Get rapid insights into stomatal conductance, chlorophyll fluorescence, and leaf angle for a variety of leaf sizes and morphologies, including many needles and narrow grasses.
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.
Combined measurements of stomatal conductance and chlorophyll a fluorescence present a more complete picture of a plant’s physiological state than either technique alone.
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.
Understanding these processes is important to many research applications, including genetic screening, agronomy, plant physiology, ecology, climate change research, and stress tolerance.
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.
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 and LI-600N measure 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.
The LI-600 and LI-600N measure heading, pitch, and roll, and record latitude, longitude, and altitude. With these data, the LI-600/LI-600N software calculates a leaf’s angle of incidence.
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.
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®.
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