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Looking deep inside of flowers may reveal their hidden secrets

Flowers are complex, three-dimensional structures that thrill us with their shapes and colors. Their diverse morphology and rich hues have evolved to attract pollinators and ensure successful reproduction in a 3D world, and yet we are often more familiar with them captured in 2D, in the form of photographs and artworks. 

A team of scientists from McGill University, Université de Montréal, and the Montreal Botanical Garden, have now developed a method of generating 3D images from photographs and other 2D sources. Photogrammetry is the technology used to obtain 3D information about physical objects and the environment through the process of recording, measuring and interpreting photographic images. This methodology has been extensively used in the field of geography, to reconstruct physical objects from aerial or satellite photographs. It has never before been used to understand the 3D structure of flowers.

The researchers developed a photogrammetry method to reconstruct 3D models of flowers based on numerous images taken from different angles using a digital, single-lens reflex camera, a turntable and a lightbox. They tested their method on 18 different species from the family Gesneriaceae, which includes primroses and African violets. Their results are published in the journal New Phytologist.

The researchers say that photogrammetry has the potential to boost research on flower evolution and ecology because it provides a simple way to access three-dimensional morphological data. Databases of flower structures – or even of the structures of complete plants – could give scientists and the public a way to finally see the unique features of plant species that usually remain hidden from view.

“The variety of shapes and colors seen in the plant world are difficult to capture with simple photography. That’s why I became interested in adapting technological tools to capture the form of flowers,” said Professor Daniel Schoen, who first had the idea of applying photogrammetry to flowers, while doing research at the Institut de Recherche en Biologie Végétale. “Understanding floral evolution is important because flowers are the principal drivers of plant diversification through speciation, a major determinant of plant biodiversity.”

“Together, the team developed something we think will help advance our understanding of how flowers diversify in response to their interaction with pollinators. Thanks to our 3D models, it’s possible to admire flowers from every angle.”

According to the researchers, the use of photogrammetry has real advantages compared to other existing methods, in particular X-ray microtomography, which is by far the most widely used method to build 3D flower models. 

“Photogrammetry is much more accessible, since it’s cheap, requires little specialized equipment and can even be used directly in nature,” said study lead author Marion Leménager. “In addition, photogrammetry has the advantage of reproducing the colors of flowers, which is not possible with methods using X-rays.”

The first results, although imperfect, were enough to convince Leménager to devote a chapter of her thesis to it. “The method is not perfected yet,” said Leménager. “Some parts of the flowers remain difficult to reconstruct in 3D, such as reflective, translucent or very hairy surfaces.”

The method is an important step towards understanding more about the development and evolution of flowers, and how they interact with their pollinators. At least 90 percent of flowering plants make use of pollinators to ensure their reproduction, and the 3D morphology of flowers is an important factor that attracts appropriate pollinators. In the past, the 3D structure of flowers was rarely studied, because it is difficult to quantify structures in 3D. 

“We have shown that photogrammetry works at least as well as more complicated and expensive X-ray methods for visible flower structures,” said study co-author Simon Joly. “Thanks to the living collections of the Montreal Botanical Garden, our study of plants from the Gesneriaceae family, like the African violet, demonstrates that 3D models produced using this technique allow us to explore a large number of questions about the evolution of flowers.”

By Alison Bosman, Staff Writer

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