LI-COR LI-600, Instruction Manual

Page: 88 / 131

9-1
Section 9.
Theory of operation
The LI-600 is equipped to measure two different aspects of
leaf photosynthesis. The porometer uses a mass balance for
water vapor flux from the leaf to compute stomatal con-
ductance. The fluorometer uses optical techniques to
probe the quantum yield of photosystem II.
The LI-600 also has a GPS receiver and an accel-
erometer/magnetometer that measures the pitch, roll, and
heading of a leaf. Those measurements, along with
GPS information, are used by the LI-600 software to cal-
culate a leaf's angle of incidence.
This section describes the theory and equations behind
these measurements and provides an overview of other
sensors in the LI-600.
Leaf porometer
The LI-600 porometer is an open system. Stomatal con-
ductance (
g
sw
) is computed from transpiration ( E ) in a leaf
cuvette and leaf temperature ( T
leaf
) is measured by a non-
contact infrared thermometer. Transpiration is computed
from the difference in H
2
O in an air-stream flowing
through a leaf cuvette ( Figure 9-1 on the next page).