Chlorophyll Fluorescence Imager

Chlorophyll Fluorescence Imager

I. Product Overview

The Chlorophyll Fluorescence Imaging System is a professional instrument for plant photosynthesis research. Utilizing a high-sensitivity CMOS camera and LED light source control, it enables rapid, non-destructive detection and imaging analysis of chlorophyll fluorescence in plant leaves. The system integrates two core functions: OJIP rapid fluorescence kinetics measurement and PAM modulated fluorescence measurement, enabling comprehensive evaluation of plant photosynthetic system activity, light use efficiency, and responses to environmental stress.

Featuring a modular design with highly integrated hardware and software, the system offers a user-friendly graphical interface supporting bilingual Chinese-English switching. It is widely applicable for research and teaching in plant physiology, ecology, agricultural science, environmental science, and related fields.

II. Technical Specifications

Camera:

Resolution: 1608(H) × 1104(V)

Pixel Size: 9µm × 9µm

★Frame Rate: 100 fps

Pixel Depth: 12 bit

Interface Type: USB 3.0

Lens and Optical Parameters

★Focal Length: 12mm

★Maximum Aperture: F/2.8 (dynamically adjustable)

Horizontal Field of View (HFOV): Approx. 62.11°

Vertical Field of View (VFOV): Approx. 44.83°

Maximum Imaging Range: 50cm × 35cm at standard working distance

Light Source Parameters

Blue Light Wavelength: 450 nm excitation source for fluorescence excitation

Red Light Wavelength: 630 nm photochemical light for PAM measurement

Far-Infrared Light: 730 nm for specific measurement requirements

LED Brightness Range: 1% - 100%, peak intensity up to 1440 µmol/(m²·s)

Measurement Range

1. OJIP Measurement

Measurement Duration: 0.1 - 1.0 seconds, adjustable, recommended 1 second

LED Brightness: 1% - 100%, corresponding to 90-1440 µmol/(m²·s), 5% increments

2. PAM Measurement

Dark Adaptation Time: 0 - 3600 seconds, can be set to 0 to skip

Light Cycle Count: 1 - 100 cycles, number of cycles during light adaptation phase

Monitoring Duration: 10 - 120 seconds/cycle, monitoring time per cycle

Recovery Time: 60 - 600 seconds, dark recovery monitoring duration

Photochemical Light Intensity: 1000 - 30000, red light 630nm LED brightness value

Saturation pulse (Fm): 15%–100%, dark adaptation saturation pulse (450nm blue light)

Saturation pulse (Fm'): 15%–100%, light adaptation saturation pulse (450nm blue light)

Sampling Interval: 0.1 - 10.0 seconds, data acquisition interval

Measurement Accuracy

1. Fluorescence Intensity Measurement

Dynamic Range: 12-bit (0-4095)

Signal-to-Noise Ratio: >100:1

Repeatability: CV < 3%

Linearity: R² > 0.999

Sensitivity: Capable of detecting faint fluorescence signals

2. Parameter Calculation Accuracy

Fv/Fm: ±0.005

ΦPSII: ±0.01

qP/qN: ±0.02

NPQ: ±0.1

PIABS: ±0.05

3. Time Resolution

OJIP Mode: Minimum acquisition interval 10 ms

PAM Mode: Minimum sampling interval 100 ms

Exposure time: Adjustable from 100 ms to 1000 ms

Response time: <1 ms (LED light source)

4. Spatial Resolution

★ Imaging Resolution: 1608 × 1104 pixels

Pixel Size: 9µm × 9µm (sensor)

Actual Spatial Resolution: Approx. 0.3mm/pixel (at 50cm × 35cm field of view)

Field of View: Horizontal 62.11°, Vertical 44.83°

★ Imaging Area: Maximum 50cm × 35cm

III. Function Overview

1. OJIP Rapid Fluorescence Dynamics Analysis

The OJIP measurement mode enables rapid assessment of photosystem II (PSII) activity and light use efficiency in plants. By applying intense light excitation, it records the complete rise kinetics from initial fluorescence (Fo) to maximum fluorescence (Fm) within 1 second.

