Measuring Leaf Water Stress

Early detection of leaf water stress is critical for precision agriculture. Spectroscopy is well-suited for accurate measurement of water stress in plant leaves and provides an effective technique for nondestructive, rapid and accurate measurement. Water stress can signify overall plant physiological health and is important for agricultural assessment of nutritional health, diseases, crop quality and other critical factors. Knowledge of plant health and water stress can lead to precision irrigation strategies based on real data.

Water stress has an impact on a plant’s photosynthetic performance and the severity decides whether or not a plant can recover from damage inflicted with additional irrigation.

The RS-8800, NaturaSpec™, PSR+ and RS-3500 are high resolution/high sensitivity field spectroradiometers covering the full UV/VIS/NIR range from 350-2500nm. They are rugged, field portable instruments with all solid state photodiode arrays and no moving parts for reliable operation. They provide auto- shutter, auto-exposure and auto-dark correction for one-touch operation. They are available with a range of accessories including contact probe, Miniprobe, pistol grip, benchtop probe and leaf clip. For measuring leaf water stress the unique leaf clip is an invaluable resource. The leaf clip is designed for single-handed use in the field. It includes a built-in white reference and integrated light source that keeps heat away from your sample.

A researcher can use the leaf clip to measure leaf water stress in situ. The resulting spectra can show the primary water absorption feature wavelengths for analysis of water stress: 760,970,1200,1450 and 1950 nanometers. Changes in the red edge that indicate water stress (moving to shorter wavelengths) can also be noted as an indication of less chlorophyll production. All spectra are saved as ASCII files for use with third party software including ENVI, R2 and chemometrics software such as Camo Analytics Unscrambler. You can use the coefficients produced by your Unscrambler model to predict values in real time in DARWin LT Data Acquisition software running on a rugged tablet connected to a Spectral Evolution spectrometer or spectroradiometer. The optional tablet has a digital camera and GPS and tags photos, coordinates, voice notes and altimeter readings to your scans.

In addition, the DARWin SP Data Acquisition software which controls the instrument includes pull-down menus for 19 vegetation indices including WBI (Water Band Index) and NDWI (Normalized Difference Water Index).

A spectra taken with the leaf clip and PSR+ showing the water absorption bands and the red edge.

The NaturaSpec™, PSR+ and RS-3500 work with our unique leaf clip for detecting plant stress in the field.

The leaf clip includes a built-in white reference and is designed to keep the heat from the illumination away from your sample so that measurements can be accurate and non-destructive.