Plant Stress detection glasses

The plant stress detection glasses work by absorbing green light (chlorophyll reflection band) and transmitting in the red and blue spectral regions (the chlorophyll a and b absorption bands) (see graph below). Because green light is absorbed, healthy plants appear black. Plants which are under stress have altered chlorophyll absorption, which is seen on spectral reflectance curves as increases in reflection. Thus when wearing the glasses, stressed plants appear brighter.

Plant stress detection glasses Light transmission

Graph showing the regions of the wavelength that are observed by the viewer after the glasses filter out the green light. Transmission of the blue and red light gives their special plant stress detection capability. Graph by R. Brock

I have used the glasses for evaluating forest damage. Trees with dead red-brown foliage glow like a “roman candle”. In late June, 2001, I was in a helicopter field-checking a predictive forest damage map. We were spotting damage (stress) that was not seen on the ground. The figure below shows a normal colour photograph of mountain pine beetle-killed pine. There are several stages of foliage discolouration.

Picture 1: Colour photograph of mountain pine beetle-killed lodgepole pine.

The plant stress detection glasses emphasize the red and yellows and make green trees below. I have modified the above photograph to give a realistic rendition of what the scene would look like to the wearer of the glasses

Picture 2: Simulated view of stressed pine when wearing glasses.

In one particular case, I spotted the tell-tale signal of a stressed tree. We circled in the helicopter. It was obvious to those wearing the glasses. I took off my glasses to photograph the tree. I could not see the tree without the glasses, Picture 3 below.

Picture 3: Stressed lodgepole pine seen from the helicopter.

The photograph (Picture 3 above)I took from the helicopter with normal colour film showed a very slightly discolored crown, which in the photo, if I hadn’t known which tree to look for, I would have missed it completely. We felt that the stressed tree was affected by a needle cast disease.

Picture 4: Simulated view of the stressed pine when wearing the glasses. The bright yellow spots throughout the canopy are stressed crown.

Later, we visited the site on the ground, and again we could not find the exact tree, since we could not see the damage in the crown. Examine the photos carefully. You will see that the yellow spots in the canopy can be matched with slight discolouration of some tree crowns.

The glasses make healthy plants look black.

Stressed plants “glow”

The greater the amount of dead, dry, red-brown foliage, the brighter is the glow.

They work best for aerial observations, but they can also be used on the ground.

They work best under sunny conditions, but can also be used under cloudy conditions.

Do not wear while driving a vehicle since you cannot see green light.

For information for ordering the plant stress detection glasses, click here.