The herbarium that Brother Marie-Victorin started in 1920 now has 750,000 specimens of plants and mosses from North and South America, the Caribbean, Europe, Africa, the Asia, Oceania and Australia, of which 150,000 were integrated by Marie-Victorin himself and his close collaborators. Today, it is the third largest herbarium in Canada, to which researchers in botany, ecology and the environment around the world refer in their work.
This collection has been stored since 2013 in two rooms of the Biodiversity Center of the Université de Montréal, which adjoins the Botanical Garden, where a temperature of 16°C and a humidity of 35% prevail, conditions that compromise the life cycle. a small winged beetle that delights in herbarium plants, says Geoffrey Hall, collections coordinator at the Center for Biodiversity.
The herbarium is an extraordinary wealth for researchers who want to know, for example, if a species of plant which seems to have appeared recently in a region was present there a hundred years ago. Or, conversely, if a plant like the pitcher plant, which today cannot be found on the island of Montreal, thrived in the bogs of Montreal a hundred years ago.
“With climate change, flowers of some species are also expected to bloom earlier and earlier in the spring and fruit later and later. In the herbarium, we have observable physical evidence of the time of year when a particular species flowered a hundred years ago. Many researchers use collections like ours to determine whether climate change has affected the flowering period over the past hundred years,” said Étienne Léveillé-Bourret, curator of the Marie-Victorin Herbarium.
The latter is interested in plant diversity, and more particularly in that of the papyrus family, the sedges, which includes the largest botanical genus in Canada, the sedge genus. “The Cyperaceae family is one of the richest in species, and as the flowers are tiny, the identification of these different species is very difficult”, explains Mr. Léveillé-Bourret who, with his student, will soon publish the description. of a new species of sedge.
“A few years ago, while sequencing the genome of all species of the sedge genus present in eastern North America with the aim of finding a method to identify the species, my thesis supervisor was realized that one of the specimens he had sequenced was genetically different from others of the same species. Looking more closely under the microscope, it was noticed that it was also morphologically different and had a different habitat. That’s what my student is clarifying,” says the curator.
The two researchers also traveled to Vietnam, another region of the world where sedges are abundant, to carry out a molecular phylogenetic study which aimed to determine the relationships between sedge species from North America and those from the United States. Southeast Asia and to draw up “the genealogy of these different species from their DNA”.
They thus discovered that the species that grow in Vietnam are very close relatives of those found in America and that they would be the ancestors of all the species present elsewhere in the world.
For her part, Geneviève Lajoie, researcher at the Montreal Botanical Garden and at the Institute for Research in Plant Biology (IRBV) of the University of Montreal, uses New England aster specimens from the Herbier Marie -Victorin that have been collected at different times over the past hundred years to measure the impact of climate change and urbanization on plant microbiota, comparing them to specimens collected today from various locations ranging from central -city of Montreal in Nominingue.
“Research on the plant microbiota is quite recent because we did not have the technological tools [d’analyse de l’ADN microbien] that allow us today to identify all the microbes that live in association with plant tissues,” says Ms.me Joy.
A wide variety of microbes carried by the wind and rain live on the surface of the leaves. Some of them enter the leaf tissues through the stomata, those small openings through which the plant breathes. Soil bacteria can also be translocated to the leaves.
Moreover, when it is opened, the flower accumulates bacteria which come to it in particular from the insects which pollinate it, and when the pollen fertilizes the ovule of the flower, the seed which is then formed in the fruit preserves these bacteria which will be found in the tissues of the new plant that will emerge from seed the following year.
Many bacteria live in symbiosis with the plant in a mutually beneficial relationship. “The leaf microbiota protects the plant by forming a physical barrier, a biofilm, which prevents the colonization of pathogens, and also by the secretion of antibiotic compounds which will kill harmful bacteria”, explains M.me Joy.
Still other bacteria secrete growth hormones or fix nitrogen and thus provide an additional source of this element which the tree needs to grow.
The great challenges of M researchme Lajoie are the contamination and the state of preservation of the specimens. To ensure that what is measured corresponds to the plant microbiota and does not result from contamination by the human microbiota during manipulations of the plant, a doctoral student takes samples from the same plant, some in a sterile and others with his hands, as we have always done. It then determines the microbial composition of these different specimens. Then, in a year, she will again characterize the composition of the microbiota of these specimens in order to observe the effect of storage and handling on it.
During our visit to the laboratories of the Marie-Victorin Herbarium, student Florence Lemay was cutting the tiny dried fruits of Victorin’s water-hemlock, a species discovered by Marie-Victorin which is now designated as “threatened species at the provincial level, and federally protected. “The problem is that this plant is very difficult to identify. We are trying to protect something that is hard to recognize! underlines Mr. Léveillé-Bourret. This is why Mrs. Lemay examines the inside of the fruit in the hope of finding distinctive characteristics.