Measurement Principle:

Under dark-adapted conditions, intense light exposure causes gradual reduction of the PSII reaction center QA from its oxidized state, resulting in a rapid increase in fluorescence intensity. This process reflects the efficiency of the electron transport chain and the quantity/activity of PSII reaction centers.

Information Obtained:

O Point (Fo): Initial fluorescence when all PSII reaction centers are open

Point J: Approx. 2 ms, reflecting electron transfer from QA to QB (calculated)

Point I: Approx. 30 ms, reflecting the reduction state of the PQ pool

Point P (Fm): Maximum fluorescence when all reaction centers are closed

Key Calculated Parameters:

Fundamental Parameters: Fv = Fm - Fo, Fv/Fm (maximum photochemical efficiency)

Specific activity: Mo (initial slope), Area (QA reduction area)

Quantum yield: ΦPo (capture efficiency), ΦEo (electron transfer efficiency), ΦDo (thermal dissipation)

Energy flux: ABS/RC, TRo/RC, ETo/RC, DIo/RC

Performance index: PIABS (comprehensive performance index)

Application Scenarios:

Rapid screening of plant materials

Assessment of environmental stress levels

Monitoring changes in growth status

Comparing effects of different treatments

2. PAM Modulated Fluorescence Measurement

PAM measurement mode employs modulated fluorescence technology to monitor plant photosynthetic activity under varying light conditions. It distinguishes between photochemical and non-photochemical quenching, providing insights into plant photoprotection mechanisms.

Measurement Procedure:

Dark-adaptation phase: Plants fully relax in darkness, restoring all reaction centers to open states

Fo and Fm measurement: Apply measurement light and saturation pulses to determine dark-adapted fluorescence parameters

Light-adaptation phase: Apply photochemical light to simulate natural light conditions

Cyclic monitoring: Periodically apply saturation pulses to measure Fs and Fm'

Dark relaxation phase: Immediately apply far-red light after photochemical light shutdown to determine light-adapted minimum fluorescence (Fo')

Dark recovery detection: Shut down both photochemical and far-red light to monitor fluorescence recovery

Key parameters:

Fv/Fm: Maximum PSII photochemical efficiency (0.78–0.84 in healthy plants)

ΦPSII: Actual PSII photochemical efficiency (light energy utilization under illumination)

qP: Photochemical quenching coefficient (proportion of open reaction centers)

qN: Non-photochemical quenching coefficient (photoprotection capacity)

NPQ: Non-photochemical quenching (degree of heat dissipation)

ETR: Electron transport rate (indicator of photosynthetic rate)

Application Advantages:

Non-destructive measurement, repeatable monitoring

Distinguishes between photochemical and non-photochemical processes

Real-time monitoring of photosynthetic dynamics

Evaluates the efficiency of photoprotection mechanisms

★3. Data Analysis and Visualization

Fundamental fluorescence parameters (OJIP): F0, Fm, Fv, Fv/Fm

JIP-test Parameters: ΦPo, ΦDo, ΦEo, ψEo, δRo, ABS/RC, TRo/RC, ETo/RC, DIo/RC, REo/RC, PI_abs, M0, Vj, Vi, Area, Sm, N

Basic Fluorescence Parameters (PAM): F0, Fs, F0', Fv/Fm

PAM-derived parameters: ΦPSII, qP, qL, qN, NPQ, NPQ_SV, Rfd, Kf, Fs/Fm, Fs/Fm', PSII_closed, PSII_closed_Lake, actual_efficiency, excitation_pressure, Fm_decline_percent, efficiency_decline_percent, Vitality_Index, qP', qL_full, PSII_closed_Lake_full, ΦNPH, ΦNO, Y_NPH, Y_NO, Rfd'

