The Standard in

Plant Stress Measurement



Best in class - measures Y(II), ETR, Leaf temp, FV/FM, quenching, & has FM' correction option included.

This instrument provides many plant stress measuring protocols, at a low price. OS1p capability includes the fast measurements: Y(II) or ΔF/FM', ETR, leaf temperature, and FV/FM. It also provides the Hendrickson lake model quenching protocol to allow NPQ, Y(NPQ), and Y(NO) measurements. Rapid light curves are also included.


  • Stable Internal Actinic Light Source for reliable field and laboratory quenching tests
  • Loriaux (2013) FM' Correction Option or Square Topped Saturation Flash
  • Optional PAR clip - Measures PAR , leaf temperature and can be used for ETR measurements
  • Integrated GPS/GLONASS location receiver
  • 6 - 8 hour battery charge life
  • Automated modulated light set-up
  • Menu driven color graphic touch screen interface.
  • USB and removable SD memory card.
  • Data is stored in comma delimited files
  • Armored fiber optic light guide


Wide Range of Programmable Testing Protocols including:

  • Hendrickson lake model quenching- NPQ, Y(NPQ) & Y(NO)
  • Rapid light curves - includes: ETRMAX, α, Ik, & Im
  • Y(II) with PAR, ETR & leaf temp
  • FV/FM
  • The OS1p is designed to provide a cost effective, yet comprehensive plant stress measuring chlorophyll fluorometer. It is optimally designed to measure the light adapted protocol developed by Bernard Genty, ΔFM/FM' or Y(II), the Burke water stress assay, and the dark adapted protocols: FV/FM, Rapid Light Curves (for changing light conditions found under canopy and in aquatic measurements), and basic quenching measurement using the lake model Hendrickson protocol with NPQ, Y(NPQ) and Y(NO).

  • Parameters Measured and Protocols included:



    Quantum Photosynthetic Yield of PSII (or ΔF/FM' or Y(II)).


    Electron transport rate (w/optional clip).


    Photosynthetically Active Region value (with optional PAR clip).


    Leaf temperature (with optional PAR clip).


    Maximum Photochemical efficiency of PSII.


    A more sensitive detector of stress than FV/FM, but it does not measure plant efficiency.


    Minimum fluorescence.


    Maximal fluorescence.


    Variable fluorescence.

    FMS (or FM'):

    Maximal fluorescence with actinic illumination.

    FS (or F):

    Fluorescence under steady state conditions (prior to saturation pulse).

    Multi-Flash with FM' correction and ETR correction.


    RLC (Rapid light curves):



    A measure of a leaf's photosynthetic MAX capacity or maximum electron transport rate α is the initial slope of line at low PAR values created by relating ETR to PAR. It provides a measure of quantum efficiency.


    A measurement of the light intensity where light saturation dominates, or the minimum saturation level.


    PAR light intensity at ETRMAX.

    Quenching protocol:


    Hendrickson lake model quenching protocol:

    Y(NPQ), Y(NO), Y(II), NPQ, FV/FM.

    Kramer Quenching (standard):

    qL, Y(NPQ), Y(NO), Y(II), FV/FM.

    Puddle model parameters (standard):

    NPQ, qN, qP, Y(II), FV/FM.

    Quenching relaxation protocol (standard):

    qE, qM, qZ, qT, qI along with either puddle model, or Hendrickson parameters. Adjustable times for each.

    Optional PAR Clip

    Measures PAR and leaf temperature. It should be purchased for Y(II) and ETR measurements. The PAR Clip is also recommended for rapid light curves and quenching measurements because it allows the built-in actinic light source to remain at a stable light intensity during longer measurements.

    Light Sources:


    Saturation pulse:

    White LED with 690nm short pass filter. 15,000 μmols.

    Modulated light:

    660nm LED with 690nm short pass filter.

    Actinic light source:

    White LED to 3,000 μmols.

    Far red light:

    720nm LED with > 700nm long pass filter.

    Detection method:

    Pulse modulation method.

    Detector & Filters:

    A PIN photodiode with a 700nm ~ 750nm bandpass filter.

    Sampling Rate:

    Auto-switching from 10 to 10,000 points per second, depending on phase of test.

    Automated routine to optimally set the modulated light intensity.

    The modulated light may also be set manually.

    Multi-Flash FM' correction for all light adapted protocols.

    It may be turned on or off.



    Test Duration:

    Adjustable from 0.1 seconds to 12 hours.

    GPS location:

    Built in GPS / GLONASS 12 channel receiver with internal antenna.

    Storage Capacity:

    1 Gigabyte of non-volitile flash memory.

    Digital Output:

    USB removable storage device standard. Comma delimited files.

    SD/MMC data card.

    User Interface:

    640 x 480 graphic color touch screen.

    Menu driven software.

    Power Supply:

    Internal 12V, rechargeable nickel metal hydride battery.

    Battery Life:

    6 to 8 hours of continuous operation.


    7 in x 5.5 in x 3.25 in (17.8 cm, x 14 cm, 8.3 cm).


    3.6 lbs (1.62 kg).

    Specifications subject to change without notice.

  • FL-DC

    Dark adaptation clip


    Pouch of 50 clips


    Large universal tripod - extends from 1.4m to 3.2m.


    PAR clip


    Adjustable locking desktop arm


    70Ah Battey Belt

  • PDF document.

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Opti-Sciences, Inc.     8 Winn Avenue      Hudson NH 03051       USA      (603)883-4400

Opti-Sciences, Inc.

8 Winn Ave

Hudson, NH 03051, USA

Phone: (603) 883-4400

Fax: (603) 883-4410