Evaluation of Plant Stress Monitoring Capabilities Using a Portable Spectrometer and Blue-Red Grow Light.

Area of Science:

• Plant physiology
• Remote sensing
• Spectroscopy

Background:

• Remote sensing provides non-destructive plant stress detection via chlorophyll fluorescence (CF).
• Traditional CF estimation methods often involve complex retrieval, spectral fitting, or modeling.
• Existing reflectance-based indices like NDVI and PRI have limitations in early stress detection.

Purpose of the Study:

• To evaluate a straightforward spectroradiometer and blue-red LED technique for measuring chlorophyll fluorescence (CF).
• To assess the capability of this CF technique in detecting plant stress compared to traditional methods.
• To determine the potential of CF monitoring for early stress indication in vegetation.

Main Methods:

• Measurements of chlorophyll fluorescence (CF) spectra from tomato plants treated with a photosystem inhibitor.
• Utilized a spectroradiometer with blue-red light emitting diodes (LEDs) for excitation and spectral capture (~650 to 850 nm).
• Compared CF-based metrics with traditional reflectance indices: Normalized Difference Vegetation Index (NDVI) and Photochemical Reflectance Index (PRI).

Main Results:

• The blue-red LEDs provided sufficient irradiance and spectral window to capture distinctive "two-peak" CF spectra.
• CF-based metrics detected vegetation stress earlier than NDVI and PRI, and visual inspection.
• The technique could distinguish plant health on a day-to-day basis, though within-day variations were noisy.

Conclusions:

• The developed CF monitoring technique is a flexible and scalable option for plant function data collection.
• This method effectively indicates early signs of vegetation stress.
• The technique is applicable from single plants to larger canopies, adaptable for various platforms (manned/unmanned vehicles).