The hidden secrets of flowers

To better understand the evolution of flowers, researchers from Montreal are harnessing photogrammetry - a technique commonly used by geographers to reconstruct landscape topography. This is the first time scientists have used the technique to study flowers.

The team, including researchers from McGill University, Université de Montréal, and the Montreal Botanical Garden, published the results of their work in the journal New Phytologist .

Photogrammetry uses information gathered from photos taken from different angles. Thanks to the triangulation of common points present on the photos, it’s possible to reconstruct a 3D model of a flower. Colours are then applied to the 3D flower using information from the photos.

Flower of Schlumbergera sp. Specimen from the collection of the Montreal Botanical Garden.

According to the researchers, photogrammetry has the potential to boost research on flower evolution and ecology by providing a simple way to access three-dimensional morphological data. Databases of flowers - or even of complete plants - could give scientists and the public a way to finally see the unique features of plant species that remained hidden from view.

-The variety of shapes and colours 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,- says McGill University 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,- says Professor Schoen.

Flower of Aeschynanthus splendidus. Specimen from the collection of the Montreal Botanical Garden.

-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,- he says.

Attracting pollinators by shape and colour

Flowers are complex and extremely varied three-dimensional structures. Capturing their forms is important to understanding their development and evolution. 91 per cent of flowering plants interact with pollinators to ensure their reproduction in a 3D environment. The morphology and colours of the flowers act like magnets on pollinators to attract them. Yet the 3D structure of flowers is rarely studied, the researchers explain.

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, say the researchers.

Flower of Phalaenopsis sp. Specimen from the collection of the Montreal Botanical Garden.

"Photogrammetry is much more accessible, since it’s cheap, requires little specialized equipment and can even be used directly in nature,- says Marion Leménager, a doctoral candidate in biological sciences at Université de Montréal and lead author of the study. -In addition, photogrammetry has the advantage of reproducing the colours 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,- she says. -Some parts of the flowers remain difficult to reconstruct in 3D, such as reflective, translucent or very hairy surfaces.-

Looking for answers

-We have shown that photogrammetry works at least as well as more complicated and expensive X-ray methods for visible flower structures,- says Université de Montréal professor Simon Joly, who conducts research at the Botanical Garden. -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.-

About this study

- Studying flowers in 3D using photogrammetry - by Marion Leménager et al., was published in New Phytologist. Financial support was provided by the Natural Sciences and Engineering Research Council of Canada and the Montreal Botanical Garden (Espace pour la vie).

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