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LI-600 and LI-600N Porometer/Fluorometers

The LI-600 and LI-600N are compact porometers with Pulse-Amplitude Modulation (PAM) fluorometers that simultaneously measure stomatal conductance and chlorophyll a fluorescence over the same leaf or needle area. A GPS receiver tracks location and an accelerometer/magnetometer records data needed to calculate a leaf's angle of incidence to the sun. Capable of completing these measurements in seconds, the LI-600 and the LI-600N deliver speed and precision.

  • SKU : E473-LI-600
  • Manufacturer: Li-Cor
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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 on one side of the leaf. 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 pressure 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 quickly flush through the small chamber volume and result in rapid stabilization for quick measurements
  • A differential measurement in close to ambient conditions
  • Minimally disturbed light, CO2and H2during the measurement eliminate the need for desiccant chambers or corrections for large diffusion gradients
  • Automatic matching accounts for drift between the reference and sample sensors
Map with LI-600 GPS data points and text.
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 gswvalues. 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.
Time-saving features for fast surveys
  • Simple, intuitive display shows instrument status and most recent measurement.
  • Ergonomic, lightweight design allows for easy single-handed operation.
  • GPS receiver records measurement location.
  • Barcode generator in the desktop software creates custom barcode labels.
  • Barcode scanner records sample information and reduces manual data entry errors.
  • Optional user-defined prompts in the measurement workflow help keep data organized.
  • Built-in rechargeable battery powers 8 hours or more of active use.


Stomatal Conductance

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.

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 and LI-600N support multiphase flashes (MPF), which can prevent underestimation of Fm‘ (Loriaux et al., 2013) and thereby reduce bias in numerous fluorescence parameters.


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 accelerometer/magnetometer measures three variables–heading, pitch, and roll–and the GPS receiver records leaf location and solar position. The LI-600/LI-600N 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'.