The Standard in

Plant Stress Measurement



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

This instrument provided the most used plant stress measuring protocols, at a much lower 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
  • PAR clip optional - Measures PAR , leaf temperature and ETR
  • 8 hour battery charge life
  • Option for automated modulated light set-up
  • Designed to allow chloroplast migration (it does not measure qM)
  • Menu driven color graphic touch screen interface.
  • Data output by USB port and by removable SD memory card.
  • Measuring files and graph data open directly in Excel ®
  • 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.

    Ik =/α:

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


    PAR light intensity at ETRMAX.

    Hendrickson lake model quenching protocol:

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


    Optional PAR Clip

    Provides PAR and leaf temperature. It should be purchased for Y(II) and ETR measurements. The PAR Clip is also recommended for 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 690 nm short pass filter. 11,000 μmols.

    Modulated light:

    660 nm LED with 690 nm short pass filter.

    Actinic light source:

    White LED to 3000 μmols.

    Far red light:

    Above 740 nm.

    Detection method:

    Pulse modulation method.

    Detector & Filters:

    A PIN photodiode with a 700 ~ 750 nm 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.

    Storage Capacity:

    1 Gigabyte of non-volitile flash memory, supporting unlimited data sets and traces

    Digital Output:

    USB, SD/MMC 1 Gigabyte data cards.

    User Interface:

    Graphic color touch screen.

    Menu driven software.

    Power Supply:

    Internal 12V, rechargeable nickel metal hydride battery.

    Battery Life:

    8 to 12 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 kgs.

  • 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