To the root of it all
UPEI Dean of Science delves into leaf development.
On the surface, two sister plants that grow in the Amazon look somewhat alike.
But the definite differences that set Cecropria obtusa and Cecropia sciadophylla apart are what capture the scientific attention of Christian Lacroix, professor in biology at UPEI, who is currently acting as vice- president in charge of academic affairs.
In fact, he has spent time trekking through the Amazonian rainforest in French Guiana in search of specimens to study at a microscopical level to determine when exactly in the earliest moments of development that the plants take on their unique traits.
“I’m interested in the initiation of shape,” says Lacroix. “So how, for example, a maple leaf gets its lobes. How you can recognize a maple leaf from another leaf? I am interested in the very early events that generate that form.”
Lacroix is collaborating with Denis Barbabé from the University of Montréal, who has had a long- standing working relationship with his colleagues in French Guiana.
They have been collaborating for a number of years on a project that deals with the floral morphology of Aroids from the plant family, Araceae.
These studies focus on the development of flowers and the initiation of floral forms in this family, which consists of more than 3,500 species.
To date, they’ve been able to document unique modes of floral development and confirm the family tree of many species.
This past spring, Lacroix made his third trip to a research centre in the Peti Sault reservoir in the Amazon to collect samples of Cecropria that grow abundantly in the region.
He is now studying these specimens in the laboratory at UPEI using a scanning electron microscope.
“The current project that we’re working on, we went there specifically to collect two ( Cecropria) plants and those two ( sister) species have very similar leaf shapes, but yet they are very different . . . . ,” Lacroix says.
“One has a leaf that’s lobed . . . , the other one is a compound leaf; it looks very similar but it has individual and separate units on it.”
Because the plants are similar in the very early stages, Lacroix hopes to pinpoint when they diverge to produce a leaf that has many units versus a whole leaf that is lobed.
“I’m interested in how the cells divide to form the final shape because initially these cells form a small bump. And that bump begins to transform itself; that little bump produces more little bumps and eventually you start to recognize a shape. It’s embryonic development, but in plants,” he says.
In a lot of cases, sister species will share common pathways, much like a human fetus is neither male nor female until a very specific point in its development.
“It’s the very same in plants; until a certain point things look all the same and then at a certain point this leaf will take the path that it’s programmed to do . . . . So we’re interested in those step events and when the trigger happens . . . ,” Lacroix says.
“We’re just beginning to look at them now and it looks like they’re sharing a common pathway to a certain point. One has more units on it than the other. In this particular case, the two forms diverge fairly early on.
This plant study is a longterm project funded by the Natural Sciences and Engineering Research Council of Canada, the results of which will eventually be published in scientific journals.