights into photosynthesis, and, when combined with stomatal conductance, results in a more complete picture of the overall plant physiology and health. In addition to rectangular flashes, the LI-600 supports multiphase flashes (MPF), which can prevent underestimation of Fm (Loriaux et al., 2013) and thereby reduce bias in numerous fluorescence parameters.

Loriaux SD, et al. (2013). Closing in on maximum yield of chlorophyll fluorescence using a single multiphase flash of sub-saturating intensity. Plant Cell Environ 36:1755-1770.

Map with LI-600 GPS data points and text.

Light-adapted leaves

For light-adapted leaves, the LI-600 measures the quantum yield of fluorescence PSII), or the proportion of light absorbed by PSII used in biochemistry.

equation for light adapted leaves with the LI-600 Porometer Fluorometer

Fm is maximum fluorescence yield in a light-adapted leaf; Fs is steady-state fluorescence yield in a light-adapted leaf.

Dark-adapted leaves

For dark-adapted leaves, the LI-600 measures maximum quantum yield (Fv/Fm), or the maximum proportion of absorbed light that can be used to drive photochemistry.

equation for dark adapted leaves with the LI-600 Porometer Fluorometer

Fv is variable fluorescence yield in a dark-adapted leaf; Fm is maximum fluorescence yield in dark-adapted leaf; Fo is minimum fluorescence yield in a dark-adapted leaf.

Why measure stomatal conductance and chlorophyll a fluorescence?

Stomatal openings regulate the exchange of water vapor and CO2 between a leaf and the air. Stomatal conductance to water (gsw), which responds to light, CO2, temperature, and humidity, among others, is a measure of the degree of stomatal openness and the number of stomata. It is an indicator of a plant’s genetic makeup and physiological response to environmental conditions.

Measurements of chlorophyll a fluorescence can provide information about the leaf’s quantum efficiency, electron transport rate (ETR), non-photochemical quenching (NPQ), as well as an assortment of reactions that collectively protect a leaf when it absorbs excessive light energy.

diagram showing how conductance and fluoresence in a single leaf

Combined measurements of stomatal conductance and chlorophyll a fluorescence present a more complete picture of a plant’s physiological state than either technique alone.

Understanding these processes is important to many research applications, including genetic screening, agronomy, plant physiology, ecology, climate change research, and stress tolerance.

LI-600 Testimonial

See what Aaron Hogan learned while measuring 40 different tree species with the LI-600 Porometer/ Fluorometer!

Read About His Experience

How it is different

The LI-600 is designed to quickly survey plants under ambient conditions. You can configure the instrument to log a measurement automatically when parameters are stable, or you can log manually with the press of a button.

Reaches stability in seconds for speed and consistency

  • Reaches stability in seconds across a range of gsw rates.
  • Provides fast measurements on different species.
  • User-configurable stability criteria and automatic logging to record each measurement when it is stable.
LI-600 data set
Figure 1. Three time series of measurements taken at different times of day on three adjacent leaves of three plants. The series are overlaid to show that the instrument can complete measurements in 6 to 9 seconds at a range of gsw values. Data points when not clamped between leaves not shown for clarity. Measurements are one-side stomatal conductance (gsw) made on three adjacent leaves (orange is soy shortly after sunrise; gsw = 0.055, blue is soy near midday; gsw = 0.17, and green is tobacco at midday; gsw = 0.51). Data are the 2 Hz measurements from the LI-600.

Dependable data, day after day

  • Automatic, user-configurable matching of RH sensors ensures measurement of the true differential.
  • Pliable gasket material conforms to the leaf to minimize diffusion and bulk flow leaks.
  • Automatic leak detection to prevent measurement errors.
  • Infrared thermometer for fast, accurate leaf temperature measurements.
  • Built-in light sensor measures ambient photosynthetically active radiation (PAR) near the leaf.
  • Accelerometer/ magnetometer measures pitch, roll, and heading–leaf angle relative to the sun is calculated from those parameters and GPS information.
  • GPS receiver records date, time, latitude, longitude, and altitude of each measurement.

Fast-track your research

Watch the LI-600 complete six measurements in 60 seconds.

Extend your research to soil and the atmosphere

What drives one plant to thrive, and another to fail? How do you measure an entire field? Learn more by digging into soil flux measurements to study soil-plant dynamics. Automate and scale-up to the field with an eddy covariance system. Learn more about LI-COR ecosystem monitoring solutions.

Learn more

Software that simplifies your work

You can configure the LI-600 with ease – just set a few parameters in the computer software and you are ready to collect data. Each LI-600 can store up to four configurations, making it easy to switch from one protocol to another. You can save numerous configurations on your Mac or PC and share configuration files with colleagues. Configurations are easily loaded from the software onto the device through a USB connection.

Whether you are preparing for measurements, evaluating data files, or verifying the calibration, the computer software presents a simple, intuitive interface that lets you focus on the task at hand.

Keeps your focus on measurements

The instrument display presents you with the information that matters without distractions, so you can keep moving from sample to sample. You can view live data, the most recent measurement, and configuration settings, among others.

Complementary instruments for complete analysis

The LI-600 Porometer/ Fluorometer is ideal for high-speed stomatal conductance measurements on many plants in ambient conditions. In contrast, the LI-6800 Portable Photosynthesis System characterizes carbon assimilation and numerous other parameters under controlled chamber conditions.

When used together, the two instruments provide highly complementary data. For example, the LI-600 can be used to screen a large population and the LI-6800 can be used to measure selected individuals from that population in greater detail.

LI-600 LI-600 LI-6800 LI-6800
Rapidly screen up to 200 samples per hour to identify candidates for detailed measurements Measure detailed physiological and photosynthetic parameters, including light response curves and A/Ci curves
Measurements in ambient conditions Measurements in controlled conditions; capable of multiple independent controls, including light, CO2, H2O, and temperature
Easy to use, basic configuration options Sophisticated configuration options in an intuitive graphical interface
Chlorophyll a fluorescence in ambient light Chlorophyll a fluorescence with controlled light; capable of induction kinetics measurements
Icon for application note.

Read an application note with case studies describing how the LI-600 and LI-6800 work together.

Read the app note

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