To better understand the evolution of flowers, a research team in biology from Université de Montréal, the Montreal Botanical Garden and McGill University have succeeded in using photogrammetry to quickly and precisely build, in three dimensions, a model of a flower from two-dimensional images.
Flowers are the reproductive structures of angiosperm plants. They are typically brightly colored and have a distinctive aroma, which makes them attractive to pollinators such as bees, butterflies, and hummingbirds. Flowers are the plant’s way of reproducing, and the production of seeds is the ultimate goal of a flower’s existence. In addition to their reproductive function, flowers can also add beauty and aesthetic value to gardens and landscapes, and they are often used in floral arrangements and as gifts. Some flowers are also used for medicinal purposes, and others are used to make perfumes, essential oils, and other products. Overall, flowers play an important role in the plant world, and they are valued for their beauty and diversity.
The evolution of flowers is a complex and fascinating topic. Scientists are still working to understand the exact mechanisms and processes that led to the emergence of flowers. They first appeared on Earth about 140 million years ago. Prior to the evolution of flowers, plants reproduced using simple structures such as cones and spores. Today, there are more than 300,000 known species of flowering plants, and they are found in almost every habitat on Earth. The development of flowers allowed plants to reproduce in a more efficient and effective way, and this played a key role in the success and diversification of angiosperm plants and continues to be an area of active research and study.
Photogrammetry is commonly used by geographers to reconstruct the topography of a landscape. However, this is the first time that scientists have used the technique to design 3D models of flowers in order to better study them.
They results of their experiment were published in October in the journal New Phytologist.
Photogrammetry is a technique used to measure and analyze objects and spatial relationships using photographs. This can be done using a single photograph, or by combining multiple photographs taken from different angles. Photogrammetry allows for the accurate and precise measurement of objects and their positions in space, and it is often used in fields such as surveying, cartography, and architecture. Thanks to the triangulation of common points present on the photos, it is possible to reconstruct a 3D model — in this case, of a flower. Colours can then be applied to the 3D flower using information from the photos.
Attracting pollinators by shape and colour
Flowers are complex and extremely varied three-dimensional structures. Characterizing their forms is important in order to understand their development, functioning and evolution. Indeed, 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 in order to attract them. These features help to ensure the reproduction of the plant by facilitating the transfer of pollen from the male reproductive organs (stamen) to the female reproductive organs (pistil) of the flower.
For example, some flowers have elongated tubes that are well-suited for the proboscises of certain insects, while others have large, flat surfaces that are easier for birds and bats to land on. Therefore, the shape, size, and orientation of the flowers, as well as the movement patterns of the pollinators, all play a role in the ability of the pollinators to successfully transfer pollen from one flower to another. Yet the 3D structure of flowers is rarely studied.
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 Marion Leménager, a doctoral student in biological sciences at UdeM 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.”
It was Daniel Schoen, a McGill biology professor, who first had the idea of applying photogrammetry to flowers, while doing research at Institut de recherche en biologie végétale. The first results, although imperfect, were enough to convince Leménager to devote a chapter of her thesis to it.
“The method is not perfect,” she said. “Some parts of the flowers remain difficult to reconstruct in 3D, such as reflective, translucent or very hairy surfaces.”
Answering questions on flowers’ evolution
“That said,” added UdeM biology professor Simon Joly, “thanks to the living collections of the Montreal Botanical Garden, the study of plants of the Gesneriaceae family — plants originating from subtropical to tropical regions, of which the African violet is one of the best known representatives — demonstrates that 3D models produced using this technique make it possible to explore a large number of questions on the evolution of the shape and colour of flowers.
“We have also shown that photogrammetry works at least as well as X-ray methods for visible flower structures,” said Joly, who conducts research at the Botanical Garden.
Photogrammetry has the potential to boost research on flower evolution and ecology by providing a simple way to access three-dimensional morphological data, the researchers believe. Databases of flowers — or even of complete plants — could give scientists and the general public a way to see the unique features of plant species that for now remain hidden.
An open-access, detailed protocol has been made available to promote the use of this method in the context of the comparative study of floral morphology. The goal of free access to natural science collections of this sort is to help stimulate the study of the evolution of flower morphology at large taxonomic, temporal and geographical scales.
It is also possible to admire flower models from every angle thanks to a 3D model viewer.