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.
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.
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.
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:
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.
For light-adapted leaves, the LI-600 measures the quantum yield of fluorescence (ΦPSII), or the proportion of light absorbed by PSII used in biochemistry.
Fm’ is maximum fluorescence yield in a light-adapted leaf; Fs is steady-state fluorescence yield in a light-adapted leaf.
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.
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.
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.
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.
Watch the LI-600 complete six measurements in 60 seconds.
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.
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.
"The LI-600 provides us snapshots of stress via chlorophyll fluorescence and was a breeze to use. We conducted all measurements (60 plants) in less than an hour. We could use the LI-600 to then ask really high-resolution questions about temporal variability in stress: instantaneous, days, or weeks, kinds of questions that are difficult with an 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|
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