Y(II) meter is designed as an affordable & reliable light adapted chlorophyll fluorescence system.

Y(II) or F/FM’ or (FM’ – FS) / FM’) is a time tested light adapted parameter that is more sensitive to more types of plant stress than FV/FM. A survey of existing research strongly supports this statement. While FV/FM is an excellent way to test for many kinds of plant stress and the health of Photosystem II, Quantum Yield of PSII or Y(II) is a test that allows the measurement of the efficiency of photosystem II under actual light adapted environmental and physiological conditions.

The new Y(II) meter includes:
1. Y(II) measurement & ETR measurement corrected for leaf absorptance.
2. Leaf absorptance  measurement including leaf transmittance using RGB sensors. (It may be used on larger Arabidopsis leaves.)
3. PAR measurement (photosynthetically active radiation near the leaf)
4. Leaf temperature measurement averaged over a large area.
5. FM’ correction at high actinic light levels, according to Loriaux 2013.
6. A long term automated “monitor fluorometer mode” that allows measurement day and night. Useful for laboratory work. There are holes in the base of the chamber to allow photosynthesis.
7. Humidity sensor

To make the light adapted test, Y(II), available to more people that need it, Opti-Sciences developed a system that does not require expensive fiber optics, but still follows the proven methods needed for reliable plant stress measurement. Y(II) is measured from the top of the leaf along with PAR or photosynthetically active radiation. Furthermore, leaf temperature is measured from the bottom over a large area, allowing a more reliable value.

Leaf absorptance is reliably measured using an integrating sphere; however, this new instrument provides a reliable measuring estimate of leaf absorbtance and absorptance change due to different field conditions.

The Opti-Science Y(II) meter - PAR Clip was created to improve upon previous industry designs and maintain an affordable price. By developing a bottom opening design, this new model prevents inappropriate opening when measuring leaves above the operators head, or when mounted on a tripod that occurs with some industry designs. As a result, the Opti-Science Y(II) meter allows one handed operation, and eliminates two handed operation.

This PAR light sensor is positioned to allow measurement of ambient PAR very close to the leaf and at the same angle as the leaf.

Cosine correction - When measuring PAR in ambient light or with internal illumination, one must not change the orientation of the leaf to make a measurement. Yield is a always measured at steady state photosynthesis so a change in orientation to a light source will cause an error. Cosign correction insures that leaves that are oriented at different angles to actinic light sources will be measured reliably.