With Flying Colours

Laura Junker and Ingo Ensminger
Wednesday, October 26, 2016 - 12:57pm
Carla DeMarco
A study out of U of T Mississauga looks at changing colour of autumn’s leaves

The colourful spectacle at this time of year when leaves turn from greens into beautiful yellows, oranges and reds in the fall is a sight to behold, but it takes on a whole new level of intrigue for PhD student Laura Junker from the Department of Biology and her supervisor Professor Ingo Ensminger, who are studying the correlation of colour changes and the photosynthesis process in sugar maple leaves.

“Although it is well known that leaves change colours in the fall, we have assessed how these changes are caused by variations in photosynthetic pigments,” says Junker.

Autumn leaves“When the green pigments disappear, and yellows and oranges dominate, we know that photosynthesis decreases and so leaves will no longer take up CO2 from the atmosphere. Pigment changes therefore indicate how much CO2 can be taken up by a tree, and because the pigment changes also affect the optical properties of the leaves, we can use equipment, be it hyperspectral sensors or even digital cameras, for the remote detection of pigment changes to predict photosynthetic CO2 uptake from the atmosphere.”

In their study, “Relationship between leaf optical properties, chlorophyll fluorescence and pigment changes in senescing Acer Saccharum leaves,” published in the journal Tree Physiology, Junker and Ensminger also compared the versatility of hyperspectral and digital image data for tracking the decline in photosynthesis in sugar maple during the fall.

“Our goal was to determine the optical fingerprint of the transition from summer to fall and eventually the programmed deterioration of the leaves,” says Junker.

“With our measurements of leaf optical properties we can now monitor health and productivity of a leaf without touching it, and precisely determine the end of the growing season. In addition, we did also show that cheap digital imaging technology could provide almost identical detail as what we obtained from the expensive hyperspectral sensor.”

Based on these results Ensminger’s lab will now scale up this approach. Using optical sensors mounted on small, unmanned aircrafts or drones, his lab will determine plant performance over larger areas of vegetation.

“We will test this technology to assist in large-scale tree breeding programs, and we will aim to monitor the health and performance in breeding populations of the Canadian Forest Service that are several hectares in size,” says Ensminger.

“Beyond breeding, our goal is also to use this powerful technology to better assess seasonal variation in photosynthesis and how warming climate affects plant productivity.”