Visualization

Fluorescence Images: Displays two-dimensional color fluorescence images for each parameter from basic fluorescence parameters (OJIP, PAM), JIP-test parameters, and PAM-derived parameters

Kinetic Curves: OJIP curve, relative variable fluorescence curve

Time Series Curves: PAM fluorescence intensity change curve

Parameter Tables: Clear display of parameter names, values, and units

4. Image Processing and Analysis

★ Automatic Region Segmentation: The system employs intelligent threshold segmentation algorithms to automatically identify plant leaf regions within images, excluding background and non-target interference. Users may enable or disable this feature as needed.

Manual Selection: For complex backgrounds or precise analysis of specific areas, users can directly select rectangular, circular, or irregular regions on Fm images, with real-time display of selection details.

★ Image Region Averages: Supports selecting points, rectangles, circles, or irregular regions on any image to view real-time regional averages.

Image Enhancement Processing:

Gaussian filtering for noise reduction

Adaptive contrast enhancement

Scientific color schemes (Jet Pseudocolor)

Color Bar Displaying Numerical Range

5. Data Management

★ Auto-Save Parameters: All measurement parameters (LED brightness, measurement time, cycle count, etc.) are automatically saved to the configuration file upon modification. They are automatically loaded upon next startup, eliminating the need for repeated setup.

Result Export Functionality:

Export Images: Export all analyzed images to PNG format while preserving original resolution

Parameter Export: Export parameter tables as CSV or Excel files for statistical analysis

Export All: One-click export of all images and parameter tables to a specified directory

File Naming Convention: Exported files automatically named in “Mode+Sequence+Image Name” format for clear content identification

6. System Settings

Language Switch: Click the language switch button in the top-right corner to instantly toggle between Chinese and English. Language settings are automatically saved and retained after restart.

Parameter Configuration: All measurement parameters support user-defined settings to accommodate different experimental requirements. The system provides parameter tooltips to help users understand the meaning and recommended range of each parameter.

Device Management: Automatically detects and connects cameras and LED controllers at startup. The status bar displays real-time device connectivity, facilitating prompt identification and resolution of hardware issues.

IV. Application Scope

1. Plant Physiology Research

- Photosynthesis mechanism studies

- Photosystem activity assessment

- Light use efficiency analysis

- Non-photochemical quenching research

- Electron transport chain functional evaluation

2. Environmental Stress Research

Drought stress response

Thermal stress effects

Photopressure adaptation

Heavy metal toxicity assessment

Early diagnosis of pests and diseases

3. Agricultural Applications

Crop variety screening

Cultivation condition optimization

Fertilizer effect evaluation

Pesticide damage detection

Growth status monitoring

4. Ecological Research

Plant photoadaptation studies

Community photosynthetic traits

Ecosystem function assessment

Climate change response

Biodiversity evaluation

Case Study

1: Assessing the Effects of Different Drought Severities on Plant Photosynthetic Performance

Method: Rapid measurement of Fv/Fm and PIABS using the OJIP method

Results: Mild drought caused a 5-10% decrease in Fv/Fm. As drought severity increased, the decrease exceeded 30%.

2: Screening Heat-Tolerant Crop Varieties

Method: Measuring ΦPSII and NPQ post-high-temperature treatment using PAM mode

Results: Heat-tolerant varieties maintained high ΦPSII (>0.5) and moderate NPQ (2–3) under high temperatures

3: Comparing Effects of Different Fertilization Schemes on Photosynthetic Efficiency

Method: Combined OJIP and PAM measurements for comprehensive photosynthetic performance assessment

Results: Optimal fertilization protocols enhance Fv/Fm and increase PIABS

4: Detect disease stress before symptom onset

Method: Continuous monitoring of Fv/Fm and OJIP curve dynamics

Results: Significant Fv/Fm decline detectable 1-2 days prior to symptom emergence