Environmental Control

The LI-6400XT's flow through design allows automatic, independent control of leaf chamber conditions including:

6400-40 fluorometer with light control Making light-controlled measurements with the LI‑6400XT and optional 6400‑40 Fluorometer

Learn more about how the LI‑6400XT measures photosynthetic responses to light, CO2, temperature, and humidity.



The integrated CO2 Injector System provides a constant CO2 input from 50 to 2000 µmol mol-1 (down to 0 µmol mol-1 with modification to the system) and can be controlled to within 1 µmol mol-1 of a target value at the leaf surface.

This system facilitates measurements at elevated CO2 concentrations and easily generates CO2 response curves. CO2 concentration can be set manually from the console or automatically with the use of Autoprograms to make measurements at a series of concentrations.

OPEN version 6.2 software now allows you to control internal CO2 (Ci), which can be important when creating response curves. Learn More


The Red/Blue LED Light Source, RGB (Red, Green, Blue) Light Source, and Leaf Chamber Fluorometer (all optional accessories) are integrated with the hardware and software of the LI‑6400XT System.

Light intensity is controlled over the entire range (0-2000 µmol m-2 s-1) through a feedback algorithm. Light curves can be generated automatically using Autoprograms and user-selectable light set points.


Leaf temperature is controlled by integrated Peltier coolers. Chamber temperature can be set to any value within ± 6 °C of ambient temperature. Temperature control is a standard feature of the LI‑6400XT; no external power supplies or accessories are required.

An optional Expanded Temperature Control Kit is available to increase the leaf chamber temperature range control.


The LI‑6400XT controls user-specified chamber humidity through the use of desiccant and by automatically varying the flow rate to null-balance. The input flow rate can also be held constant.

Inaccuracies and time delays due to water sorption on the air lines are eliminated by measuring the reference and sample water vapor concentrations in the sensor head.

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