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  • Hyperspectral Imaging Leads to New Art Form, Greener Lawns

Photonics Spectra
Jun 2000
Dan Drollette

England's fields may soon stay green even when the grass is dead, thanks to hyperspectral imaging genetics -- and avant-garde art.

For a decade, British artists Heather Ackroyd and Dan Harvey have incorporated grass in their work. ("You might say it was grass that brought us together," said Harvey.) After observing the pale outline created by a ladder left on a lawn for a few days, the duo decided to make sod into a photographic medium.

But the award-winning pair faced two hitches familiar to photography's first practitioners: how to get more than a bare silhouette from their materials, and then make the image permanent.

The artists answered the first question by approximating conventional photography. They placed their photosensitive surface -- a living mini-lawn -- in a giant darkroom. There, they exposed it to the light of a 400-W projector bulb passing through a negative for prolonged periods. The varying densities of the negative's lighter and darker areas produced a full range of midtones by controlling the light levels in each area. "Wherever the light falls, you get chlorophyll, or green," said Harvey. "The more light, the darker that part of the picture."

The original 4 x 6-ft photograph of Mother and Child consists of neither computer pixels nor grains of silver halide, but blades of a new grass variety created with the help of hyperspectral imaging. © Heather Ackroyd and Dan Harvey/Santa Barbara Museum of Art, 1998.

But the picture disappeared after they removed it from the darkroom. When the lawn was kept alive, every blade turned green after a few days of sunlight. When it was killed, the chlorophyll molecules broke down in a biochemical process called senescence, turning everything into a yellow-brown smudge.

To solve this problem, the artists collaborated with biochemists from the Institute of Grassland and Environmental Research under a Sci-Art grant from the Wellcome Centre for Medical Science. "Working with the artists made us scientists think about hyperspectral imaging for studying grass," said Howard Thomas, head of the cell biology department.

Institute scientists knew that a natural variation of meadow fescue stayed green despite heat, frost and drought. To track the responsible biochemical pathways in a nondestructive manner, they fitted a liquid crystal tunable filter made by Boston-based Cambridge Research & Instrumentation Inc. to a hyperspectral, cooled, SenSys CCD camera from Roper Scientific Inc. of Tucson, Ariz.

The system's 400- to 720-nm range tracks the interplay among the dozens of pigments in living grass, including carotenoids (responsible for yellows, oranges and some reds) and anthocyanins (reds and purples). Usually, the chlorophyll's green overwhelms all other pigments, but when chlorophyll senesces, the other colors appear.

By studying these processes, the scientists could manipulate the gene that enables chlorophyll to resist senescence and stay green for months longer. Helen Ougham, a principal research scientist at the institute, pointed out that prolonged exposure to sunlight will eventually bleach the grass, but until then "[it's] still green, like the dried plants in a herbarium."

The institute plans to market its new grass for use on the nation's parks, lawns and golf courses within two years. The artists' and scientists' work will continue with the aid of a government grant. Their multidisciplinary collaboration resulted in a 30,000 euros L'Oreal Art & Science of Color Prize earlier this year.

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